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Biomarker encyclopaedia
Plain-language guides for everyday health and training context: what common UK blood markers mean, how they relate to the body, and when athletes pay attention. Educational only, not a diagnosis or medical advice.
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Haematology
- Basophils x10⁹/L Rare white cells involved in allergic and inflammatory responses.
- Basophils % % Basophils as a percentage of all white cells.
- Eosinophils x10⁹/L White cells linked to allergy, parasites, and some inflammatory diseases.
- Eosinophils % % Eosinophils as a percentage of all white cells.
- Fibrinogen g/L A clotting protein that also rises with inflammation.
- Haematocrit L/L Haematocrit (packed cell volume), the fraction of blood that is red cells.
- Haemoglobin g/L The oxygen-carrying protein in red blood cells; central to energy, breathlessness, and anaemia assessment.
- Lymphocytes x10⁹/L White cells for viral defence and immune memory (T and B cells).
- Lymphocytes % % Lymphocytes as a percentage of all white cells.
- Mean corpuscular haemoglobin pg Mean corpuscular haemoglobin: average haemoglobin per red cell.
- Mean corpuscular haemoglobin concentration g/L Mean corpuscular haemoglobin concentration: haemoglobin concentration within red cells.
- Mean corpuscular volume fL Mean corpuscular volume: average red-cell size; helps classify anaemia patterns.
- Mean platelet volume fL Average platelet size; a companion FBC index often reported on venous samples.
- Monocytes x10⁹/L White cells that clear debris and help coordinate immune responses.
- Monocytes % % Monocytes as a percentage of all white cells.
- Neutrophils x10⁹/L The most abundant white cells; first responders to bacterial infection.
- Neutrophils % % Neutrophils as a percentage of all white cells.
- Platelet distribution width fL How much platelet size varies; read alongside the platelet count and MPV.
- Platelets x10⁹/L Cell fragments that plug injured vessels; abnormal counts affect bleeding or clotting tendency.
- Red cell count x10¹²/L Number of red blood cells circulating in blood.
- Red cell distribution width % Red cell distribution width: variation in red-cell size.
- White cell count x10⁹/L Counts white blood cells that defend against infection and respond to inflammation.
Inflammation
- C-reactive protein mg/L C-reactive protein, a fast-rising blood marker of inflammation or infection.
- Erythrocyte sedimentation rate mm/hr How quickly red cells settle in a tube, a slow general marker of inflammation.
- Interleukin-6 pg/mL A signalling protein of the immune system, raised in inflammation.
Liver function
- Alanine aminotransferase U/L Alanine aminotransferase, a liver enzyme that rises when hepatocytes are stressed.
- Albumin g/L Main blood protein from the liver; reflects nutrition, inflammation, and fluid balance.
- Alkaline phosphatase U/L Alkaline phosphatase: enzyme from liver and bone; rises with bile-flow or bone turnover change.
- Amylase U/L A digestive enzyme from the pancreas and salivary glands.
- Aspartate aminotransferase U/L Aspartate aminotransferase: liver and muscle enzyme used with ALT for injury patterns.
- Bilirubin (total) µmol/L Yellow pigment from red-cell breakdown; high levels can cause jaundice.
- Gamma-glutamyl transferase U/L Gamma-glutamyl transferase: liver enzyme sensitive to alcohol, drugs, and bile-duct stress.
- Globulin g/L Usually calculated as total protein minus albumin; reflects antibody and other globulin proteins.
- Lipase U/L A pancreatic enzyme that digests fat; the preferred marker for pancreas inflammation.
- Total protein g/L Combined albumin and globulin proteins in serum.
Kidney function
- Creatinine µmol/L Muscle metabolism waste cleared by the kidneys; basis for eGFR.
- eGFR mL/min/1.73m² Estimated glomerular filtration rate: calculated kidney function from creatinine and demographics.
- Urea mmol/L Waste from protein metabolism; rises with reduced kidney filtration or dehydration.
- Uric acid µmol/L Purine breakdown product; high levels associate with gout risk.
Electrolytes & minerals
- Adjusted calcium mmol/L Albumin-adjusted (corrected) calcium: better reflects free calcium when albumin is abnormal.
- Bicarbonate mmol/L Bicarbonate / total CO₂: reflects acid–base balance in blood.
- Calcium (total) mmol/L Blood calcium: tightly regulated by parathyroid hormone, vitamin D, and the kidneys.
- Chloride mmol/L Electrolyte that moves with sodium and acid–base status.
- Magnesium mmol/L Mineral for muscle, nerve, and heart rhythm function.
- Phosphate mmol/L Mineral for bone, energy (ATP), and cell membranes.
- Potassium mmol/L Key electrolyte for heart rhythm and muscle contraction.
- Sodium mmol/L Main extracellular electrolyte controlling water balance and nerve/muscle excitability.
- Zinc µmol/L An essential mineral for immunity, wound healing, taste, and enzyme function.
Diabetes & metabolism
- C-peptide pmol/L A by-product of the body's own insulin production.
- Glucose (fasting) mmol/L Blood glucose after fasting: used in diabetes and prediabetes assessment.
- Haemoglobin A1c mmol/mol Average blood glucose over roughly 2–3 months; key diabetes monitoring test.
- Insulin pmol/L The hormone that moves glucose from blood into cells.
Lipids
- Apolipoprotein A1 g/L The main protein on HDL particles; part of advanced cholesterol profiling.
- Apolipoprotein B g/L The main protein on atherogenic lipoproteins; reflects particle number.
- Cholesterol (total) mmol/L Overall blood cholesterol, one input to cardiovascular risk, not a sole verdict.
- HDL % of total cholesterol % HDL cholesterol expressed as a share of total cholesterol.
- HDL cholesterol mmol/L HDL (“good”) cholesterol: particles that help reverse-transport cholesterol.
- LDL cholesterol mmol/L LDL (“bad”) cholesterol, most strongly linked to atherosclerotic risk.
- Lipoprotein (a) nmol/L A genetically influenced lipoprotein linked to cardiovascular risk; units vary by assay.
- Non-HDL cholesterol mmol/L Total cholesterol minus HDL: captures atherogenic lipoproteins including LDL.
- Total cholesterol/HDL ratio ratio Total cholesterol divided by HDL cholesterol, a simple lipid risk ratio.
- Triglycerides mmol/L Blood fats that rise after meals; very high levels raise pancreatitis risk.
Hormones & endocrine
- Adrenocorticotropic hormone pmol/L The pituitary hormone that tells the adrenal glands to make cortisol.
- Anti-Müllerian hormone pmol/L Anti-Müllerian hormone, an ovarian reserve marker that falls with age.
- Cortisol (morning) nmol/L Morning cortisol: adrenal steroid with a strong daily rhythm.
- DHEA sulphate µmol/L An adrenal androgen precursor that declines with age.
- Free androgen index % A calculated index of androgen activity from total testosterone and SHBG.
- Free T3 pmol/L Free triiodothyronine (FT3): mainly useful when hyperthyroidism is suspected.
- Free T4 pmol/L Free thyroxine (FT4): active T4 hormone paired with TSH to classify thyroid status.
- Free testosterone pmol/L The unbound (or loosely bound) testosterone fraction, often calculated from total testosterone and SHBG.
- Free testosterone to cortisol ratio ratio A calculated wellness ratio pairing free testosterone with cortisol.
- FSH IU/L Follicle-stimulating hormone: regulates ovarian follicles and testicular Sertoli cells.
- HCG IU/L Human chorionic gonadotrophin: best known as a pregnancy hormone.
- IGF-1 nmol/L The stable downstream marker of growth hormone activity.
- LH IU/L Luteinising hormone: triggers ovulation and supports sex-hormone production.
- Oestradiol pmol/L Main oestrogen in pre-menopausal women; low-level measurable in men.
- Progesterone nmol/L Hormone that rises after ovulation: used to confirm ovulation in cycle tracking.
- Prolactin mU/L Hormone for lactation; rises with stress, medicines, and pituitary disorders.
- SHBG nmol/L Sex hormone-binding globulin: protein that binds testosterone and oestradiol.
- Testosterone to free testosterone ratio ratio A calculated relationship between total and free testosterone.
- Thyroglobulin antibodies IU/mL Antibodies against thyroglobulin; used when assessing autoimmune thyroid disease.
- Thyroid peroxidase antibodies IU/mL Antibodies against thyroid peroxidase (TPO); the common autoimmune thyroid marker.
- Total testosterone nmol/L Primary male sex hormone (also measured on some women’s panels); linked to libido, muscle, mood, and cycle health.
- Total thyroxine (T4) nmol/L All thyroxine in the blood, bound and free together.
- TSH mIU/L Thyroid-stimulating hormone: first-line thyroid screening test from the pituitary.
Vitamins
- Active vitamin B12 pmol/L Holotranscobalamin, the metabolically available fraction of vitamin B12.
- Folate µg/L B-vitamin for DNA synthesis and healthy red cells; critical pre-pregnancy.
- Vitamin B12 ng/L Essential for nerves and red-cell production; deficiency causes anaemia and neurological symptoms.
- Vitamin D nmol/L 25-hydroxy vitamin D: status marker for bone, muscle, and immune context.
Iron studies
- Ferritin µg/L Iron storage protein and the usual first blood test for iron stores: highly relevant to fatigue and athletic performance.
- Iron µmol/L Circulating serum iron: fluctuates through the day and with meals.
- Total iron binding capacity µmol/L Total iron-binding capacity: how much iron blood proteins can carry; often calculated.
- Transferrin g/L The main iron-transport protein in blood; part of iron-status panels with ferritin and iron.
- Transferrin saturation % The percentage of the blood's iron carrier that is actually loaded with iron.
- Unsaturated iron binding capacity umol/L The spare iron-carrying capacity of the blood.
Tumour markers
Muscle enzymes
- Creatine kinase U/L Creatine kinase (CK), a muscle enzyme that rises after hard training, injury, or muscle disease.
- Lactate dehydrogenase U/L An enzyme released when cells of many kinds are damaged or turning over quickly.
- Myoglobin µg/L An oxygen-carrying protein in muscle, released when muscle is damaged.
Immune proteins
Heart health
- Homocysteine µmol/L A sulphur amino acid linked to B-vitamin status; samples need prompt processing.
- Troponin I (high sensitivity) ng/L A heart muscle protein; the standard blood test for heart muscle injury.
- Troponin T (high sensitivity) ng/L A heart muscle protein; the other standard assay for heart muscle injury.