Blood tests explained

Understand your blood test results

Plain-English guides to the markers we measure in clinic: what each blood test checks, what high and low results can mean, and which 57 Health panel includes it. Written to inform, not to diagnose; your own results are always interpreted by a clinician.

Iron studies

Ferritin blood test

A ferritin blood test measures ferritin, the protein your body uses to store iron. It is the earliest and most sensitive marker of iron deficiency, usually falling before the iron in your blood or your haemoglobin does, so a low ferritin can flag depleted iron stores well before anaemia appears.

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TIBC blood test

A TIBC (total iron-binding capacity) blood test measures how much iron your blood could carry if it were fully loaded, essentially the spare capacity of transferrin, the protein that transports iron. It rises when iron is in short supply and falls when there's plenty, so it's a useful part of iron studies read alongside iron, ferritin and transferrin saturation.

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Iron blood test

A serum iron blood test measures the amount of iron circulating in your blood at the moment the sample is taken. On its own it swings with your recent meals and the time of day, so it's most useful as part of iron studies, read together with ferritin, transferrin and transferrin saturation.

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Transferrin saturation blood test

Transferrin saturation is the percentage of your blood's iron-transport capacity that is actually carrying iron. It's a central part of iron studies: a low saturation points towards iron deficiency, while a high saturation is one of the earliest signs of iron overload.

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Thyroid

TSH blood test

A TSH (thyroid-stimulating hormone) blood test measures the hormone your pituitary gland releases to tell your thyroid how much thyroid hormone to make. It is the most sensitive first-line check of thyroid function: a high TSH usually points to an underactive thyroid, and a low TSH to an overactive one.

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Thyroglobulin antibodies blood test

A thyroglobulin antibodies (anti-Tg) blood test looks for antibodies your immune system can make against your own thyroid. A positive result points to autoimmune thyroid disease, the most common underlying cause of an under- or over-active thyroid, and it's usually interpreted alongside anti-TPO antibodies and your thyroid function.

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Vitamins & minerals

Vitamin D blood test

A vitamin D blood test measures 25-hydroxyvitamin D (25-OH vitamin D), the stored form of vitamin D and the best indicator of your overall vitamin D status. It shows whether you have enough vitamin D for healthy bones, muscles and immune function, or whether you are insufficient or deficient.

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Vitamin B12 blood test

A vitamin B12 blood test measures the amount of B12 (cobalamin) in your blood, a vitamin your body needs to make healthy red blood cells and keep nerves and DNA working. A low B12 can cause tiredness, tingling and problems with memory or mood, and it is often checked alongside folate and iron.

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Folate blood test

A folate blood test measures folate (vitamin B9), a vitamin your body needs to make red blood cells and, in pregnancy, to support your baby's early development. It is usually measured alongside vitamin B12 because the two work together and their deficiencies can look alike.

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Magnesium blood test

A magnesium blood test measures a mineral your body needs for hundreds of processes, including muscle and nerve function, energy production and a steady heartbeat. A blood level is a useful check, though it doesn't always reflect your total body stores, so it's interpreted alongside your symptoms.

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Phosphate blood test

A phosphate blood test measures a mineral that works closely with calcium to build bones and teeth and to power your cells. Its level is controlled by the kidneys, parathyroid hormone and vitamin D, so an abnormal result often points towards one of these systems.

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Zinc blood test

A zinc blood test measures a mineral essential for immunity, wound healing, taste and smell, skin health and hormone function. A blood level is a reasonable guide, but zinc is affected by recent food and by any inflammation, so it's interpreted alongside your symptoms and diet.

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Inflammation

CRP blood test

A CRP (C-reactive protein) blood test measures a protein your liver releases when there is inflammation in the body. It rises within hours of infection, injury or a flare of an inflammatory condition and falls as things settle, which makes it a useful, general marker of how much inflammation is present, though not of its cause.

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Liver function

ALP blood test

An ALP (alkaline phosphatase) blood test measures an enzyme found mainly in your liver and bones, and it forms part of a standard liver function test. A raised ALP can point to the liver (especially the bile ducts) or to increased bone activity, so it is interpreted alongside other markers such as GGT to work out where it's coming from.

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GGT blood test

A GGT (gamma-glutamyl transferase) blood test measures a liver enzyme that is especially sensitive to the bile ducts, alcohol and certain medicines. It's part of a liver panel and is particularly useful for interpreting a raised ALP: a high GGT points to a liver rather than a bone cause.

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Globulin blood test

Globulins are a group of proteins in your blood that include antibodies and transport and clotting proteins. A globulin blood test (usually calculated as total protein minus albumin) gives a broad signal about your immune activity, inflammation and liver function, interpreted alongside albumin and total protein.

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Total protein blood test

A total protein blood test measures the combined amount of albumin and globulin, the two main groups of protein in your blood. It's a broad marker of nutrition, liver and kidney function and immune activity, and it's most informative when read alongside its albumin and globulin components.

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Kidney / U&E

Urea blood test

A urea blood test measures urea, a waste product made when your body breaks down protein and normally filtered out by your kidneys. It forms part of a kidney function panel (U&Es), but because urea is also affected by how hydrated you are and how much protein you eat, it's interpreted alongside creatinine and eGFR rather than on its own.

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Potassium blood test

A potassium blood test measures an electrolyte that keeps your nerves, muscles and heart working normally. It's part of the urea and electrolytes (U&E) panel, and because the body keeps potassium within a tight range, results outside it are taken seriously and interpreted alongside kidney function and your medicines.

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Creatinine & eGFR blood test

A creatinine blood test measures a waste product your muscles produce and your kidneys clear, and it is used to check how well your kidneys are working. From your creatinine, your age and your sex, the lab calculates your eGFR (estimated glomerular filtration rate), a score of kidney function out of roughly 100 that is usually the number people are given.

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Fertility & hormones

AMH blood test

An AMH (anti-Müllerian hormone) blood test gives an indication of your ovarian reserve, roughly how many eggs you have remaining. It's widely used when thinking about fertility or planning treatment such as IVF, but it reflects egg quantity rather than quality, so it's one part of a fuller picture rather than a yes-or-no fertility test.

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Prolactin blood test

A prolactin blood test measures a hormone made by the pituitary gland, best known for stimulating breast milk production. Outside pregnancy and breastfeeding, a high prolactin can disturb periods, fertility and libido, so it's often checked when investigating irregular cycles, unexplained infertility or hormone symptoms.

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Oestradiol blood test

An oestradiol (E2) blood test measures the main and most active form of oestrogen. In menstruating women it changes markedly across the cycle, so it's interpreted against the day it was taken; it's also used to assess menopause, fertility, and, in men, the balance with testosterone.

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Progesterone blood test

A progesterone blood test measures the hormone that rises after ovulation to prepare the womb lining for a possible pregnancy. Timed to the second half of the cycle (around day 21 of a 28-day cycle), it's the standard way to confirm that ovulation has taken place.

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Testosterone blood test

A testosterone blood test measures the main sex hormone in the blood, important for libido, energy, mood, muscle and bone in men, and relevant to women too. It is usually measured as total testosterone, with free testosterone and SHBG (the protein that binds testosterone) added to work out how much is actually active.

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Muscle

Creatine kinase blood test

A creatine kinase (CK) blood test measures an enzyme released when muscle is stressed or damaged. It rises after hard exercise, injury and certain medicines, and a markedly high level can signal significant muscle breakdown, which makes it useful for athletes, recovery monitoring and investigating muscle symptoms.

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Pancreas

Amylase blood test

An amylase blood test measures a digestive enzyme made mainly by the pancreas (and salivary glands) to break down carbohydrates. It's used chiefly to assess the pancreas: a markedly high amylase is a classic sign of pancreatitis, and it's often measured alongside the more pancreas-specific lipase.

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Lipase blood test

A lipase blood test measures a digestive enzyme made by the pancreas to break down fats. It's the more pancreas-specific of the two main pancreatic enzymes, so a raised lipase is a particularly useful sign of pancreatitis and is often measured alongside amylase.

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Diabetes & metabolic

Fasting insulin blood test

A fasting insulin blood test measures the hormone that moves sugar from your blood into your cells, taken after an overnight fast. Alongside fasting glucose it reveals insulin resistance, often years before blood sugar rises, which makes it a useful early marker of metabolic health.

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HbA1c blood test

An HbA1c blood test measures your average blood sugar over the past two to three months, by looking at how much glucose has attached to the haemoglobin in your red blood cells. It is the standard test used to diagnose and monitor type 2 diabetes, and unlike a fasting glucose test it does not need you to fast or depend on a single moment in time.

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Heart & lipids

Cholesterol blood test

A cholesterol blood test, or lipid profile, measures the fats in your blood that affect your heart and circulation: total cholesterol, LDL (the harmful kind), HDL (the protective kind) and triglycerides. Together they help estimate your risk of heart disease and stroke, which is why they are part of almost every general health check.

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Prostate

PSA blood test

A PSA blood test measures prostate-specific antigen, a protein made by the prostate gland, and it is used to help assess prostate health in men. On its own it cannot diagnose or rule out prostate cancer: PSA rises with age and with several harmless conditions, so a result is always interpreted with your age, symptoms and an examination.

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Ready to get tested?

Every marker here is measured in one of our in-clinic panels at 57 Rodney Street, Liverpool: a proper venous draw by a clinician, with results sent to you securely.

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