Biomarker Glossary

Biomarker Glossary

Biomarker Glossary

The Chxhealth Biomarker Glossary explains every biomarker on our blood test panels in plain English. Each guide covers what the biomarker measures, normal UK ranges, what high and low levels mean, symptoms to look for, and which Chxhealth panels test it. All samples are analysed by Randox, a UK laboratory accredited by UKAS, with plain English reports delivered in 3 to 5 working days.

Chxhealth is an information service. We do not diagnose, treat or prescribe. For medical advice about your results, please speak to a healthcare professional.

Metabolic and Diabetes

  • HbA1c. HbA1c is a UK blood test that measures your average blood sugar (glucose) level over the past 2 to 3 months. It is the standard marker used by the NHS to screen for, diagnose and monitor type 2 diabetes and prediabetes.
  • Glucose. Glucose is the main sugar in your blood and your body's primary energy source. A fasting blood glucose test measures your blood sugar after at least 8 hours without food and is one of the standard UK tests for diagnosing diabetes and prediabetes, alongside HbA1c.
  • Insulin. Insulin is the hormone that moves glucose from your bloodstream into your cells. A fasting insulin blood test is one of the best early markers of insulin resistance, the underlying driver of type 2 diabetes, PCOS and metabolic syndrome, often years before HbA1c or fasting glucose become abnormal.

Cardiovascular and Lipid

  • Cholesterol. Cholesterol is a fatty substance carried in your blood that your body uses to build cells and hormones. A cholesterol blood test measures total cholesterol, HDL (good cholesterol), LDL (bad cholesterol) and triglycerides, and is the standard UK test for assessing cardiovascular risk.
  • Triglycerides. Triglycerides are the most common type of fat in your blood. A triglycerides blood test measures the amount in mmol/L and is part of a standard UK lipid profile alongside cholesterol. High triglycerides raise your risk of heart disease, stroke and pancreatitis.

Iron and Haematology

  • Ferritin. Ferritin is a protein that stores iron in your body. A ferritin blood test is the best single marker of your iron stores and the most reliable way to detect iron deficiency, which is one of the most common nutritional deficiencies in the UK, especially in women.
  • Iron. Serum iron is the amount of iron circulating in your blood, bound to the transport protein transferrin. A serum iron test is interpreted alongside ferritin (iron stores), transferrin and transferrin saturation to give a full picture of iron status in the body.
  • Haemoglobin. Haemoglobin (Hb) is the iron containing protein in red blood cells that carries oxygen from the lungs to every tissue in your body. A haemoglobin blood test is the standard UK measure for anaemia and is a core component of any full blood count (FBC).

Liver

  • ALT. ALT (alanine aminotransferase) is a liver enzyme. A small amount circulates in the blood normally, but levels rise when liver cells are damaged. ALT is the most specific blood marker of liver injury and a standard test in any UK liver health, metabolic or general health screen.
  • AST. AST (aspartate aminotransferase) is an enzyme found in the liver, heart, muscles and other tissues. AST is tested alongside ALT to assess liver function. A raised AST often points to liver damage, particularly when interpreted with the AST to ALT ratio.
  • GGT. GGT (gamma glutamyl transferase) is a liver enzyme particularly sensitive to alcohol and bile duct problems. A GGT blood test is the most sensitive liver marker for alcohol related damage and is often the first liver enzyme to rise with even modest regular drinking.

Kidney

  • Creatinine. Creatinine is a waste product made by your muscles and filtered out by your kidneys. A creatinine blood test, combined with the calculated estimated glomerular filtration rate (eGFR), is the standard UK test for assessing kidney function and screening for chronic kidney disease.

Liver and Nutrition

  • Albumin. Albumin is the most abundant protein in your blood, made by the liver. It maintains fluid balance, carries hormones and medications, and is a key marker of liver function, nutritional status and overall health.

Thyroid

  • TSH. TSH (thyroid stimulating hormone) is the master regulator of your thyroid gland. A TSH blood test is the first line UK test for screening thyroid function, detecting underactive thyroid (hypothyroidism), overactive thyroid (hyperthyroidism), and monitoring thyroid medication.
  • Free T4. Free T4 (free thyroxine) is the unbound, active form of the main thyroid hormone circulating in your blood. A free T4 test is the next step after TSH to confirm or rule out hypothyroidism or hyperthyroidism, and is essential for monitoring levothyroxine therapy.
  • Free T3. Free T3 (free triiodothyronine) is the most biologically active thyroid hormone. While T4 is the main hormone your thyroid produces, T3 is the one that actually drives metabolism, energy and body temperature at the cellular level. Free T3 is essential for diagnosing T4 to T3 conversion problems and for fine tuning thyroid treatment.

Male and Female Hormones

  • Testosterone. Testosterone is the primary male sex hormone, also produced in smaller amounts in women. A testosterone blood test measures total and sometimes free testosterone, and is the standard UK test for investigating low libido, fatigue, muscle loss, infertility, mood changes and other symptoms of hormonal imbalance in both men and women.
  • SHBG. SHBG (sex hormone binding globulin) is a protein made by the liver that binds to testosterone and oestrogen and controls how much of each is biologically active in your body. SHBG is tested alongside total testosterone and oestradiol to assess free hormone levels, and changes with insulin resistance, thyroid function and liver health.
  • Oestradiol. Oestradiol (E2) is the main form of oestrogen in the body. In women it is produced mainly by the ovaries and regulates the menstrual cycle, bone health and many other functions. In men, smaller amounts are produced and play important roles in bone health and libido. An oestradiol blood test is essential for investigating fertility, menopause, hormonal symptoms and oestrogen excess in men.
  • Progesterone. Progesterone is a key female reproductive hormone produced mainly by the ovaries after ovulation. A progesterone blood test, classically taken on day 21 of the menstrual cycle, is the standard UK test for confirming ovulation, investigating fertility and assessing luteal phase function.

Adrenal and Stress

  • Cortisol. Cortisol is your main stress hormone, produced by the adrenal glands. It regulates blood sugar, blood pressure, inflammation and the sleep wake cycle. A cortisol blood test, ideally taken in the morning, is the standard UK screen for adrenal disorders and chronic stress.

Inflammation and Immunity

  • CRP. C-reactive protein (CRP) is a protein made by the liver in response to inflammation in your body. A CRP blood test is the most widely used UK marker of acute and chronic inflammation, used to investigate infection, autoimmune disease, cardiovascular risk and general inflammatory burden.

Fertility

  • AMH. AMH (Anti-Müllerian Hormone) is produced by the small developing follicles in the ovaries. An AMH blood test gives an estimate of ovarian reserve (the remaining egg supply) and is widely used in the UK for fertility planning, IVF assessment and investigating polycystic ovary syndrome (PCOS).

Nutritional

  • Vitamin D. Vitamin D is a fat soluble vitamin that supports bone health, immune function and mood. A vitamin D blood test measures the level of 25-hydroxy vitamin D, the main circulating form, in nmol/L. Deficiency is very common in the UK, particularly between October and April.
  • Vitamin B12. Vitamin B12 (cobalamin) is essential for red blood cell production, nerve function and DNA synthesis. A vitamin B12 blood test is the standard UK screen for B12 deficiency, a common cause of fatigue, anaemia and neurological symptoms, particularly in older adults, vegans and people with absorption problems.

Important. Chxhealth is a UK information service that provides biomarker blood test panels and educational content. We do not diagnose, treat or prescribe. The reference ranges and information on this glossary are general educational content and should not be used as a substitute for advice from a qualified healthcare professional.