Biomarker Guide

Total cholesterol is a measure of all the cholesterol-carrying particles in your blood, including LDL (bad), HDL (good), and VLDL fractions.

Triglycerides are the most common form of fat in the body, circulating in the bloodstream as a major energy source.

HDL (high-density lipoprotein) is often called 'good cholesterol' because it helps transport excess cholesterol from the arteries back to the liver for processing and removal — a process known as reverse cholesterol transport.

LDL (low-density lipoprotein) is the primary carrier of cholesterol to cells throughout the body.

VLDL (very low-density lipoprotein) is a type of lipoprotein produced by the liver to transport triglycerides to tissues throughout the body.

Non-HDL cholesterol represents all cholesterol-carrying particles that are NOT HDL — including LDL, VLDL, IDL, and lipoprotein(a).

The cholesterol/HDL ratio (also called the cardiac risk ratio) divides total cholesterol by HDL cholesterol.

The cholesterol-to-triglyceride ratio compares total cholesterol against triglyceride levels to provide insight into overall lipid balance.

Apolipoprotein B (ApoB) is a protein that forms the structural backbone of all atherogenic lipoprotein particles — LDL, VLDL, IDL, and Lp(a).

Apolipoprotein A-1 (ApoA1) is the main structural protein of HDL particles.

Lipoprotein(a) — or Lp(a) — is a modified form of LDL with an additional protein called apolipoprotein(a) attached.

LDL particle number (LDL-P) measures the actual count of LDL particles in the bloodstream rather than just the amount of cholesterol they carry.

Small dense LDL (sdLDL) refers to a subfraction of LDL particles that are smaller and denser than typical LDL.

Remnant cholesterol is the cholesterol carried by triglyceride-rich lipoprotein remnants — primarily IDL and chylomicron remnants — after they have delivered their triglyceride cargo.

Lp-PLA2 (lipoprotein-associated phospholipase A2) is an enzyme that travels bound to LDL particles in the bloodstream.

Apolipoprotein A-1 (ApoA-1) is the primary protein component of high-density lipoprotein (HDL) particles.

The ApoB/ApoA1 ratio compares the concentration of atherogenic lipoprotein particles (represented by ApoB) to cardioprotective HDL particles (represented by ApoA-1).

LDL particle size describes whether LDL cholesterol is carried in large, buoyant particles (Pattern A) or small, dense particles (Pattern B).

HDL particle number (HDL-P) measures the concentration of HDL particles in the blood, as distinct from the amount of cholesterol they carry (HDL-C).

Intermediate density lipoprotein (IDL) cholesterol represents lipoprotein particles in the metabolic transition between VLDL and LDL.

Fasting glucose is the concentration of glucose in the blood after an overnight fast of at least 8–12 hours.

HbA1c (glycated haemoglobin or glycosylated haemoglobin) measures what percentage of haemoglobin in red blood cells has had glucose attached to it.

Fasting insulin measures the level of insulin in the blood after an overnight fast.

HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) is a calculated index that estimates insulin resistance from simultaneous fasting glucose and fasting insulin measurements.

C-peptide is a small protein fragment produced in equal amounts to insulin during insulin synthesis.

Mean plasma glucose (or estimated average glucose, eAG) is a calculated measure that converts HbA1c into an estimated average blood glucose over 3 months, using the formula: eAG = (28.

Aspartate aminotransferase (AST), also known as SGOT (Serum Glutamic Oxaloacetic Transaminase), is an enzyme found mainly in the liver, heart muscle, and skeletal muscle.

Alanine aminotransferase (ALT), also called SGPT (Serum Glutamic Pyruvic Transaminase), is an enzyme found predominantly in the liver.

Alkaline phosphatase (ALP) is an enzyme found in several tissues throughout the body, with the highest concentrations in the liver, bone, kidneys, and intestines.

GGT (gamma-glutamyl transferase) is an enzyme found primarily in the liver and bile ducts, with smaller amounts in the kidneys and pancreas.

Bilirubin is a yellow pigment produced during the normal breakdown of red blood cells.

Direct bilirubin (also called conjugated bilirubin) is the water-soluble form that has been processed by the liver.

Indirect bilirubin is the unconjugated, fat-soluble form produced from haemoglobin breakdown before the liver processes it.

Albumin is the most abundant protein in the blood, produced exclusively by the liver.

Total protein measures all proteins in the blood, primarily albumin and globulins.

Globulins are a group of proteins in the blood that include immunoglobulins (antibodies), transport proteins, and clotting factors.

The A/G ratio (albumin to globulin ratio) is calculated by dividing serum albumin by serum globulin.

The albumin/globulin (A/G) ratio compares the two major protein fractions in the blood.

The A/G ratio (albumin-to-globulin ratio) is a calculated value from a comprehensive metabolic panel reflecting the balance between liver-produced albumin and immune-related globulin proteins.

Creatinine is a waste product generated from the breakdown of creatine phosphate in muscle.

eGFR (estimated glomerular filtration rate) measures how effectively the kidneys filter waste from the blood, expressed as the volume of blood filtered per minute per 1.

Urea is the main nitrogenous waste product of protein metabolism, produced in the liver and excreted by the kidneys.

Blood urea nitrogen (BUN) measures the amount of nitrogen in the blood in the form of urea.

Uric acid is the final breakdown product of purines — compounds found in many foods and produced during normal cell turnover.

The BUN-to-creatinine ratio compares blood urea nitrogen (BUN) with serum creatinine to help distinguish different types of kidney disease and azotaemia.

Cystatin C is a small protein produced at a constant rate by all nucleated cells and filtered freely by the kidneys.

Urine specific gravity measures the concentration of all solutes dissolved in urine relative to pure water.

Urine pH measures the acidity or alkalinity of urine on a scale of 0–14.

Urobilinogen is a colourless by-product of bilirubin metabolism.

TSH (thyroid stimulating hormone) is produced by the pituitary gland to regulate thyroid hormone production.

Free T4 (free thyroxine) measures the unbound, biologically active fraction of thyroxine — the main hormone produced by the thyroid gland.

Free T3 (free triiodothyronine) is the most biologically active thyroid hormone.

Anti-thyroglobulin antibodies (Anti-TG or TgAb) are autoantibodies directed against thyroglobulin, the protein precursor of thyroid hormones T3 and T4.

Anti-thyroid peroxidase antibodies (Anti-TPO or TPOAb) target the enzyme thyroid peroxidase, which catalyses the synthesis of thyroid hormones.

Reverse T3 (rT3) is a biologically inactive metabolite of thyroxine (T4), produced by an alternative deiodination pathway.

Total T3 (triiodothyronine) measures all T3 in blood — both protein-bound and free fractions.

Total T4 (thyroxine) measures all T4 in blood — bound to thyroid-binding globulin (TBG), albumin, and transthyretin, plus the small free fraction.

Haemoglobin is the iron-containing protein in red blood cells that carries oxygen from the lungs to tissues and returns carbon dioxide to the lungs.

The red blood cell (RBC) count measures the number of red blood cells (erythrocytes) per unit volume of blood.

Haematocrit (PCV or packed cell volume) is the percentage of blood volume occupied by red blood cells.

MCV (mean corpuscular volume) measures the average size of red blood cells.

MCH (mean corpuscular haemoglobin) is the average amount of haemoglobin per red blood cell.

MCHC (mean corpuscular haemoglobin concentration) measures the average concentration of haemoglobin within red blood cells.

RDW (red cell distribution width) measures the variation in the size of red blood cells.

The red blood cell (RBC) count measures the number of erythrocytes per unit volume of blood.

Red blood cell count expressed in millions per microlitre (M/mcL) is the standard CBC reporting format in many international labs.

Haemoglobin A2 (HbA2) is a minor adult haemoglobin variant composed of two alpha chains and two delta chains, normally comprising 1.

Haemoglobin F (HbF) is the primary haemoglobin in fetal life, with higher oxygen affinity than adult haemoglobin.

Haemoglobin S (HbS) is a variant haemoglobin caused by a point mutation in the beta-globin gene (glutamic acid → valine at position 6).

The total WBC (white blood cell) count, also called total leucocyte count (TLC) in Indian labs, measures all types of infection-fighting cells in the blood: neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

Neutrophils are the most abundant white blood cells and form the first line of defence against bacterial infections.

Lymphocytes are white blood cells that play a central role in adaptive immunity — B cells produce antibodies, T cells coordinate immune responses and kill infected or cancer cells, and NK cells destroy abnormal cells.

The total white blood cell (WBC) count, also called the total leukocyte count (TLC), measures all immune cells circulating in the blood.

WBC count expressed in thousands per microlitre (K/mcL) is the standard international reporting format for the complete blood count.

Neutrophils are the most abundant white blood cells, comprising 50–70% of the total WBC count in healthy adults.

Lymphocytes make up 20–40% of circulating white blood cells and are the key mediators of adaptive immunity.

Monocytes are large mononuclear white blood cells comprising 2–8% of the WBC count.

Eosinophils are granulocytic white blood cells normally comprising 1–4% of circulating WBCs.

Basophils are the rarest granulocytes, normally comprising less than 1% of circulating WBCs.

The absolute neutrophil count (ANC) is the actual number of neutrophils per mm³ of blood, calculated by multiplying total WBC by the neutrophil percentage.

The absolute lymphocyte count (ALC) is the total number of lymphocytes per mm³ of blood.

The absolute monocyte count (AMC) quantifies the actual number of monocytes in blood per mm³.

The absolute eosinophil count (AEC) is the actual number of eosinophils per mm³ of blood.

The absolute basophil count (ABC) measures the actual number of basophils per mm³ of blood.

Platelets (thrombocytes) are small cell fragments produced in the bone marrow that are essential for blood clotting.

Mean platelet volume (MPV) is a measure of the average size of platelets in the blood, expressed in femtolitres (fL).

C-reactive protein (CRP) is produced by the liver in response to inflammation, infection, or tissue injury.

ESR (erythrocyte sedimentation rate) measures how quickly red blood cells settle at the bottom of a test tube in one hour.

Homocysteine is an amino acid produced during the metabolism of methionine (found in animal proteins).

C-reactive protein (CRP) is an acute-phase reactant produced by the liver in response to inflammation, infection, or tissue injury.

Interleukin-6 (IL-6) is a multifunctional cytokine produced by immune cells, adipose tissue, and muscle.

Tumour necrosis factor-alpha (TNF-α) is a master pro-inflammatory cytokine produced primarily by macrophages and T cells.

Fecal calprotectin is a calcium-binding protein released from neutrophils during intestinal inflammation.

Ferritin is the body's primary iron storage protein, found mainly in the liver, spleen, and bone marrow.

Serum iron measures the amount of iron circulating in the blood bound to the transport protein transferrin.

TIBC (total iron binding capacity) measures the maximum amount of iron the blood can carry if transferrin (the iron transport protein) were fully saturated.

Transferrin saturation (TSAT) represents the percentage of transferrin that is bound to iron — calculated as serum iron divided by TIBC, multiplied by 100.

Unsaturated iron-binding capacity (UIBC) measures the remaining capacity of transferrin to bind additional iron — the fraction not yet occupied.

Sodium is the primary electrolyte in the blood and extracellular fluid, playing a critical role in fluid balance, nerve impulse transmission, and muscle contraction.

Potassium is the major intracellular electrolyte, essential for maintaining cell membrane potential, nerve signal transmission, muscle contraction (including the heart), and acid-base balance.

Calcium is the most abundant mineral in the body, essential for bone structure, muscle contraction, nerve transmission, blood clotting, and cell signalling.

Phosphorus is the second most abundant mineral in the body, found mainly in bones and teeth (85%) with the rest in cells and soft tissues.

Chloride is the major extracellular anion, working alongside sodium to regulate fluid balance, osmotic pressure, and electrical neutrality.

Total serum calcium measures all forms of calcium in blood: protein-bound (mainly to albumin), complexed to anions, and ionised (free).

Ionised calcium is the biologically active free fraction of serum calcium not bound to albumin or anions.

Vitamin D (25-hydroxyvitamin D or calcidiol) is the storage form of vitamin D measured in the blood.

Vitamin B12 (cobalamin) is an essential water-soluble vitamin involved in DNA synthesis, red blood cell formation, myelin sheath maintenance (protecting nerves), and one-carbon metabolism.

Folic acid (folate or vitamin B9) is a water-soluble B vitamin essential for DNA synthesis, cell division, amino acid metabolism, and the conversion of homocysteine to methionine.

Vitamin B6 (pyridoxine) is a water-soluble B vitamin involved in over 100 enzymatic reactions, including amino acid metabolism, neurotransmitter synthesis (serotonin, dopamine, GABA), haemoglobin production, and homocysteine metabolism.

Folate (vitamin B9) is an essential water-soluble B vitamin required for DNA synthesis, cell division, and red blood cell formation.

Methylmalonic acid (MMA) is a metabolite that accumulates when vitamin B12 is insufficient, as B12-dependent adenosylcobalamin is required for the conversion of methylmalonyl-CoA to succinyl-CoA.

Vitamin A (retinol) is a fat-soluble vitamin essential for vision (particularly night vision), immune function, cell growth and differentiation, and reproductive health.

Vitamin C (ascorbic acid) is an essential water-soluble antioxidant required for collagen synthesis, immune function, iron absorption, wound healing, and neurotransmitter production.

Vitamin E (alpha-tocopherol) is the principal fat-soluble antioxidant in human cell membranes, protecting polyunsaturated fatty acids from lipid peroxidation.

Total testosterone measures all testosterone in the blood — both free (biologically active) and bound to proteins (SHBG and albumin).

Free testosterone is the small fraction of testosterone not bound to sex hormone binding globulin (SHBG) or albumin, representing only 1–3% of total testosterone.

DHEA-S (dehydroepiandrosterone sulphate) is produced by the adrenal glands and serves as the precursor to both androgens (testosterone, DHT) and oestrogens.

Sex hormone binding globulin (SHBG) is a protein produced by the liver that binds tightly to testosterone and oestradiol, making them biologically inactive.

Total testosterone measures all testosterone in the blood — both bound (to SHBG and albumin) and free.

Dihydrotestosterone (DHT) is a potent androgen formed from testosterone by the enzyme 5-alpha reductase.

Estradiol (E2) is the most potent and biologically active form of oestrogen.

FSH (follicle stimulating hormone) is produced by the pituitary gland and stimulates follicle development in women's ovaries and sperm production in men's testes.

LH (luteinising hormone) is produced by the pituitary gland.

Prolactin is a hormone produced by the pituitary gland that stimulates breast milk production.

Estradiol (E2) is the most potent naturally occurring oestrogen and the dominant female sex hormone.

Progesterone is a steroid hormone produced primarily by the corpus luteum after ovulation, and by the placenta during pregnancy.

Cortisol is the primary stress hormone, produced by the adrenal glands in response to physical and psychological stress.

Morning cortisol (collected at 8 AM) captures the cortisol awakening response (CAR) — the peak of the daily diurnal cortisol rhythm.

Homovanillic acid (HVA) is the main terminal metabolite of dopamine.

Vanilmandelic acid (VMA) is the major urinary metabolite of the catecholamines norepinephrine (noradrenaline) and epinephrine (adrenaline).

5-Hydroxyindoleacetic acid (5-HIAA) is the primary urinary metabolite of serotonin (5-hydroxytryptamine).

IGF-1 (insulin-like growth factor 1) is produced mainly by the liver in response to growth hormone (GH) stimulation.

CPK (creatine phosphokinase, also called creatine kinase or CK) is an enzyme found primarily in skeletal muscle, heart muscle, and the brain.

Lactate dehydrogenase (LDH) is an enzyme found in virtually all body cells that converts pyruvate to lactate during anaerobic metabolism.

NT-proBNP (N-terminal pro-brain natriuretic peptide) is a cardiac biomarker released by the ventricular myocardium in response to increased wall stress, volume overload, or pressure overload.

High-sensitivity cardiac troponin T (hs-TnT) is the most sensitive and specific biomarker for myocardial injury.

Amylase is an enzyme produced by the pancreas and salivary glands that breaks down starches into sugars.

Lipase is an enzyme produced primarily by the pancreas that breaks down dietary fats (triglycerides) into fatty acids and glycerol.

Fecal pancreatic elastase-1 (PE-1) is a stable protease enzyme produced exclusively by pancreatic acinar cells that passes through the intestine largely unchanged.

Magnesium is the fourth most abundant mineral in the body and a cofactor for over 300 enzymatic reactions, including ATP energy production, DNA synthesis, protein synthesis, muscle and nerve function, and blood glucose regulation.

Zinc is an essential trace mineral involved in over 300 enzymatic functions, immune system development and function, wound healing, protein synthesis, DNA synthesis, cell division, smell and taste, and sexual hormone production.

Copper is an essential trace mineral required for iron metabolism, antioxidant defence (via superoxide dismutase), collagen synthesis, neurological function, and immune health.

Chromium is a trace mineral found in foods including broccoli, whole grains, nuts, and meats.

Manganese is an essential trace mineral required for the function of several key enzymes including manganese superoxide dismutase (MnSOD), arginase, and pyruvate carboxylase.

Molybdenum is an essential trace mineral that serves as a cofactor for several enzymes including xanthine oxidase, sulfite oxidase, and aldehyde oxidase, which are involved in the metabolism of sulphur-containing amino acids and purines.

Selenium is an essential trace mineral incorporated into selenoproteins including glutathione peroxidases (antioxidant enzymes), thioredoxin reductase, and iodothyronine deiodinases (required for T4-to-T3 thyroid hormone conversion).

Lithium is a trace element with emerging evidence of nutritional importance at low concentrations, distinct from the pharmacological doses used in psychiatry for bipolar disorder.

Strontium is an alkaline earth metal chemically similar to calcium.

Vanadium is a trace element found in small amounts in plants, animals, and soil.

The Omega-3 Index measures the percentage of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) in red blood cell membranes.

The AA/EPA ratio measures the balance between arachidonic acid (AA, an omega-6 fatty acid that promotes inflammation) and EPA (eicosapentaenoic acid, an omega-3 fatty acid that is anti-inflammatory).

The omega-6/omega-3 ratio reflects the balance of omega-6 and omega-3 polyunsaturated fatty acids in red blood cell membranes.

Total IgE (immunoglobulin E) is an antibody class produced by the immune system primarily in response to parasites and allergens.

Immunoglobulin E (IgE) is an antibody class produced by B cells in response to allergens and parasites.

Mercury is a toxic heavy metal with no beneficial role in the human body.

Lead is a highly toxic heavy metal with no safe level of exposure.

Arsenic is a toxic metalloid with both organic (naturally occurring in seafood, largely non-toxic) and inorganic (toxic) forms.

Serum barium measures exposure to barium, an alkaline earth metal found naturally in soil and water.

Cadmium is a toxic heavy metal classified as a Group 1 carcinogen by the IARC.

Nickel is a naturally occurring metal with widespread industrial use.

Aluminium is the most abundant metal in the Earth's crust and a common component of food, water, medications (antacids, phosphate binders), and cookware.

Platinum is a precious metal with emerging environmental and occupational exposure concerns.

PSA (prostate specific antigen) is a protein produced by both normal and cancerous prostate cells.

Prostate-specific antigen (PSA) is a serine protease enzyme produced almost exclusively by prostate epithelial cells.

Free PSA measures the fraction of prostate-specific antigen circulating unbound.

SARS-CoV-2 IgG antibodies are immunoglobulins produced by the immune system in response to COVID-19 infection or vaccination.

Eicosapentaenoic acid (EPA) is a long-chain omega-3 fatty acid found primarily in fatty fish, fish oil, and algae.

Docosahexaenoic acid (DHA) is a long-chain omega-3 fatty acid that is the structural backbone of cell membranes in the brain, retina, and testes.

Docosapentaenoic acid (DPA, n-3) is an intermediate omega-3 fatty acid in the pathway between EPA and DHA.

Alpha-linolenic acid (ALA) is the essential short-chain omega-3 fatty acid that must be obtained from diet.

Total omega-3 measures the combined percentage of all omega-3 fatty acids (EPA, DHA, DPA, ALA, and others) as a proportion of total fatty acids in red blood cell membranes or plasma.

Arachidonic acid (AA) is a long-chain omega-6 fatty acid found in animal foods including meat, eggs, and dairy.

Linoleic acid (LA) is the essential short-chain omega-6 fatty acid that must be obtained from diet.

Gamma-linolenic acid (GLA) is an omega-6 fatty acid formed from linoleic acid by the enzyme delta-6-desaturase.

Dihomo-gamma-linolenic acid (DGLA) is an omega-6 fatty acid metabolite formed from GLA.

Total omega-6 measures the combined percentage of all omega-6 fatty acids (LA, GLA, DGLA, AA, and others) in red blood cell membranes or plasma.

Oleic acid is the most abundant monounsaturated omega-9 fatty acid, making up the majority of olive oil (55-83%).

Nervonic acid is a very long-chain monounsaturated omega-9 fatty acid (C24:1n9) found predominantly in brain white matter sphingomyelin and in small amounts in dietary sources like salmon, mustard seed oil, and hemp oil.

Palmitic acid (C16:0) is the most common saturated fatty acid in the body and in most food sources including meat, dairy, and palm oil.

Stearic acid (C18:0) is a long-chain saturated fatty acid found in animal fats, chocolate (cocoa butter), and shea butter.

Myristic acid (C14:0) is a medium-long chain saturated fatty acid found in dairy products (butter, cheese, full-fat milk), coconut oil, and palm kernel oil.

Zonulin is a protein that regulates the permeability of tight junctions between intestinal epithelial cells, controlling what passes from the gut into the bloodstream.

Beta-glucuronidase is an enzyme produced by certain gut bacteria that breaks glucuronic acid bonds, deconjugating compounds that the liver has glucuronidated for excretion.

Short-chain fatty acids (SCFAs) are fermentation products produced by gut bacteria from dietary fibre.

Butyrate (n-butyrate) is the most important short-chain fatty acid for colon health, produced by bacterial fermentation of dietary fibre.