Biomarkers

8-OHdG is a chemically damaged DNA building block, formed when reactive oxygen species (ROS) attack a specific spot on the guanine base. It is one of the most common and…

Albumin is the most abundant protein in your blood plasma, made only by your liver. It keeps fluid inside your blood vessels (colloid osmotic pressure) and ferries hormones,…

The albumin/globulin (A/G) ratio compares two groups of proteins in your blood. It is calculated as albumin divided by (total protein minus albumin). The 'globulin' part includes…

Alkaline phosphatase (ALP) is an enzyme that snips phosphate groups in an alkaline environment. The level in your blood is a mix of forms from several organs, mainly your liver,…

ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are enzymes inside your cells that spill into your blood when liver cells are injured. ALT is fairly…

Apolipoprotein A-I (ApoA-I) is the main protein of 'good' HDL cholesterol. Your liver and gut make it, and it makes up about 70% of HDL's protein. It switches on an enzyme (LCAT)…

Apolipoprotein B (ApoB) is the backbone protein of the 'bad' lipoproteins that clog arteries. These include LDL, VLDL, IDL, and Lp(a). Each such particle carries about one…

Apolipoprotein E (APOE) is a fat-transport protein, coded by the APOE gene. The gene comes in three versions (alleles): ε2, ε3, and ε4, giving six possible genotypes. The ε4…

The AST/ALT ratio (also called the De Ritis ratio, after Fernando De Ritis, who described it in the 1950s) is just one liver enzyme divided by another: AST divided by ALT. In…

Bilirubin is the yellow waste your body makes when it recycles old red blood cells. It travels in two forms. First it rides on a protein (albumin) as 'unconjugated', or indirect,…

C-peptide is a 31-amino-acid chain. It is cut out of proinsulin inside your pancreatic beta cells. One C-peptide is released for every insulin molecule. So your fasting C-peptide…

CA-125 (cancer antigen 125) is a large mucin-like protein made by the MUC16 gene. It sits on certain body-cavity and reproductive-tract surfaces. It sheds into your blood when…

Cell-free DNA (cfDNA) is short fragments of DNA floating in your blood plasma. They are released by cells that die, by apoptosis or necrosis. (The fragments are typically 140-200…

The coronary artery calcium (CAC) score comes from a non-contrast cardiac CT scan. It is reported as an 'Agatston score'. It measures how much calcified plaque is in your…

Cortisol is the main glucocorticoid (stress hormone) from your adrenal glands. It is the final output of the HPA axis, the loop linking your hypothalamus, pituitary, and…

Creatine kinase (CK) is an enzyme that helps regenerate ATP energy, by moving a phosphate from phosphocreatine to ADP. It is busiest in tissues with high, fluctuating energy…

Creatinine is a waste product from your muscle's creatine. Your body makes it at a fairly steady rate, and your kidneys clear it (mostly by filtration, with a little tubular…

Cystatin C is a small protein (13 kDa) that inhibits certain enzymes (cysteine proteases). All your nucleated cells make it at a steady rate. Your kidneys' filters (glomeruli)…

D-dimer is a scrap left over when your body breaks down a blood clot. An enzyme called plasmin chops up stabilized fibrin, the clot's mesh. D-dimer is the debris. So it acts as a…

Dehydroepiandrosterone sulfate (DHEA-S) is the sulfated, long-lasting form of DHEA. Your adrenal cortex (the zona reticularis) secretes it. It is a precursor that your peripheral…

Estradiol (E2) is the most biologically active estrogen. Before menopause, it is made mainly in the ovaries. Smaller amounts come from converting androgens, a process called…

F2-isoprostanes are markers of oxidative stress in your body. They form when free radicals attack a fat (arachidonic acid) in your cell membranes, creating compounds that look…

Fasting glucose is your blood-sugar level after at least eight hours without eating. It reflects your baseline glucose balance. Several things set that balance. They are your…

Fasting insulin measures the insulin in your blood after an overnight fast. It reflects three things at once. First, your β-cells' output. Second, how much insulin your liver…

Ferritin is the protein your cells use to store iron, and a little of it leaks into your blood. That is why serum ferritin is the go-to blood test for your total iron stores. Low…

Fibrinogen (also called clotting factor I) is a large protein your liver makes that turns into fibrin, the mesh that forms a blood clot. It is also an 'acute-phase reactant',…

Free T3 (fT3) and free T4 (fT4) are the unbound, active fractions of two thyroid hormones, triiodothyronine and thyroxine. T4 is the main hormone your thyroid secretes. Your…

Free testosterone is the small slice of your testosterone that floats free in your blood. Most of it is bound to two proteins, SHBG and albumin. Only the 1 to 4% that is unbound…

Fructosamine means your glycated serum proteins, chiefly albumin, formed when glucose sticks on non-enzymatically and rearranges into a stable ketoamine (the Amadori product).…

Galectin-3 is a small protein (a lectin) released by your activated immune cells (macrophages). It pushes heart fibroblasts to multiply, lay down collagen, and remodel the heart…

GFAP (glial fibrillary acidic protein) is the main structural fiber inside mature astrocytes. (Astrocytes are a type of brain support cell.) It is a marker of 'reactive…

GGT (gamma-glutamyl transferase) is an enzyme anchored in cell membranes that helps recycle glutathione, your body's master antioxidant. It is most active in your liver, bile…

GlycA is a blood marker of long-term, low-grade inflammation. It is read by NMR (nuclear magnetic resonance) spectroscopy. The signal comes from sugar groups (N-acetyl methyl…

HDL (high-density lipoprotein) is the 'good' cholesterol carrier. It picks up cholesterol from your tissues and brings it back to your liver. That return trip is called 'reverse…

High-sensitivity troponin (hs-Tn) is a blood test for heart-muscle injury. It measures the cardiac proteins troponin I (hs-TnI) or troponin T (hs-TnT) in your blood, at levels…

Homocysteine is a sulfur-containing amino acid your body makes while processing methionine. It is cleared in two ways: remethylation or transsulfuration. Both depend on folate,…

hs-CRP (high-sensitivity C-reactive protein) is a blood marker of inflammation. Your liver makes CRP, mainly when prompted by the signal IL-6. The 'high-sensitivity' assay can…

Insulin-like growth factor 1 (IGF-1) is made mainly in your liver, under stimulation from growth hormone (GH). It carries out many of GH's anabolic effects on muscle, bone, and…

Interleukin-6 (IL-6) is a versatile cytokine. It is made by immune cells, fat cells, blood-vessel cells, and senescent cells. It signals two ways: through a membrane-bound…

Ionized calcium (iCa²⁺), also called free calcium, is the active part of your blood calcium. It makes up about 45 to 50% of the total. The rest is bound to albumin or tied up…

LDL (low-density lipoprotein) is the cholesterol carrier that drives heart disease. When you have too many ApoB-carrying LDL particles, they slip into your artery wall (the…

LDL-P (LDL particle number) counts how many LDL particles are in your blood, rather than how much cholesterol they carry. It is usually measured by NMR spectroscopy or…

Lp-PLA2 is an enzyme tied to vascular inflammation. (Its other name is platelet-activating factor acetylhydrolase.) It is made mainly by macrophages and lymphocytes, and in your…

Lipoprotein(a), or Lp(a), is an LDL-like particle. In it, apolipoprotein(a) is covalently linked to apoB-100 through a disulfide bond. Your plasma level is largely genetic (often…

The absolute lymphocyte count (ALC) is the total number of lymphocytes circulating in your blood. That includes your T cells, B cells, and NK cells. It comes from the…

Serum magnesium measures only the small slice of your body's magnesium that is in your blood. About 99% is locked away in bone, muscle, and soft tissue. So a blood test is a poor…

Multi-cancer early detection (MCED) tests are blood tests. They scan the cell-free DNA floating in your plasma. They look mainly at two things: methylation patterns and the…

Myeloperoxidase (MPO) is an enzyme stored in granules of your neutrophils and monocytes. During inflammation, it makes hypochlorous acid (essentially bleach) and other reactive…

The neutrophil-lymphocyte ratio (NLR) comes straight from a standard blood count. It is your neutrophil count divided by your lymphocyte count. A typical healthy range is about…

Neurofilament light chain (NfL) is a structural protein from inside large, myelinated nerve fibers. When nerve axons are injured, NfL leaks into the spinal fluid and blood.…

Non-HDL cholesterol (non-HDL-C) is simply your total cholesterol minus your HDL. It captures the cholesterol in all the 'bad', artery-clogging lipoproteins: LDL, VLDL, IDL,…

NT-proBNP (N-terminal pro-B-type natriuretic peptide) is the inactive piece snipped off proBNP when your heart-muscle cells are stretched, by high pressure in the ventricle wall…

The Omega-3 index is a blood test. It is the combined amount of two omega-3 fats, EPA and DHA, as a percentage of all the fatty acids in your red-blood-cell membranes. Because…

Oxidized LDL (oxLDL) is LDL that has been chemically altered by oxidation. Both its fats and its main protein (apolipoprotein B-100) get modified. This usually happens in your…

p-tau217 is the tau protein phosphorylated at threonine 217. It is the most Alzheimer-specific plasma biomarker available right now. Its levels rise early along the amyloid…

Serum phosphate measures the inorganic phosphate floating in your blood. Its level reflects a balance between what your gut absorbs, what your kidneys hold onto, and what moves…

Prostate-specific antigen (PSA) is an enzyme (a kallikrein-family serine protease) made almost only by prostate cells. Its normal job is to liquefy semen, but it leaks into your…

RDW (red cell distribution width) measures how much your red blood cells vary in size. Lab machines report it as a percentage, and the normal range is about 11.5 to 14.5%. A high…

Remnant cholesterol is the cholesterol packed inside triglyceride-rich lipoprotein remnants. When you are fasting, those are mainly VLDL and IDL; after meals, chylomicron…

Reverse T3 (3,3',5'-triiodothyronine) is the inactive twin of T3. (T3 is the thyroid hormone that drives your metabolism.) It forms when an enzyme called D3 (5-deiodinase type 3)…

SHBG (sex hormone-binding globulin) is a protein your liver makes that grabs and carries sex hormones in your blood. It binds about 44% of your testosterone and 30 to 60% of your…

Small dense LDL (sdLDL) is a smaller, denser subtype of LDL cholesterol particles (under about 25.5 nm across). They form mainly when you have high triglycerides and insulin…

Testosterone is the main androgen (male sex hormone). In men, it is made mostly by Leydig cells in the testes. In women, the ovaries and adrenals make smaller amounts. It…

Anti-TPO and anti-thyroglobulin (TgAb) are antibodies. Your immune system makes them against your own thyroid enzymes. They are the main blood markers of autoimmune thyroid…

Transferrin saturation (TSAT) is the share of iron-binding seats on transferrin, your blood's main iron-carrier, that are filled with iron. You calculate it as (serum iron ÷…

Triglycerides are the main way your body stores fat, from your diet and from what your body makes. They travel in your blood inside fat-carrying particles. The main ones are…

Thyroid-stimulating hormone (TSH) is released by your pituitary gland. It controls how much thyroid hormone you make, through negative feedback from the circulating thyroid…

The TyG index is a quick stand-in for insulin resistance. You calculate it as ln(fasting triglycerides [mg/dL] × fasting glucose [mg/dL] ÷ 2). Simental-Mendía et al. proposed it…

Uric acid is the end product of breaking down purines in your body. Your liver makes it (via an enzyme, xanthine oxidase), and you clear it mostly through your kidneys (~70%),…

The urine albumin-to-creatinine ratio (UACR) measures how much albumin is leaking into your urine, divided by your urinary creatinine (which corrects for how hydrated you are). A…

Vitamin B12 (cobalamin) and folate (vitamin B9) are essential helper molecules. They work in 'one-carbon metabolism'. B12 is needed for two enzymes. One is methionine synthase.…

25-hydroxyvitamin D (25-OH-D, or calcidiol) is the main circulating form of vitamin D, and the standard blood test for your vitamin D status. Your liver makes it by adding a…