17-hydroxyprogesterone is a steroid building block made mostly by the adrenal glands, with smaller amounts from the ovaries and testes. It sits midway in the body’s pathway for making cortisol, the main stress hormone. The molecule is created when progesterone is modified by a specific adrenal enzyme (17α-hydroxylase, CYP17A1). At home blood testing is available in select states. See FAQs below

Anti-Müllerian hormone is a signaling protein made by the ovaries’ small, growing egg sacs (granulosa cells of preantral and small antral follicles). It’s called “anti-Müllerian” At home blood testing is available in select states. See FAQs below

Cardio IQ Insulin blood testing measures the amount of insulin circulating in your blood. Insulin is a protein hormone (peptide) made by beta cells in the pancreas (islets of Langerhans). Rising blood sugar prompts these cells to process a precursor (proinsulin) and release insulin, along with C-peptide, into the circulation. At home blood testing is available in select states. See FAQs below

DHEA-S is the sulfated, storage form of the hormone DHEA made mainly by the adrenal glands. In blood, it appears as a stable pool that the body can draw on. Most DHEA-S comes from the adrenal cortex (zona reticularis), with smaller contributions from the ovaries or testes and the brain. At home blood testing is available in select states. See FAQs below

Estradiol blood testing measures the principal estrogen in the body, estradiol. This steroid hormone is made mainly by the ovaries before menopause, in smaller amounts by the testes, and to a lesser degree by the adrenal glands and body fat through conversion of androgens (aromatization). During pregnancy, the placenta becomes a major source. At home blood testing is available in select states. See FAQs below

Estradiol is the body’s primary estrogen (17β‑estradiol, E2). It is made mainly in the ovaries, with smaller amounts produced in fat tissue and the adrenal glands via aromatase, and in the testes in men; during pregnancy, the placenta becomes a major source. At home blood testing is available in select states. See FAQs below

Follicle Stimulating Hormone (FSH) is a signaling hormone in your bloodstream, made by the front part of the pituitary gland at the base of the brain (anterior pituitary gonadotropin). Specialized pituitary cells release FSH under cues from the brain (gonadotropin-releasing hormone, GnRH). At home blood testing is available in select states. See FAQs below

The Free Androgen Index (FAI) is a calculated number derived from a blood test; it is not a hormone itself. It uses two measured players: total testosterone, the main androgen made primarily by the testes or ovaries and also by the adrenal glands, and sex hormone–binding globulin (SHBG), a transport protein produced by the liver. At home blood testing is available in select states. See FAQs below

Plasma glucose is the amount of simple sugar (glucose) dissolved in the liquid part of your blood (plasma). It comes from the digestion and absorption of carbohydrates in the small intestine and from your liver, which releases glucose by breaking down stored glycogen and by making new glucose from non‑carbohydrate sources (glycogenolysis, gluconeogenesis). At home blood testing is available in select states. See FAQs below

Luteinizing hormone (LH) is a chemical messenger made in the front part of the pituitary gland in the brain (anterior pituitary). Its release is prompted by signals from the hypothalamus (gonadotropin-releasing hormone, GnRH). LH is a glycoprotein produced by specialized pituitary cells (gonadotrophs). At home blood testing is available in select states. See FAQs below

ANA stands for antinuclear antibodies—antibodies that target molecules inside the cell nucleus. They are not a single substance but a family of self‑reactive antibodies made by immune B cells when tolerance to the body’s own tissues slips. These antibodies circulate in the bloodstream and can bind DNA, histones, and nuclear proteins (nuclear antigens). At home blood testing is available in select states. See FAQs below

Basophils blood testing looks at a rare class of white blood cell called the basophil. Basophils form in the bone marrow and circulate in the bloodstream with granules packed with fast-acting chemical signals (granulocyte; histamine, heparin, leukotrienes). The test simply measures how many basophils are present in your blood at a given time (basophil count/percentage), offering a window into this small but potent immune cell population. At home blood testing is available in select states. See FAQs below

Basophils, Absolute—Blood Testing measures the actual number of basophils circulating in your blood. Basophils are a rare subset of white blood cells (leukocytes) loaded with dark granules (granulocytes). They are produced in the bone marrow from hematopoietic stem cells along the myeloid lineage and then released into the bloodstream. At home blood testing is available in select states. See FAQs below

CCP antibody blood testing looks for antibodies your immune system makes against small protein fragments called cyclic citrullinated peptides. These peptides appear when an enzyme changes one protein building block (arginine) into citrulline during inflammation (citrullination by peptidylarginine deiminase, PAD). At home blood testing is available in select states. See FAQs below

The Celiac Disease Comprehensive Panel gauges whether your immune system is mounting an autoimmune response to gluten that damages the small intestine. By measuring celiac‑specific antibodies (such as tissue transglutaminase and endomysial) alongside total IgA, it connects gut integrity with nutrient absorption, blood health, bone strength, skin, nerves, and even fertility and growth. At home blood testing is available in select states. See FAQs below

Anti–double-stranded DNA antibodies are immune proteins that bind the body’s own DNA. They are autoantibodies (anti‑dsDNA) produced by B cells that have lost self‑tolerance, often after nuclear material from dying cells is exposed. These antibodies circulate in the blood and recognize native double‑stranded DNA (dsDNA) from the cell nucleus. At home blood testing is available in select states. See FAQs below

Eosinophils are a specialized type of white blood cell (granulocytic leukocytes) made in the bone marrow. After maturing, they pass through the bloodstream briefly before settling in tissues, especially the gut, lungs, and skin. An eosinophil blood test measures how many of these cells are circulating at a given moment. At home blood testing is available in select states. See FAQs below

Eosinophils, Absolute is the measured number of eosinophils circulating in your blood. Eosinophils are a specialized type of white blood cell (granulocyte) made in the bone marrow under signals such as interleukin‑5 (IL‑5). They contain enzyme‑filled packets (cytoplasmic granules) that stain reddish‑orange and circulate briefly before moving into tissues like the lungs, gut, and skin. At home blood testing is available in select states. See FAQs below

The Lymphocyte-to-Monocyte Ratio (LMR) is a simple snapshot of immune balance in the bloodstream. It compares the number of lymphocytes to the number of monocytes, both types of white blood cells (leukocytes) measured on a standard differential count. Lymphocytes are the targeted, memory-building cells of the immune system (T cells, B cells, and natural killer cells), born in the bone marrow and maturing in lymphoid organs such as the thymus and lymph nodes. At home blood testing is available in select states. See FAQs below

Lymphocytes blood testing measures how many lymphocytes are circulating in your blood. Lymphocytes are a major type of white blood cell born in the bone marrow from blood-forming stem cells (hematopoietic stem cells). They include B cells, T cells, and natural killer cells (B lymphocytes, T lymphocytes, NK cells). At home blood testing is available in select states. See FAQs below

Asymmetric dimethylarginine (ADMA) is a small molecule made when the body modifies certain proteins during normal cell activity. Enzymes add methyl groups to arginine side chains in proteins (protein arginine methyltransferases, PRMTs). When those proteins are broken down, free ADMA is released into the bloodstream. At home blood testing is available in select states. See FAQs below

Apolipoprotein B (ApoB) blood testing measures the amount of ApoB, the main scaffold protein on the body’s fat‑carrying particles in blood (apolipoprotein B on circulating lipoproteins). ApoB is made in the liver and intestine, appearing as two forms: ApoB‑100 from the liver and ApoB‑48 from the gut. At home blood testing is available in select states. See FAQs below

The Atherogenic Coefficient (AC) is a calculated marker from a standard cholesterol blood test, not a substance in the blood. It describes how cholesterol is distributed among lipoproteins. Specifically, it compares the cholesterol carried by potentially plaque-forming particles (non-HDL lipoproteins: LDL, VLDL, IDL, and remnants) to the cholesterol carried by the protective scavenger particle (HDL). At home blood testing is available in select states. See FAQs below

The Atherogenic Index of Plasma (AIP) is a calculated snapshot of your blood’s lipid mix. It combines two routine lipid values—triglycerides and HDL cholesterol—to summarize how fats made in the liver and absorbed from the gut travel in the bloodstream inside carrier particles (lipoproteins). At home blood testing is available in select states. See FAQs below

The cholesterol/HDL ratio blood test reports a calculated indicator from a standard lipid panel. It compares the amount of cholesterol circulating in all particles combined (total cholesterol) with the portion carried by the “scavenger” particles that help ferry cholesterol away from tissues (HDL cholesterol). At home blood testing is available in select states. See FAQs below

Total cholesterol blood testing measures the overall amount of cholesterol circulating in your blood. Cholesterol is a waxy, fat-like molecule (sterol lipid) that your body makes mainly in the liver and also absorbs from animal-based foods. At home blood testing is available in select states. See FAQs below

Cystatin C is a small protein that all your body’s cells release into the bloodstream at a steady rate (cysteine protease inhibitor made by nucleated cells). The kidneys filter it out through the glomeruli, and the filtered protein is then taken up and broken down by the tubules, so it doesn’t return to the blood. At home blood testing is available in select states. See FAQs below

HDL cholesterol in a blood test is the amount of cholesterol carried inside high-density lipoproteins. These are tiny, protein‑rich particles made mainly by the liver and small intestine (HDL particles containing apolipoprotein A‑I). HDL is part of the body’s lipoprotein system that transports fats through the blood. At home blood testing is available in select states. See FAQs below

HDL-P blood testing measures the number of high-density lipoprotein particles circulating in your blood. HDL particles are tiny lipid-protein carriers built around apolipoprotein A‑I (apoA‑I) and a shell of phospholipids and cholesterol. They arise from the liver and intestine and then assemble and mature in the bloodstream as they pick up fats and cholesterol from tissues. At home blood testing is available in select states. See FAQs below

HDL Size blood testing gauges the average diameter of high-density lipoprotein particles circulating in your blood. HDL particles are tiny lipid–protein packages built primarily in the liver and intestine (hepatic, intestinal origin). They start as small, lipid‑poor discs centered on apolipoprotein A‑I (apoA‑I) and grow as they collect cholesterol from cells; enzymes and transfer proteins reshape them along the way, notably LCAT (lecithin–cholesterol acyltransferase), CETP (cholesteryl ester transfer protein), and hepatic lipase. At home blood testing is available in select states. See FAQs below

Cortisol is the body’s primary stress-response hormone, made by the adrenal cortex and guided by the brain’s HPA axis. It mobilizes fuel, maintains blood pressure and vascular tone, tempers inflammation, and fol At home blood testing is available in select states. See FAQs below

Cortisol-to-DHEA-S ratio blood testing compares two adrenal hormones in your bloodstream. Cortisol is the body’s primary stress hormone, made in the adrenal cortex’s middle layer (zona fasciculata) in response to adrenocorticotropic hormone (ACTH). DHEA-S is the stable, circulating form of DHEA (dehydroepiandrosterone sulfate), produced mainly in the inner layer (zona reticularis). At home blood testing is available in select states. See FAQs below

Ferritin blood testing measures ferritin—the body’s primary iron‑storage protein—in the circulation. Ferritin is made inside cells throughout the body, especially in the liver, spleen, and bone marrow, where iron is stored and recycled (hepatocytes and macrophages of the reticuloendothelial system). Its protein shell (apoferritin) holds iron safely in a mineral form (ferric iron). At home blood testing is available in select states. See FAQs below

Iron saturation is the share of your blood’s iron‑transport protein that is actually carrying iron at a given moment. In scientific terms, it is transferrin saturation (TSAT): the percentage of transferrin, a protein made by the liver, with its iron‑binding sites filled. At home blood testing is available in select states. See FAQs below

Total Iron blood testing measures the amount of iron circulating in the liquid part of your blood, almost all of it carried by the transport protein transferrin. This circulating iron comes from two sources: iron absorbed from food in the small intestine and iron recycled from worn‑out red blood cells by cleanup cells in the spleen and liver (macrophages). At home blood testing is available in select states. See FAQs below

The RDW/Ferritin ratio is a combined blood index that relates red blood cell size variability (red cell distribution width, RDW) to the body’s iron reserves (serum ferritin). RDW comes from the standard blood count and describes how uniform or mixed in size your circulating red cells are (anisocytosis). At home blood testing is available in select states. See FAQs below

Total iron binding capacity (TIBC) is a measure of how much iron your blood could carry if all of its transport slots were filled. It mainly reflects the amount of transferrin, the iron-transport protein made by the liver (transferrin, a glycoprotein produced by hepatocytes). At home blood testing is available in select states. See FAQs below

Folate is a water-soluble B vitamin your body cannot make on its own (vitamin B9; folates). You get it from food—especially leafy greens, legumes, and fortified grains—or as folic acid in supplements. After absorption in the small intestine, the body converts it into active forms (tetrahydrofolate, THF) and stores a small amount in the liver. At home blood testing is available in select states. See FAQs below

Folate blood testing measures the amount of folate (vitamin B9) circulating in your blood. Folate is an essential, water‑soluble nutrient the body cannot make; you get it from foods and supplements (folic acid). After absorption in the small intestine, it is converted to active forms—mainly 5‑methyltetrahydrofolate (5‑MTHF)—and carried to tissues. At home blood testing is available in select states. See FAQs below

Folate, RBC is a measure of the folate stored inside your red blood cells. Folate is a B vitamin from food (vitamin B9) absorbed in the small intestine and converted into active forms (tetrahydrofolate, 5‑methyltetrahydrofolate). As red blood cells are produced in the bone marrow (erythropoiesis), they take up folate and keep it for their lifespan. At home blood testing is available in select states. See FAQs below

Homocysteine is a sulfur‑containing amino acid your body makes as it breaks down methionine from dietary protein. It is not taken in from food; it appears briefly inside cells as a crossroads in the methionine cycle. From there, it can be recycled back to methionine using folate and vitamin B12 (remethylation via 5‑methyltetrahydrofolate and methionine synthase), or shunted toward making cysteine using vitamin B6 (transsulfuration via cystathionine β‑synthase). At home blood testing is available in select states. See FAQs below

Homocysteine blood testing measures the level of homocysteine, a sulfur-containing amino acid that appears as a normal byproduct when the body uses methionine from protein. Homocysteine is made inside cells and briefly circulates in the blood before being recycled back to methionine or converted into cysteine and glutathione. At home blood testing is available in select states. See FAQs below

Methylmalonic acid (MMA) is a small organic acid your body produces while breaking down certain proteins and fats. It forms inside mitochondria during the propionate pathway, where fragments from odd‑chain fatty acids and specific amino acids are converted toward energy use. At home blood testing is available in select states. See FAQs below

Vitamin B12 blood testing measures the amount of vitamin B12 carried in your bloodstream. Vitamin B12 (cobalamin) is an essential nutrient obtained from animal-based foods and supplements. After eating, stomach acid frees B12 from food; it binds to a stomach-made carrier called intrinsic factor and is absorbed in the last part of the small intestine (ileum). At home blood testing is available in select states. See FAQs below

Vitamin B12 powers cell division, red blood cell production, and the maintenance of myelin—the insulation on nerves. A blood B12 test is a readout of the body’s capacity to make DNA efficiently, carry oxygen, and keep the brain and peripheral nerves functioning smoothly. At home blood testing is available in select states. See FAQs below

Vitamin B2 (riboflavin) blood testing measures the amount of riboflavin circulating in your blood, largely present in its active forms. Riboflavin is a water‑soluble B vitamin your body cannot store well and must obtain from the diet. After absorption in the small intestine, it travels in the bloodstream mainly as flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are taken up by tissues as needed. At home blood testing is available in select states. See FAQs below

Vitamin B6 (plasma) is the amount of vitamin B6 circulating in your blood. Vitamin B6 is a water‑soluble nutrient you get from food and supplements. After absorption in the small intestine, the liver converts it into its active coenzyme forms, mainly pyridoxal 5′‑phosphate (PLP) and to a lesser extent pyridoxamine phosphate (PMP), derived from the parent compounds pyridoxine, pyridoxal, and pyridoxamine. At home blood testing is available in select states. See FAQs below

Insulin-like growth factor 1 (IGF-1) is a protein hormone that circulates in the bloodstream and carries out growth signals. Most IGF-1 is made by the liver after stimulation from growth hormone released by the pituitary gland. Many tissues also make small amounts locally. At home blood testing is available in select states. See FAQs below

The CRP/Albumin Ratio (CAR) is a blood test calculation that compares two liver-made blood proteins. C-reactive protein (CRP) is released by the liver when the immune system detects inflammation or tissue damage. Serum albumin (albumin) is the most abundant protein in the bloodstream, produced by liver cells and responsible for maintaining fluid balance and carrying hormones, fatty acids, and drugs. At home blood testing is available in select states. See FAQs below

The CRP/DHEA‑S ratio is a composite blood marker that compares two signals: C‑reactive protein (CRP) and dehydroepiandrosterone sulfate (DHEA‑S). CRP is an acute‑phase protein made by the liver when inflammatory messengers rise (interleukin‑6 and related cytokines). DHEA‑S is the sulfated, long‑circulating form of the adrenal androgen DHEA, produced in the adrenal cortex (zona reticularis) and acting as a hormone precursor pool that tissues can draw on. At home blood testing is available in select states. See FAQs below

The CRP-to-lymphocyte ratio (CLR) is a composite blood marker built from two routine measures: C‑reactive protein and the circulating lymphocyte count. CRP is a soluble protein made by the liver (hepatocytes) when pro‑inflammatory cytokines, especially interleukin‑6, trigger the acute-phase response. At home blood testing is available in select states. See FAQs below

Erythrocyte Sedimentation Rate (ESR) is a blood test index that reflects how readily red blood cells (erythrocytes) settle within the liquid part of blood (plasma). It is driven by the mix of proteins in plasma, especially those released by the liver and immune system during stress or illness (fibrinogen, immunoglobulins, complement). At home blood testing is available in select states. See FAQs below

The Ferritin/CRP ratio is a composite blood marker that compares two liver‑linked proteins. Ferritin is the body’s iron‑storage protein (intracellular ferritin) concentrated in liver cells and macrophages; a small amount circulates and mirrors stored iron. C‑reactive protein is an inflammation signal (acute‑phase protein) made by the liver in response to immune messengers such as interleukin‑6. At home blood testing is available in select states. See FAQs below

The Ferritin-to-Albumin Ratio (FAR) is a composite blood marker that compares two familiar proteins. Ferritin is the body’s iron storage protein, mainly kept inside liver and immune cells and released into the bloodstream in small amounts (ferritin; hepatocytes; macrophages). Albumin is the principal protein made by the liver that circulates in plasma and carries many substances (albumin; hepatic synthesis; plasma protein). At home blood testing is available in select states. See FAQs below

High-sensitivity C-reactive protein (hs-CRP) blood testing measures the amount of C-reactive protein circulating in your bloodstream. CRP is a protein made in the liver (hepatocytes) when the immune system sends inflammatory signals, especially interleukin‑6. It is part of the acute-phase response, the body’s rapid, coordinated reaction to injury or infection. At home blood testing is available in select states. See FAQs below

Monocyte-to-HDL Ratio (MHR) blood testing calculates the proportion of monocytes to high-density lipoprotein in circulation. Monocytes (innate immune white blood cells) are made in the bone marrow and travel in the bloodstream before moving into tissues, where they can mature into macrophages. At home blood testing is available in select states. See FAQs below

The platelet-to-lymphocyte ratio (PLR) is a derived biomarker calculated from a routine blood count. It compares the number of platelets to the number of lymphocytes circulating in your blood. Platelets (thrombocytes) are small cell fragments made in the bone marrow from megakaryocytes, ready to plug leaks and release inflammatory signals. At home blood testing is available in select states. See FAQs below

The Systemic Immune-Inflammation Index (SII) is a composite blood marker that blends information from three circulating cell types: neutrophils, lymphocytes, and platelets. All three are born in the bone marrow and constantly patrol the bloodstream. Neutrophils are front-line defenders (innate immune cells), lymphocytes coordinate targeted defense and memory (adaptive immune cells), and platelets (thrombocytes) help with clotting and signal at sites of injury. At home blood testing is available in select states. See FAQs below

Blood Urea Nitrogen (BUN) is the amount of nitrogen in your blood that comes from urea, the main waste product formed when your body breaks down protein. The liver (hepatocytes) converts ammonia—a toxic byproduct of protein metabolism—into urea via the urea cycle, making it safe to carry in the bloodstream. At home blood testing is available in select states. See FAQs below

The BUN/creatinine ratio is a comparison of two common blood wastes: urea nitrogen and creatinine. Urea nitrogen (BUN) comes from urea made in the liver as it detoxifies ammonia generated when proteins are broken down (urea cycle). Creatinine is formed at a steady rate as muscles use and renew creatine phosphate. At home blood testing is available in select states. See FAQs below

Calcium blood testing measures the amount of calcium circulating in your bloodstream. Most of your body’s calcium is locked into bone and teeth as a hard mineral (hydroxyapatite). A small fraction travels in blood in two forms: free, biologically active calcium (ionized Ca2+) and calcium attached to proteins or small molecules (protein-bound and complexed). At home blood testing is available in select states. See FAQs below

Carbon dioxide (CO2) blood testing reports the total CO2 in your blood, which mostly reflects bicarbonate, the body’s main base. In standard chemistry panels this “CO2” is predominantly bicarbonate (HCO3−), with small amounts of dissolved CO2 and carbonic acid (H2CO3). CO2 is made continuously as your cells burn carbohydrates and fats for energy. At home blood testing is available in select states. See FAQs below

Chloride in blood is the chloride ion, a negatively charged electrolyte (anion) dissolved in the fluid outside your cells (extracellular fluid). It comes mainly from dietary salt (sodium chloride), is absorbed in the gut, and circulates in the bloodstream. The kidneys regulate chloride continuously, deciding how much to keep or excrete in response to hormones and the body’s acid–base needs. At home blood testing is available in select states. See FAQs below

Cockcroft-Gault creatinine clearance blood testing is a calculated estimate of how effectively your kidneys filter a muscle‑derived waste called creatinine out of the blood. Creatinine comes from normal muscle energy use (breakdown of creatine phosphate), enters the bloodstream at a fairly steady rate, and is removed by the kidney’s filtering units (glomeruli) into urine. At home blood testing is available in select states. See FAQs below

Creatinine is a small waste molecule made when your muscles use creatine for energy. It forms at a steady pace linked to muscle mass as creatine and phosphocreatine break down in skeletal muscle, then enters the bloodstream. The body doesn’t use creatinine; it is transported to the kidneys and eliminated in urine. At home blood testing is available in select states. See FAQs below

Estimated glomerular filtration rate, or eGFR, is a calculated indicator of how much blood your kidneys filter each minute. It is not a substance in your blood but a number derived from a routine blood test. The calculation uses the level of creatinine (a waste product from muscle activity) and sometimes cystatin C (a small protein made by most cells), combined with your age and sex, to estimate the filtering work done by the kidney’s tiny sieves (glomeruli). At home blood testing is available in select states. See FAQs below

Potassium Blood Testing measures the amount of potassium circulating in your blood (serum potassium, K+). Potassium is an essential mineral and electrolyte (a positively charged ion, or cation) that lives mainly inside your body’s cells. It enters the body from food, is absorbed in the gut, moves into and out of cells under hormonal signals (insulin, catecholamines), and is finely regulated by the kidneys under the influence of aldosterone. At home blood testing is available in select states. See FAQs below

Blood sodium testing measures the amount of sodium, a charged mineral (electrolyte), in the liquid part of your blood. Sodium comes from your diet—mainly table salt (sodium chloride)—and after absorption in the gut it lives mostly in the fluid outside cells (extracellular fluid). At home blood testing is available in select states. See FAQs below

Alanine aminotransferase (ALT) is an enzyme kept mainly inside liver cells (hepatocytes). Smaller amounts exist in the kidneys, heart, and skeletal muscle. An ALT blood test measures how much of this normally inside-the-cell enzyme is found in the bloodstream. At home blood testing is available in select states. See FAQs below

Albumin blood testing measures albumin, the main protein in the liquid part of your blood. Albumin is made by the liver (hepatocytes) and released into the bloodstream (plasma). It is a compact, globular carrier protein (serum albumin) that circulates widely through blood and tissues. At home blood testing is available in select states. See FAQs below

The albumin/globulin ratio (A/G ratio) is a calculated index from a standard blood protein panel. It compares albumin—the dominant plasma protein made by the liver—to the combined globulins, a broad family of proteins that includes transport proteins and antibodies. Albumin is synthesized by hepatocytes, while alpha and beta globulins are mainly liver-derived and gamma globulins (immunoglobulins) are produced by plasma cells. At home blood testing is available in select states. See FAQs below

Alkaline Phosphatase (ALP) blood testing measures the amount of ALP, a surface enzyme attached to cell membranes throughout the body. Most circulating ALP comes from the liver and bile ducts (hepatocytes and cholangiocytes) and from bone-forming cells (osteoblasts). Smaller contributions can come from the intestine, kidney, and—in pregnancy—the placenta. At home blood testing is available in select states. See FAQs below

Aspartate aminotransferase (AST) is a naturally occurring enzyme inside many tissues, most abundantly the liver, but also the heart, skeletal muscle, kidneys, brain, and red blood cells. It resides in both the watery part of the cell and its energy factories (cytosol and mitochondria). At home blood testing is available in select states. See FAQs below

Bilirubin, Direct (blood testing) measures the fraction of bilirubin that has been processed by the liver and made water‑soluble. Bilirubin itself is a yellow pigment created as the body breaks down old red blood cells. Macrophages convert heme from hemoglobin into bilirubin (unconjugated, indirect), which is carried to the liver bound to albumin. At home blood testing is available in select states. See FAQs below

Indirect bilirubin is the form of bilirubin circulating before the liver modifies it. Bilirubin is a yellow pigment created when old red blood cells are dismantled; hemoglobin’s heme ring is opened to biliverdin, then reduced to bilirubin (unconjugated bilirubin). This fat‑soluble molecule leaves the spleen and other tissues attached to albumin and travels in the bloodstream to the liver. At home blood testing is available in select states. See FAQs below

The Bilirubin-to-Albumin Ratio (BAR) is a calculated number that compares the amount of the yellow pigment made when red blood cells are broken down (bilirubin) with the amount of the main carrier protein in blood (albumin). Bilirubin is produced from heme in the spleen and other tissues, released into the bloodstream in an unconjugated form, and carried to the liver while bound to albumin. At home blood testing is available in select states. See FAQs below

Bilirubin is a yellow pigment made when the body recycles worn‑out red blood cells. Macrophages in the spleen and liver break down hemoglobin’s heme into biliverdin and then bilirubin. This first form, called unconjugated bilirubin (indirect bilirubin), is not water‑soluble and travels in the bloodstream bound to albumin. At home blood testing is available in select states. See FAQs below

The De Ritis ratio is the proportion of two liver-related enzymes measured in blood: aspartate aminotransferase (AST) and alanine aminotransferase (ALT). These enzymes are catalysts in amino acid metabolism (transaminases). ALT is concentrated in liver cells (hepatocytes) and mainly resides in the cell fluid (cytosol). At home blood testing is available in select states. See FAQs below

Hematocrit blood testing measures the share of your blood made up by red blood cells. It’s a property of whole blood, capturing how much space the red cells (erythrocytes) occupy relative to the liquid portion (plasma). These cells are produced in the bone marrow under signals from the kidneys’ hormone erythropoietin (EPO) and are filled with hemoglobin, the protein that binds oxygen. At home blood testing is available in select states. See FAQs below

Hemoglobin blood testing measures the amount of hemoglobin, the red, oxygen‑carrying protein inside your red blood cells (erythrocytes). Hemoglobin is made in the bone marrow as new red blood cells are formed (hematopoiesis). Each hemoglobin molecule holds iron within heme groups and sits packed inside circulating red blood cells, which is why the test is done on blood. At home blood testing is available in select states. See FAQs below

Magnesium blood testing measures the amount of magnesium circulating in the liquid part of your blood (serum magnesium). Magnesium is an essential mineral and electrolyte. You get it from food and water; it’s absorbed in the gut and distributed throughout the body. At home blood testing is available in select states. See FAQs below

Mean Corpuscular Hemoglobin Concentration (MCHC) is a red‑cell index that describes how concentrated the oxygen-carrying protein is inside a At home blood testing is available in select states. See FAQs below

Mean Corpuscular Hemoglobin (MCH) is the average amount of hemoglobin contained in each red blood cell. Hemoglobin is the iron-bearing protein that binds oxygen in the lungs and releases it to tissues. Red blood cells are formed in the bone marrow, where hemoglobin is packed into them as they mature. At home blood testing is available in select states. See FAQs below

Mean Corpuscular Volume (MCV) is the average size of your red blood cells. It is a property of the circulating red cell population measured from a routine blood sample, reported within the complete blood count (CBC). Red blood cells (erythrocytes) are formed in the bone marrow through red cell production (erythropoiesis) and released into the bloodstream; MCV captures their At home blood testing is available in select states. See FAQs below

Mean Platelet Volume (MPV) is the average size of your platelets—the tiny, anucleate cell fragments that help your blood clot. Platelets are shed from large bone‑marrow cells called megakaryocytes and circulate for several days before being cleared. MPV summarizes how big these circulating platelets are at a given time (platelet volume), offering a snapshot of their At home blood testing is available in select states. See FAQs below

Platelet count is the measured number of platelets (thrombocytes) circulating in your blood. Platelets are tiny, disc-shaped cell fragments produced in the bone marrow when large precursor cells (megakaryocytes) shed portions of their cytoplasm. Their production is guided by the hormone thrombopoietin from the liver. At home blood testing is available in select states. See FAQs below

Total blood protein is the combined amount of the major proteins circulating in your bloodstream. Most of it is albumin, made by the liver (hepatocytes), and globulins, made by both the liver and the immune system (immunoglobulins from plasma cells, plus transport and defense proteins). At home blood testing is available in select states. See FAQs below

The RDW/MCV ratio is a calculated index from a standard complete blood count. It divides the red cell distribution width (RDW)—a measure of how varied your red blood cells are in size—by the mean corpuscular volume (MCV), the average size of those cells. At home blood testing is available in select states. See FAQs below

Free T4 Index (FT4I, also called T7) is a calculated estimate of the amount of free thyroxine in your bloodstream. Thyroxine (T4) is a hormone made by the thyroid gland and released into blood mostly attached to carrier proteins (thyroxine‑binding globulin, transthyretin, albumin). At home blood testing is available in select states. See FAQs below

T3 uptake is a derived measure from a blood sample that estimates the carrying capacity of the blood for thyroid hormones. It does not measure triiodothyronine itself. Instead, it reflects how many binding sites on the blood’s thyroid hormone carrier proteins are available or already occupied. At home blood testing is available in select states. See FAQs below

Thyroglobulin antibodies are immune proteins your body makes that target thyroglobulin, a large protein produced only by thyroid cells. Thyroglobulin (Tg) sits inside the thyroid’s follicles as the scaffold on which thyroid hormones are built. When the immune system becomes misdirected, B cells create antibodies against this self-protein (autoantibodies), which then circulate in the bloodstream. At home blood testing is available in select states. See FAQs below

Thyroid peroxidase antibody testing looks for immune proteins that target a key thyroid enzyme. Thyroid peroxidase lives on the surface of thyroid hormone–making cells and helps attach iodine to the hormone’s building blocks. When the immune system produces antibodies against this enzyme, they circulate in the blood and can be measured. At home blood testing is available in select states. See FAQs below

Thyroid‑stimulating hormone is the body’s main signal that tells the thyroid what to do. It is made by the front part of the pituitary gland at the base of the brain (anterior pituitary) and released into the bloodstream. This hormone is also called thyrotropin (TSH). At home blood testing is available in select states. See FAQs below

Thyroxine is the primary hormone produced by the thyroid gland in the neck. A Total T4 blood test measures the full amount of thyroxine in circulation, combining the small fraction that is unbound with the larger fraction attached to carrier proteins (free and protein‑bound T4). At home blood testing is available in select states. See FAQs below

Triiodothyronine (T3) is the body’s most active thyroid hormone. It is produced in small amounts by the thyroid gland and largely formed throughout the body when enzymes remove an iodine atom from thyroxine (T4) in organs like the liver and kidneys (peripheral deiodination). At home blood testing is available in select states. See FAQs below

Adiponectin blood testing measures the level of adiponectin circulating in your blood. Adiponectin is a hormone-like protein (adipokine) made primarily by fat tissue (adipose tissue) and secreted by individual fat cells (adipocytes) into the bloodstream. At home blood testing is available in select states. See FAQs below

Cardio IQ Insulin Resistance blood testing is a cardiometabolic panel that estimates how resistant your body is to insulin (insulin resistance). It measures insulin produced by pancreatic beta cells alongside select metabolic signals released into the bloodstream by the liver, fat tissue, and circulating lipoproteins, then brings them together into a coherent picture of insulin action. At home blood testing is available in select states. See FAQs below

Corrected calcium (albumin‑adjusted calcium) is a calculated estimate that modifies your routine blood calcium to account for albumin, the main protein that carries calcium in the bloodstream. In blood, calcium exists in two forms: attached to proteins, chiefly albumin (protein‑bound), and unbound (ionized). At home blood testing is available in select states. See FAQs below

Estimated Average Glucose is a calculation that translates your long-term blood sugar pattern into a single everyday number. It is derived from hemoglobin A1c, the fraction of hemoglobin in red blood cells that becomes coated with sugar. Glucose circulating in your blood drifts into red blood cells and sticks to hemoglobin over time (non-enzymatic glycation). At home blood testing is available in select states. See FAQs below

Estimated Average Glucose (eAG) is a calculated value that translates hemoglobin A1c into an everyday blood sugar number. It arises from the way glucose in the bloodstream binds slowly and steadily to the hemoglobin protein inside red blood cells (erythrocytes). This attachment happens without enzymes (nonenzymatic glycation). At home blood testing is available in select states. See FAQs below

Estimated Glucose / HbA1c Ratio (Glycation Gap) blood testing compares your hemoglobin A1c with an independent estimate of your average blood glucose. Hemoglobin A1c (HbA1c) forms when glucose nonenzymatically attaches to hemoglobin inside red blood cells (erythrocytes) over their lifespan. At home blood testing is available in select states. See FAQs below

Fructosamine is the collective signal of sugars attached to blood proteins. In the bloodstream, glucose binds spontaneously to free amino groups on circulating proteins—mostly albumin—through nonenzymatic glycation (Maillard reaction), forming stable ketoamine adducts (fructosamines). A fructosamine blood test quantifies these glycated serum proteins, so the biomarker originates from the everyday interaction between glucose and the body’s protein pool in serum. At home blood testing is available in select states. See FAQs below

Blood glucose testing measures the amount of glucose—the simple sugar circulating in your bloodstream. Glucose originates from digestion of dietary carbohydrates in the small intestine and from the liver, which releases stored glucose (glycogenolysis) and creates new glucose from non‑carbohydrate sources (gluconeogenesis). At home blood testing is available in select states. See FAQs below

Hemoglobin A1c is hemoglobin with sugar attached. Inside red blood cells, glucose in the bloodstream slowly sticks to hemoglobin A, forming a stable sugar–hemoglobin adduct (non-enzymatic glycation of the beta-chain N-terminal valine, yielding a ketoamine called HbA1c). This happens continuously and irreversibly for as long as the red cell circulates. At home blood testing is available in select states. See FAQs below

Insulin blood testing measures the hormone insulin circulating in your bloodstream. Insulin is made by beta cells in the pancreas (pancreatic islet β‑cells). It is produced from a larger precursor (proinsulin) and released together with its companion fragment (C‑peptide). At home blood testing is available in select states. See FAQs below