Blood test results explained

Can reflect dehydration, smoking, sleep apnoea, living at altitude, testosterone therapy, or — uncommonly — a marrow disorder such as polycythaemia.

Large cells (macrocytic) point to B12 or folate deficiency, alcohol, an underactive thyroid, some medicines, or liver disease.

Usually accompanies a raised MCV.

A wide spread suggests a mixed or evolving picture — for instance iron deficiency developing on top of normal cells.

Dehydration, smoking, polycythaemia.

Most often ordinary infection. Also steroids, physical stress, smoking, and — rarely — leukaemia, especially if very high or accompanied by abnormal cells.

Bacterial infection, inflammation, tissue injury, steroids, physical or emotional stress, smoking.

Viral infections (glandular fever classically), whooping cough, and — if persistently high in an older adult — chronic lymphocytic leukaemia.

Chronic infection, recovery from infection, inflammatory bowel disease, some marrow disorders.

Allergy, asthma, eczema, drug reactions, parasites, and — uncommonly — vasculitis or a marrow disorder.

Rarely, chronic myeloid leukaemia; also allergy and inflammation.

Very often a reaction to inflammation, infection, iron deficiency, or recent surgery. If persistently high without a cause, a marrow disorder is considered.

Larger, younger platelets — the marrow is replacing them quickly.

Reduced kidney function, dehydration, some medicines. It also runs higher in muscular people and after heavy exercise or a large meat meal — without any kidney problem at all.

Dehydration, a high-protein diet, bleeding into the gut, steroids, and reduced kidney function.

Usually reflects water loss rather than too much salt — dehydration, or rarely diabetes insipidus.

Kidney impairment, ACE inhibitors, ARBs, spironolactone, potassium supplements — and very commonly a false result from red cells breaking in the tube (haemolysis) or a tight tourniquet.

Fluid loss, and some acid-base disturbances.

Vomiting, some diuretics.

Fatty liver (by far the commonest cause in the UK), alcohol, viral hepatitis, medicines including some statins, and autoimmune liver disease.

Liver injury, but also muscle injury and hard exercise.

Blocked or inflamed bile ducts, gallstones, some drugs — and also bone conditions, growth in adolescents, and normal pregnancy (from the placenta).

Alcohol, fatty liver, bile duct disease, and several common medicines.

Gilbert's syndrome (a harmless inherited variant present in around 1 in 20 people, in which bilirubin rises with fasting or illness), gallstones, hepatitis, and haemolysis.

Dehydration.

Chronic infection, autoimmune disease, and myeloma.

Overactive parathyroid glands are the commonest cause in someone who feels well. Cancer is the commonest cause in someone who is unwell. Also excess vitamin D, and some diuretics.

Kidney impairment, underactive parathyroids.

Kidney impairment, or magnesium-containing laxatives and antacids.

Almost always from supplements. Very high levels can raise calcium and harm the kidneys.

A raised PTH with a raised calcium indicates primary hyperparathyroidism. A raised PTH with a low or normal calcium is usually the body responding correctly to vitamin D deficiency or kidney disease.

Gout, kidney impairment, diuretics, alcohol, and a diet heavy in red meat, shellfish or fructose.

Diet, genetics, an underactive thyroid, kidney and liver disease.

Genetics (including familial hypercholesterolaemia), diet high in saturated fat, an underactive thyroid.

Exercise, moderate alcohol, and genetics.

Carries the same implications as a raised LDL.

Alcohol, sugar and refined carbohydrate, obesity, poorly controlled diabetes, an underactive thyroid, and some drugs.

A higher ratio indicates higher cardiovascular risk.

A raised ApoB means many small dense particles, and higher risk than the LDL alone suggests.

A raised level is a genetic risk factor. Diet and exercise barely change it; the response is to treat every other risk factor harder.

Raised levels indicate prediabetes or diabetes, depending on the degree.

Prediabetes or diabetes; also steroids, and acute illness.

Insulin resistance — the pancreas working hard to keep glucose normal.

A high TSH means the thyroid is underactive (hypothyroid): tiredness, weight gain, cold intolerance, constipation, low mood.

Overactive thyroid.

Can be raised in overactivity when T4 is still normal.

Positive TPO antibodies indicate autoimmune thyroiditis (Hashimoto's) — they predict progression to an underactive thyroid over time.

Iron overload (haemochromatosis) — but far more often, inflammation, infection, liver disease, alcohol or obesity, because ferritin is also an inflammatory protein.

Iron overload, or a recent iron tablet or meal.

Iron deficiency.

A persistently high saturation is the key screening finding in haemochromatosis.

Usually from supplements, and not harmful. Occasionally liver or blood disorders.

Supplements. Not harmful.

Almost always from over-supplementation.

Infection, inflammation, injury, and cancer. Very high levels suggest bacterial infection.

Chronically raised low-level inflammation is associated with higher cardiovascular risk.

Inflammation, infection, anaemia, myeloma, and rising age. It also runs higher in women.

Inflammation, and raised protein levels.

Hard exercise (the commonest cause by far — a gym session can raise it several-fold for days), statins, injury, viral illness, inherited muscle disease, and rarely an underactive thyroid.

Heart attack, but also heart failure, arrhythmia, pulmonary embolism, kidney impairment, sepsis and myocarditis.

Heart failure, but also atrial fibrillation, kidney impairment and rising age.

Pancreatitis; amylase also rises with salivary gland problems and some abdominal emergencies.

A positive result makes coeliac disease likely and leads to a gastroscopy with biopsy to confirm it.

Inflammatory bowel disease — Crohn's or ulcerative colitis. Also NSAIDs and infection.

A raised FSH suggests the ovaries are responding less — the pattern seen around and after the menopause.

A raised LH relative to FSH is a recognised pattern in polycystic ovary syndrome.

Varies hugely across the cycle; also raised on some HRT.

Confirms ovulation.

Pregnancy, breastfeeding, stress, nipple stimulation, many antipsychotics and antidepressants, an underactive thyroid — and a benign pituitary tumour (prolactinoma).

Raised free testosterone, often with a low SHBG, is the classic biochemical pattern of PCOS. A markedly raised level needs prompt investigation for a hormone-producing tumour.

Often raised in PCOS.

Supplementation, and rarely a tumour.

SHBG rises with age, an overactive thyroid and liver disease.

Raised FSH/LH with low testosterone means the testes are failing (primary).

Prostate cancer — but also benign enlargement (much commoner), infection, a recent digital examination, cycling, and ejaculation within 48 hours.

A positive ANA is found in lupus, Sjögren's, scleroderma and myositis — but also in around 1 in 10 entirely healthy people, more often with rising age.

Each antibody points towards a particular condition — Ro and La towards Sjögren's, Scl-70 towards scleroderma, Jo-1 towards myositis.

Rheumatoid arthritis, but also hepatitis C, Sjögren's, chronic infection, and healthy older people.

Strongly suggests rheumatoid arthritis, and predicts a more erosive course.

Raised anti-dsDNA suggests active lupus, particularly with kidney involvement.

Warfarin, liver disease, vitamin K deficiency. A raised INR means a greater tendency to bleed.

Haemophilia, von Willebrand disease, heparin, and lupus anticoagulant.

Inflammation and pregnancy.

A clot — but also infection, inflammation, surgery, pregnancy, cancer and rising age.

A positive surface antigen means current hepatitis B infection and needs specialist care.

A positive antibody with detectable RNA means active infection.

A reactive result is always confirmed on a second sample before anything is said with certainty.

A reactive result needs confirmatory testing — the antibodies persist for life after treatment.

A positive result means infection and requires treatment, and partner notification.

Positive IgG means you are immune.

A single raised class with a paraprotein suggests myeloma; a general rise suggests chronic infection or liver disease.

Allergy, eczema, asthma and parasitic infection.

A positive result means you are *sensitised* — your immune system recognises it.

Ovarian cancer — but also endometriosis, fibroids, menstruation, pregnancy, liver disease and any inflammation of the abdominal lining.

Bowel cancer, but also smoking, inflammatory bowel disease and liver disease.

Pancreatic cancer, but also gallstones, bile duct obstruction and pancreatitis.

Raised in certain testicular tumours and in liver cancer; hCG also rises in normal pregnancy.

Cushing's syndrome, steroid treatment, and acute stress or illness.

B12 or folate deficiency, kidney impairment, and the MTHFR gene variants.

A paraprotein may indicate myeloma, or the much commoner and usually harmless MGUS, which is simply monitored.