Biomarker Reference Library

Plain-English explanations of 25 common blood test markers — what each one measures, what the normal range is, and what an abnormal result may mean. All written with clinical accuracy and reviewed alongside The Vesey's testing panels.

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This reference library is designed to help you understand your blood test results. Each marker page covers what it measures, the UK reference range, what high and low results may indicate, and which The Vesey panels include that marker. These pages are educational resources — they do not replace clinical advice. Every result issued by The Vesey is reviewed by a clinician before release.

Blood Health

Haemoglobin (Hb)

The oxygen-carrying protein in red blood cells. The primary marker for diagnosing anaemia and polycythaemia.

White Blood Cell Count (WBC)

Your immune cell count — raised by bacterial infection and inflammation; lowered by viral illness, autoimmune disease, and chemotherapy.

Tiny cells essential for blood clotting. Low platelets cause bruising and bleeding; high platelets may reflect infection, iron deficiency, or bone marrow conditions.

Thyroid

TSH (Thyroid-Stimulating Hormone)

The pituitary signal that controls thyroid hormone production. The single most sensitive first-line test for thyroid dysfunction.

Free T4 (Thyroxine)

The active circulating form of thyroid hormone. Interpreted alongside TSH to confirm hypo- or hyperthyroidism and monitor treatment.

Metabolic & Diabetes

HbA1c (Glycated Haemoglobin)

Reflects average blood sugar over 8–12 weeks. The gold-standard test for diagnosing and monitoring diabetes mellitus.

Glucose (Blood Sugar)

A snapshot of blood sugar at the time of the test. Fasting glucose is used to diagnose pre-diabetes and diabetes.

Liver

ALT (Alanine Aminotransferase)

A liver enzyme released when liver cells are damaged. The principal marker of hepatocellular injury from fatty liver, hepatitis, or alcohol.

GGT (Gamma-Glutamyl Transferase)

The most sensitive routine marker of alcohol-related liver damage and bile duct disease. Rises with regular drinking before other liver markers are affected.

The liver's most abundant protein product. A sensitive marker of liver synthetic function, nutritional status, and chronic disease.

Kidney

A muscle waste product filtered by the kidneys. Raised creatinine signals impaired kidney function and is used to calculate eGFR.

eGFR (Glomerular Filtration Rate)

Calculated from creatinine, age, and sex — the gold-standard measure of kidney filtering capacity used to stage chronic kidney disease.

Iron & Nutrition

The body's iron storage protein. The most sensitive test for iron deficiency — often falls before haemoglobin or symptoms appear.

Essential for nerve function and red blood cell production. Deficiency causes fatigue, neuropathy, and macrocytic anaemia — particularly common in vegans and older adults.

Folate (Folic Acid)

A B-vitamin essential for DNA synthesis and red blood cell production. Deficiency causes anaemia and, in pregnancy, neural tube defects.

Vitamin D (25-OH)

The sunshine vitamin — critical for bone health, immune function, and muscle strength. Deficiency is extremely common in the UK.

Calcium (Serum)

The most abundant mineral in the body. Governs muscle contraction, heart rhythm, and nerve signalling. Abnormal calcium is always clinically significant.

Cardiovascular

Cholesterol (Total, LDL & HDL)

LDL ("bad") deposits in artery walls; HDL ("good") removes it. Understanding the balance between fractions is the key to accurate heart disease risk assessment.

LDL Cholesterol

The primary target of cholesterol-lowering treatment. High LDL accelerates atherosclerosis and raises the risk of heart attack and stroke.

CRP (C-Reactive Protein)

An acute-phase inflammation marker. Raised in infection, autoimmune disease, and as a cardiovascular risk marker (hs-CRP).

Hormonal

The primary male sex hormone — critical for energy, libido, muscle mass, and mood. Low testosterone (hypogonadism) is increasingly recognised in both men and women.

AMH (Anti-Müllerian Hormone)

The most reliable blood test for ovarian reserve. Predicts fertility potential, IVF response, and risk of early menopause. High AMH may indicate PCOS.

The primary stress hormone produced by the adrenal glands. Morning cortisol assesses adrenal function and detects Addison's disease or Cushing's syndrome.

PSA (Prostate-Specific Antigen)

A protein produced by prostate cells. Used to screen for and monitor prostate cancer and benign prostate conditions. Recommended for men aged 40+ or with a family history.

Electrolytes

Potassium (Serum)

The electrolyte that keeps your heart in rhythm. Both high and low potassium can cause dangerous cardiac arrhythmias — a clinically critical routine marker.

Not sure which test you need?

Our Lifestyle Screen covers the most important markers across blood health, liver, kidneys, thyroid, diabetes, cholesterol, and nutritional status — all in a single visit. Or speak to us and we'll help you choose the right panel.

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