Whoop blood test: 43 biomarkers for athletes

SHBG stands for sex hormone binding globulin. It is a protein made by the liver. SHBG binds testosterone tightly and oestradiol somewhat more loosely. Hormone bound to SHBG cannot act in the tissues. SHBG therefore determines how much of your total testosterone is genuinely available. SHBG is not itself a sex hormone but a transport protein. Results are reported in nmol/l. Normal values differ by sex and by age, and in men SHBG rises as they get older. An SHBG should therefore be assessed alongside total testosterone, never on its own.

TSH is thyroid-stimulating hormone. The pituitary gland makes it, and uses it to drive your thyroid. At the laboratory that runs the test the usual adult range runs from 0.27 to 4.20 mE/L. A high TSH usually fits an underactive thyroid. A low value usually fits an overactive one. That direction feels inverted, and it is. TSH is the pituitary signal, not the thyroid hormone itself. Laboratories use slightly different limits from one another. Always read the reference value printed on your own result. And a single measurement is never a diagnosis.

Your ALT value shows how much alanine aminotransferase is in your blood. This enzyme sits mainly in the liver. That makes ALT the most liver-specific of the routine enzymes. When it reaches the blood, liver cells have been damaged. In adult men the reference range runs to 45 u/l, and in women to 34 u/l. A mildly raised result is common and has several causes. Fatty liver leads that list, well ahead of alcohol and hepatitis.

LDL cholesterol is the amount of cholesterol carried inside LDL particles, the particles that can build up in the artery wall. That is where its nickname comes from: the bad cholesterol. Two things rarely appear on a report. First, in a routine lipid panel LDL is usually not measured but calculated from your total cholesterol, your HDL and your triglycerides. Second, the 3.0 mmol/l upper limit is a population reference interval, not a target. What counts as a good LDL for you is decided by your overall cardiovascular risk, not by the line printed on the page.

Cortisol is the body's primary stress hormone, produced by the adrenal glands. It regulates metabolism, immune responses, and the sleep-wake cycle. Levels follow a natural daily rhythm, peaking in the morning and declining throughout the day.

DHEA-S (dehydroepiandrosterone sulfate) is the most abundant adrenal hormone and serves as a precursor to both oestrogen and testosterone. It declines naturally with age and reflects overall adrenal reserve.

Estradiol (E2) is the most potent form of estrogen, playing a key role in reproductive health, bone density, and cardiovascular function. Abnormal levels may indicate hormonal imbalances that your healthcare provider can help evaluate.

Free testosterone is the unbound, bioavailable form of testosterone that can directly enter cells and activate receptors. It may indicate your body's functional androgen activity. Your healthcare provider can help interpret what your levels mean.

Follicle-stimulating hormone (FSH) is produced by the pituitary gland and plays an essential role in reproductive function. It regulates egg development in women and sperm production in men. Abnormal levels may indicate changes in fertility or hormonal health.

An LH blood test measures luteinizing hormone, a pituitary hormone essential for reproductive function. LH plays a key role in triggering ovulation in women and stimulating testosterone production in men.

Total testosterone measures the combined amount of bound and free testosterone in the blood. As the primary androgen, testosterone may influence muscle mass, bone density, libido, mood, and energy levels in both men and women.

Bicarbonate is an electrolyte that helps maintain the body's acid-base balance. It acts as a buffer in the blood, neutralising excess acids and helping to keep your pH within a healthy range.

Calcium is the most abundant mineral in the body, essential for strong bones and teeth, muscle contraction, nerve signalling, and blood clotting. Most calcium is stored in bones and teeth, with a small amount circulating in the blood.

Chloride is an essential electrolyte that helps maintain fluid balance, blood pressure, and the body's acid-base equilibrium. It works closely with sodium and potassium to regulate these vital functions.

Ferritin is a protein that stores iron, so your ferritin level shows how large your iron reserve is. Serum iron only measures how much iron is circulating in your blood at that moment; ferritin describes the reserve behind it. That reserve empties before your haemoglobin falls, so a low ferritin can already cause symptoms while your blood count still looks normal. Ferritin also rises with inflammation, infection and liver strain, which is why it can only be read properly alongside a CRP. Commonly used reference values are 30 to 400 µg/l for men and 15 to 150 µg/l for women, but your own laboratory report is what counts.

Serum iron measures the amount of circulating iron in your blood. Iron is essential for haemoglobin production, oxygen transport, and energy metabolism throughout the body.

Magnesium is an essential mineral involved in over 300 enzymatic reactions in the body, including energy production, muscle and nerve function, blood sugar regulation, and bone development.

Potassium is an essential electrolyte and mineral that helps regulate heartbeat, muscle contractions, nerve signals, and fluid balance. It is one of the most important minerals for cardiovascular health.

Sodium is a vital electrolyte that regulates fluid balance, blood pressure, and nerve and muscle function. It is the primary cation in extracellular fluid and is closely regulated by the kidneys.

Transferrin is the main protein responsible for transporting iron in the blood. It carries iron from the gut and storage sites to cells that need it, including bone marrow for red blood cell production.

C-Reactive Protein (CRP) is a protein produced by the liver in response to inflammation. It is a general marker of inflammation and can rise rapidly during infections, injuries, or chronic inflammatory conditions.

Homocysteine is an amino acid produced during protein metabolism. Elevated levels may be associated with an increased risk of cardiovascular disease, cognitive decline, and other health conditions.

Fasting glucose measures the level of sugar (glucose) in your blood after an overnight fast. It is one of the primary tests used to screen for and monitor diabetes and pre-diabetes.

HbA1c (glycated haemoglobin) reflects your average blood sugar levels over the past 2-3 months. It is the gold standard for long-term blood sugar monitoring and diabetes management.

Apolipoprotein B (ApoB) is the main protein on LDL and other atherogenic lipoproteins. Each atherogenic particle carries exactly one ApoB molecule, making it a precise measure of the total number of particles that can contribute to plaque formation.

HDL cholesterol is the amount of cholesterol carried inside the HDL particles in your blood. Those particles pick cholesterol up from your tissues and from the artery wall and take it back to the liver. That transport is what earned HDL the nickname good cholesterol. The nickname is misleading. HDL is above all a mirror of your metabolism: the value drops with excess weight, insulin resistance, smoking and inactivity, and it is those factors that carry the risk. Drugs that raise HDL substantially do not reduce the number of cardiovascular events. And more is not always better: at very high values, mortality in large population studies turns back upwards. So never read your HDL on its own. It only takes on meaning alongside your triglycerides, your LDL and your overall risk profile.

Total cholesterol measures the combined amount of HDL, LDL, and VLDL cholesterol in your blood. It provides an overview of your lipid status but should be interpreted alongside individual components for a complete cardiovascular risk picture.

Albumin is the most abundant protein in the blood, produced by the liver. It maintains fluid balance, transports hormones and nutrients, and serves as an indicator of liver and kidney function.

HOMA-IR (Homeostatic Model Assessment for Insulin Resistance) is a calculated index derived from fasting glucose and fasting insulin levels. It is widely used to estimate insulin resistance, a condition where the body's cells respond less effectively to insulin.

Alkaline phosphatase, usually shortened to ALP on a report, is an enzyme found in almost every tissue. Two sources account for nearly all of what reaches the blood. The first is the liver, and within it mainly the cells lining the small bile ducts. The second is bone, where the enzyme is released as new bone tissue is built. A raised result therefore does not yet say where the rise came from. That question is not answered by this one number. It is answered by the values beside it, by your age and by your situation.

Your AST value shows how much aspartate aminotransferase is circulating in your blood. It is an enzyme that leaks out whenever cells are damaged. AST sits in the liver, but equally in skeletal muscle, heart muscle, kidneys, brain and red blood cells. That is why a raised AST is not, on its own, a liver value. A hard training session the day before explains the result more often than liver disease does. The reference range runs up to 35 u/l in men and 31 u/l in women. What the number means only becomes clear alongside ALT, gamma-GT and CK.

Total bilirubin measures the combined amount of direct and indirect bilirubin in your blood. Bilirubin is a waste product formed during the normal breakdown of red blood cells, and elevated levels may indicate liver disease, bile duct problems, or increased red blood cell destruction.

Total protein measures the combined amount of albumin and globulins in your blood. These proteins play essential roles in maintaining fluid balance, fighting infections, transporting substances, and supporting tissue repair.

BUN (blood urea nitrogen) measures the amount of urea nitrogen in your blood, a waste product formed when the body breaks down protein. It is primarily used to evaluate kidney function and can be influenced by diet, hydration status, and liver health.

Creatinine is a waste product generated by normal muscle metabolism that is filtered out of the blood by the kidneys. It is widely regarded as the gold standard marker for evaluating kidney function, as consistent production makes it a reliable indicator of filtration efficiency.

Vitamin D is a fat-soluble vitamin that plays a key role in calcium absorption, bone health, and immune function. It is primarily produced in the skin through sunlight exposure and can also be obtained from certain foods and supplements.

eGFR (estimated glomerular filtration rate) is a calculated measure of how effectively your kidneys filter waste from the blood. It is the gold standard for diagnosing and staging chronic kidney disease and is derived from blood creatinine or cystatin C levels along with demographic factors.

Fasting insulin measures the amount of insulin in your blood after an overnight fast. It helps assess how efficiently your body manages blood sugar and can reveal insulin resistance before glucose levels become abnormal.

A leukocyte differential test measures the relative proportions of different types of white blood cells in your blood. It provides a detailed breakdown of your immune cell populations, offering valuable insight into your immune system's function.

Transferrin saturation measures the percentage of the iron-transport protein transferrin that is occupied by iron. It is a key indicator of your body's iron status and helps distinguish between different causes of iron-related disorders.

Lp(a), in full lipoprotein(a), is an LDL-like particle with an extra protein bolted onto it: apolipoprotein(a). That single extra protein makes the particle more damaging to the artery wall than an ordinary LDL particle. What makes Lp(a) unusual is that its level is more than 90 percent written into your DNA. It is set by the LPA gene, fixed early in life, and barely changes afterwards. Diet, exercise and weight loss shift the value hardly at all. That is why European consensus recommends measuring Lp(a) at least once in the life of every adult. A single test usually suffices: you learn a number that will not change again.

Triglycerides are the most common type of fat in the body, used for energy storage. Elevated levels may be associated with increased risk of cardiovascular disease, especially when combined with other lipid abnormalities.

A basic blood count measures three core values in your blood: hemoglobin, white blood cells and platelets. Together they say something about oxygen transport, immune defence and clotting. It is a simple baseline check, without the red-cell indices and white-cell differential of a complete blood count.