Blood Test Glossary: What Each Marker Is

This glossary explains what each marker is, not what your results mean. We give you access to your data — not medical advice. No clinician reviews or comments on your results before they reach you. If you have questions about your own results, take your report to your GP; in an emergency call 111 or 999.

Your blood test report lists each marker by name, often with an abbreviation. This glossary gives a plain-English description of the markers measured across the Optimised Lifestyle blood tests, grouped by body system, with the panels that include each one. Markers marked “calculated” are worked out by the laboratory from other measurements rather than measured directly. For how a report is laid out, see how to read a blood test report; to convert between US and UK units, use the hormone unit converter.

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Sex hormones

Testosterone (total)

The main male sex hormone, made mainly in the testes in men and in smaller amounts by the ovaries and adrenal glands in women. “Total” testosterone counts all of it in the blood, whether bound to proteins or not.

Included in: Testosterone, Male Hormone, Female Hormone, Athlete Performance, Ultimate Men’s Health, Ultimate Longevity

Free testosterone

The small fraction of testosterone that is not bound to proteins in the blood. Labs usually calculate it from total testosterone, SHBG and albumin rather than measuring it directly.

Included in: Testosterone, Male Hormone, Female Hormone, Athlete Performance, Ultimate Longevity

SHBG (sex hormone binding globulin)

A protein made mainly in the liver that binds testosterone and oestradiol in the blood.

Included in: Testosterone, Male Hormone, Female Hormone, Athlete Performance, Ultimate Longevity

Free androgen index (FAI)

A calculated ratio of total testosterone to SHBG, used as an estimate of how much testosterone is available to tissues.

Included in: Testosterone, Male Hormone, Female Hormone, Athlete Performance, Ultimate Longevity

Albumin

The most abundant protein in blood plasma, made in the liver. It carries hormones, vitamins and other substances, and is used in the free testosterone calculation.

Included in: Testosterone, Male Hormone, Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

LH (luteinising hormone)

Released by the pituitary gland. It signals the testes to produce testosterone and, in women, the ovaries to release an egg.

Included in: Male Hormone, Female Hormone, Athlete Performance, Ultimate Women’s Health, Ultimate Longevity

FSH (follicle stimulating hormone)

Released by the pituitary gland. It supports sperm production in men and the development of egg follicles in women.

Included in: Male Hormone, Female Hormone, Athlete Performance, Ultimate Women’s Health, Ultimate Longevity

Oestradiol

The main form of oestrogen in the body, made mainly by the ovaries in women and in smaller amounts by other tissues in both sexes. In women it varies through the menstrual cycle.

Included in: Male Hormone, Female Hormone, Athlete Performance, Ultimate Women’s Health, Ultimate Longevity

Prolactin

A hormone made by the pituitary gland, best known for its role in milk production after childbirth. It is also present in men.

Included in: Male Hormone, Female Hormone, Athlete Performance, Ultimate Longevity

DHEA sulphate (DHEA-S)

The sulphated form of DHEA, an androgen precursor made mainly by the adrenal glands and the most abundant circulating adrenal hormone.

Included in: Male Hormone, Athlete Performance, Ultimate Longevity

Cortisol

The body’s main stress hormone, made by the adrenal glands. Levels follow a daily rhythm and are usually highest in the morning.

Included in: Athlete Performance, Ultimate Longevity

Thyroid

TSH (thyroid stimulating hormone)

Released by the pituitary gland. It tells the thyroid gland how much hormone to make.

Included in: Female Hormone, Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Thyroid Function, Ultimate Longevity

Free T4 (free thyroxine)

The unbound, available portion of thyroxine, the main hormone made by the thyroid gland.

Included in: Female Hormone, Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Thyroid Function, Ultimate Longevity

Free T3 (free triiodothyronine)

The unbound portion of triiodothyronine, the more active thyroid hormone. Much of it is made by converting T4 in other tissues.

Included in: Female Hormone, Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Thyroid Function, Ultimate Longevity

TPO antibodies

Thyroid peroxidase antibodies are immune proteins directed against an enzyme in the thyroid gland.

Included in: Thyroid Function, Ultimate Longevity

Thyroglobulin antibodies

Antibodies directed against thyroglobulin, a protein made by the thyroid gland.

Included in: Thyroid Function, Ultimate Longevity

Iron and red blood cells

Ferritin

A protein that stores iron inside cells. The amount in the blood reflects the body’s iron stores.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Thyroid Function, Iron & Ferritin, Ultimate Longevity

Iron (serum)

The amount of iron circulating in the blood at the time of the sample, which can vary during the day.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Iron & Ferritin, Ultimate Longevity

Transferrin

The main protein that carries iron around the body.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Iron & Ferritin, Ultimate Longevity

Total iron binding capacity (TIBC)

A calculated measure of how much iron the blood’s transport proteins could carry.

Included in: Iron & Ferritin

Haemoglobin (HGB)

The iron-containing protein in red blood cells that carries oxygen.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

Haematocrit (HCT)

The proportion of the blood volume made up of red blood cells.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

Red blood cell count (RBC)

The number of red blood cells in a given volume of blood.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

MCV (mean corpuscular volume)

The average size of red blood cells.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

MCH (mean corpuscular haemoglobin)

The average amount of haemoglobin in each red blood cell.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

MCHC (mean corpuscular haemoglobin concentration)

The average concentration of haemoglobin in a given volume of red blood cells.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

RDW (red cell distribution width)

A measure of how much red blood cells vary in size.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

White blood cells and platelets

White blood cell count (WBC)

The total number of white blood cells, which are part of the immune system.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

Neutrophils, lymphocytes, monocytes, eosinophils and basophils

The five main types of white blood cell, reported as a “differential” alongside the total count. Each has a different role in the immune system.

Included in: Athlete Performance, Ultimate Men’s Health (Clinic), Ultimate Women’s Health (Clinic), Ultimate Longevity

Platelets (PLT)

Small cell fragments involved in blood clotting.

Included in: Athlete Performance, Ultimate Men’s Health (Clinic), Ultimate Women’s Health (Clinic), Ultimate Longevity

MPV (mean platelet volume)

The average size of platelets.

Included in: Athlete Performance, Ultimate Men’s Health (Clinic), Ultimate Women’s Health (Clinic), Ultimate Longevity

IgA (immunoglobulin A)

An antibody found in the blood and on mucous surfaces such as the gut lining.

Included in: Ultimate Men’s Health, Ultimate Women’s Health

Cholesterol and fats

Total cholesterol

The combined cholesterol carried in all of the lipoprotein particles in the blood.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Cholesterol, Ultimate Longevity

HDL cholesterol

Cholesterol carried in high-density lipoprotein particles, which move cholesterol back toward the liver.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Cholesterol, Ultimate Longevity

LDL cholesterol

Cholesterol carried in low-density lipoprotein particles, the main carriers of cholesterol from the liver to tissues.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Cholesterol, Ultimate Longevity

Non-HDL cholesterol

A calculated figure: total cholesterol minus HDL cholesterol.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Cholesterol, Ultimate Longevity

Triglycerides

The main form of fat carried in the blood. Levels are affected by recent meals.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Cholesterol, Ultimate Longevity

Total cholesterol / HDL ratio

A calculated ratio of total cholesterol to HDL cholesterol.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Cholesterol, Ultimate Longevity

Apolipoprotein A1 (Apo A1)

The main protein component of HDL particles.

Included in: Ultimate Longevity

Apolipoprotein B (Apo B)

The main protein component of LDL and related particles, with one per particle.

Included in: Ultimate Longevity

Lipoprotein(a) (Lp(a))

An LDL-like particle whose level is largely set by genetics.

Included in: Ultimate Longevity

Homocysteine

An amino acid produced during normal protein metabolism. Its level in the blood is influenced by B vitamins.

Included in: Ultimate Longevity

Liver

ALT (alanine aminotransferase)

An enzyme found mainly in the liver.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

ALP (alkaline phosphatase)

An enzyme found in the liver and in bone, among other tissues.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

GGT (gamma-glutamyl transferase)

An enzyme found mainly in the liver and bile ducts.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

Bilirubin

A yellow pigment made when red blood cells are broken down and processed by the liver.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

Total protein

The combined amount of albumin and globulins in the blood.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

Globulin

A calculated figure: total protein minus albumin. It covers a group of proteins that includes antibodies.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

Kidneys, minerals and electrolytes

Creatinine

A waste product from normal muscle activity that the kidneys filter out of the blood.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

eGFR (estimated glomerular filtration rate)

Calculated from creatinine, age and sex to estimate how well the kidneys filter the blood.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

Urea

A waste product made when the body breaks down protein, filtered by the kidneys.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

Uric acid

A waste product from the breakdown of purines, which come from some foods and are made by the body.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

Sodium, potassium and chloride

Electrolytes: charged minerals that help control fluid balance and the function of nerves and muscles.

Included in: Ultimate Longevity

Calcium and corrected calcium

A mineral needed for bones, nerves and muscles. Corrected calcium adjusts the measured value for the albumin level.

Included in: Ultimate Longevity

Magnesium

A mineral involved in muscle, nerve and enzyme function.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Ultimate Longevity

Zinc

A trace mineral involved in immune function and many enzymes.

Included in: Ultimate Longevity

Vitamins, inflammation and blood sugar

Vitamin D

A fat-soluble vitamin made in the skin in sunlight and found in some foods. The blood test usually measures 25-hydroxyvitamin D.

Included in: Thyroid Function, Vitamin Deficiency, Ultimate Longevity

Vitamin B12 (total and active)

A vitamin needed for nerve function and for making red blood cells. “Total” B12 includes B12 bound to carrier proteins; “active” B12 is the portion cells can use.

Included in: Male Hormone, Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Thyroid Function, Vitamin Deficiency, Ultimate Longevity

Folate (vitamin B9)

A B vitamin needed for making DNA and red blood cells.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Thyroid Function, Vitamin Deficiency, Ultimate Longevity

HbA1c (glycated haemoglobin)

Reflects average blood sugar over roughly the previous two to three months.

Included in: Athlete Performance, Ultimate Longevity

CRP (C-reactive protein)

A protein made by the liver that rises in the blood when there is inflammation somewhere in the body.

Included in: Athlete Performance, Ultimate Men’s Health, Ultimate Women’s Health, Thyroid Function, Iron & Ferritin, Ultimate Longevity

Creatine kinase (CK)

An enzyme found mainly in muscle that enters the blood when muscle is worked hard or damaged.

Included in: Ultimate Longevity

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