Medical tests
Medical tests: what each measures, why it is ordered, how it is done, how results are read and what a test cannot tell you. Panels are broken down into their components, each linked to the biomarker it measures. Reference ranges belong to the laboratory that ran the test; guideline thresholds are quoted with their source and country. Written for education, not for interpreting an individual's results.
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Biopsy
Removal of a small piece of tissue or a few cells so a pathologist can examine them under the microscope. It is the only way to prove most cancers and many…
Blood glucose
The concentration of glucose in blood, measured from a vein or a fingerprick. Fasting, random and after-a-sugar-drink (oral glucose tolerance) versions answer…
Blood pressure measurement full
The pressure of blood against the artery walls, recorded as two numbers: the systolic pressure when the heart contracts and the diastolic pressure between…
BNP and NT-proBNP test full
A blood test for the natriuretic peptides the heart's ventricles release when they are stretched by high pressure or extra volume. It is the first test for…
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Cardiac stress test
The heart is made to work hard, by treadmill or bicycle exercise or by a drug that mimics exercise, while its electrical activity, images or blood flow are…
Creatinine and eGFR full
The everyday measure of how well the kidneys filter. Creatinine, a waste product of muscle, builds up in blood as filtration falls; the laboratory converts it,…
CRP test full
A blood test for C-reactive protein, a protein the liver releases within hours of significant inflammation, infection or tissue injury. It measures the size…
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Echocardiogram full
An ultrasound of the beating heart. It shows the size and thickness of the chambers, how strongly the ventricles pump, whether the valves open and close…
Electrocardiogram full
Ten sticky electrodes on the chest and limbs record the heart's electrical activity from twelve angles over ten seconds. The tracing shows rhythm, rate, the…
Electrolytes
The dissolved salts that set the water content of the body and the electrical behaviour of nerves, muscle and the heart: sodium, potassium, chloride,…
Endoscopy (as a test)
A flexible or rigid tube with a camera passed into a body cavity through a natural opening or a small cut, so the lining can be seen directly and sampled. Each…
ESR (erythrocyte sedimentation rate) full
An old but still useful test that measures how far red blood cells settle in a narrow tube in one hour. Inflammatory proteins such as fibrinogen and…
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Ferritin test full
A blood test that estimates the body's iron stores by measuring ferritin, the protein that holds iron inside cells. It is the best single test for iron…
Full blood count full
The most commonly ordered blood test: an automated count of the red cells, white cells and platelets in a small sample, with the size and haemoglobin content…
Full pulmonary function tests
Spirometry plus measurements it cannot make: the total volume of the lungs including the air that cannot be blown out, and how easily gas crosses from the air…
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HbA1c full
The fraction of haemoglobin that has glucose stuck to it. Because red cells live about 120 days, it reports the average blood glucose over the previous two to…
Hepatitis B tests full
A set of blood tests that shows whether someone has hepatitis B now, had it in the past, is immune from vaccination, or carries the virus long term. Each…
HIV test full
A blood test that looks for the human immunodeficiency virus, usually by detecting both a viral protein (p24 antigen) and the antibodies the immune system…
Hormone tests
Blood levels of hormones and related chemicals, interpreted against the time of day, the cycle and the level of the controlling hormone from the pituitary.…
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Lipid profile full
Measures the fats carried in blood: total cholesterol, LDL ('bad', deposited in artery walls), HDL ('good', carried away for disposal) and triglycerides. Used…
Liver function tests full
A panel of enzymes and proteins that together show whether liver cells are injured, whether bile is flowing, and whether the liver is still doing its…
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Pregnancy test
Detects human chorionic gonadotropin, a hormone made by the placenta from about a week after implantation. Urine tests give a yes/no answer; a blood test gives…
Prothrombin time and INR full
The prothrombin time measures how many seconds plasma takes to clot once the tissue-factor pathway is triggered; the INR expresses that time as a ratio…
Pulse oximetry and blood gases
A clip on the fingertip shines red and infrared light through the tissue and reads the colour of pulsing blood to estimate how saturated haemoglobin is with…
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Thyroid function tests full
TSH from the pituitary and the thyroid hormones T4 and T3 measured together. Because the pituitary reacts to tiny changes in hormone level, TSH is the most…
Troponin test full
A blood test for cardiac troponin, a protein released when heart muscle cells are injured. It is the test that rules a heart attack in or out: with modern…
TSH test full
The single most sensitive blood test of thyroid function: TSH from the pituitary rises when the thyroid is underactive and falls when it is overactive, often…
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Urinalysis full
A plastic strip with chemical pads dipped into a fresh urine sample. In sixty seconds it screens for infection, blood, protein, glucose, ketones and how…
Urine culture
A urine sample is spread on culture plates and incubated for 24-48 hours to grow any bacteria, identify them and test which antibiotics kill them. It turns a…
Urine protein
Healthy kidney filters hold back almost all protein. Measuring albumin leaking into urine, corrected for how dilute the sample is, detects kidney damage years…
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Vitamin B12 and folate full
Two blood tests, usually ordered together, for the vitamins the bone marrow needs to make normal red cells and the nervous system needs to keep nerves working.…
Vitamin D test full
Measures 25-hydroxyvitamin D, the storage form the liver makes from vitamin D obtained from sunlight on skin and from food or supplements. It is the best…