Every test, explained.

Apolipoprotein B, written as apoB on your results, is the structural protein sitting on every LDL, VLDL and Lp(a) particle, so that one measurement counts those particles rather than the cholesterol they carry. ApoB counts the particles that carry cholesterol into the artery wall and is therefore sharper than LDL with belly fat, insulin resistance and high triglycerides.

HDL cholesterol, written as HDL-C on your results and known as the 'good' cholesterol, is the cholesterol carried back to the liver inside HDL particles. Read HDL beside LDL, triglycerides and non-HDL; in the risk estimate it counts through non-HDL, your total cholesterol minus your HDL.

LDL cholesterol, written as LDL-C on your results and known as the 'bad' cholesterol, is the cholesterol carried through your blood inside LDL particles that can build up in the artery wall. Read LDL beside non-HDL, HDL and triglycerides and as a trend; a markedly high value from a young age can be inherited, and then lifestyle is the foundation and medication usually joins it.

The LDL/HDL ratio divides the cholesterol that enters your vessel wall by the cholesterol that leaves it again, and so sums up two sides of your lipid profile in one number. Lower is better, but the ratio does not say which of the two moved, and that is why you always read it beside LDL and HDL themselves.

The triglycerides/HDL ratio divides your triglycerides by your HDL, two numbers that move in opposite directions with belly fat and insulin resistance. The ratio is therefore a quick measure of the lipid pattern that goes with a deranged sugar metabolism, and it falls with losing weight, exercise and less sugar.

Total cholesterol, written as TC on your results, is the sum of all the cholesterol in your blood: the LDL fraction, the HDL fraction and the cholesterol in the other lipoproteins. Read the total through its parts: LDL and non-HDL for your arteries, HDL and triglycerides for the pattern; the risk estimate uses total minus HDL.

Triglycerides, written as TG on your results, are the fats in which your blood carries energy and your body stores it; they respond strongly to what you eat, to alcohol and to your metabolism. Read them beside HDL and LDL, and note whether you were fasting, because they run higher after a meal.

Non-HDL cholesterol is your total cholesterol minus your HDL: all the cholesterol carried by particles with an apoB protein on them, and those are the particles that build up in the artery wall. Work it out yourself if it is not on your results, total cholesterol minus HDL; it is the number your risk is estimated with.

The TC/HDL ratio divides your total cholesterol by your HDL, and so makes visible how your cholesterol is distributed: two people with the same total can have a quite different ratio. Below 5 is the target the one Dutch lab prints, and lower is better.

The atherogenic index of plasma, AIP for short, is the logarithm of your triglycerides divided by your HDL: the same two numbers as the triglyceride/HDL ratio, compressed onto a scale around zero. Below zero means your HDL is larger than your triglycerides, and that is the healthy picture. There is no agreed normal value, and the lower, the better.

The LDL/ApoB ratio is your LDL cholesterol divided by your ApoB, both converted to mg/dl. Every LDL particle carries exactly one ApoB, so the ratio says how much cholesterol each particle holds: the lower it is, the smaller and denser your LDL particles, and those are the particles that most easily lodge in the vessel wall.

ALT is an enzyme from your liver cells that leaks into your blood as soon as those cells come under strain. It is the most sensitive ordinary measure of your liver, and in anyone otherwise healthy a slightly raised value is almost always fatty liver: the condition you can fully reverse with lifestyle.

Albumin is the most abundant protein in your blood, made by your liver. It keeps fluid in your blood vessels and carries calcium, hormones and medicines. The value says whether your liver is producing, whether you eat enough protein and whether you are inflamed, and it colours the results of calcium and zinc.

AST is an enzyme that sits in your liver, but just as much in your muscles and your heart. It leaks into your blood when cells in one of those tissues break down, and so a high AST in anyone who does sport is more often a hard training session than a liver problem; the ratio with ALT tells which of the two.

The AST/ALT ratio divides two liver enzymes that are distributed differently over the body, and so says where a rise comes from: below 1 is usually fatty liver, above 2 in a liver problem is usually alcohol. It only says something when one of the two is genuinely raised.

Bilirubin is the yellow breakdown product of old red blood cells, which your liver makes soluble and drains through the bile. A slightly raised value with otherwise normal liver values is usually Gilbert's syndrome, a harmless variant that occurs in one in twenty people and protects rather than harms.

Gamma-GT is the enzyme of your liver and bile ducts that responds first to everything that quietly burdens the liver: alcohol above all, then belly fat, medicines and a bile drainage that falters. It often moves before ALT rises, and falls within weeks once you cut down.

FIB-4 is a calculation from four numbers you already have, your age, AST, ALT and platelets, that estimates how likely it is that your liver has scars. It is a sieve: a low score all but rules out advanced scarring, and in fatty liver that is exactly the question.

Creatinine is the waste product of your muscles that your kidneys filter out of your blood day and night, and the value is therefore the most common measure of how well your kidneys work. It also depends on how much muscle you have, and that makes reading it a matter of context. A value that stays the same over the years is what you want.

The eGFR is an estimate of how much blood your kidneys filter per minute, calculated from your creatinine, your age and your sex. It is the number your kidney function is read from, and above 60 it is healthy; the trend over the years says more than one value.

Fasting glucose, on your results also written as fasting blood sugar or fasting plasma glucose, is the amount of sugar in your blood after a night without eating: the level your body falls back to once your last meal has long been processed. The value moves late, so the direction within the range says more than one number.

HbA1c, in full haemoglobin A1c and on your results also glycated haemoglobin or GlyHb, is the share of your haemoglobin that glucose has attached itself to, and so the average of your blood sugar over the past two to three months. Read it as a trend beside fasting glucose, triglycerides and HDL; lifestyle shows up in it only after months.

The TyG index is a calculation from your fasting triglycerides and your fasting glucose, meant as an estimate of insulin resistance without insulin having to be measured. Both numbers are on virtually every report. Lower is favourable; above about 4.68 the index fits a body that responds less well to insulin.

The eAG is your HbA1c converted to the average blood sugar of the past two to three months, in the same mmol/L as a glucose meter. It is not a separate measurement but a translation, and it says exactly what your HbA1c already said, in a number you know from your meter.

Eosinophils are the white blood cells of allergy and parasites. The count rises with hay fever, asthma, eczema, a reaction to a medicine or a worm infection, and it falls towards zero through cortisol and prednisone. It is the upper end that means something, and in the pollen season the count naturally sits higher in anyone with hay fever.

Lymphocytes are the white blood cells that recognise viruses, make antibodies and remember what they have seen. The count rises with a viral infection and in the recovery phase after it, and falls through cortisol: with stress, acute illness and prednisone. Always read it beside the neutrophils, because together they say whether it is a virus or a bacterium.

Monocytes are the cleaners of your immune system: white blood cells that move into the tissue, become macrophages there and digest dead cells, bacteria and debris. The count rises in the recovery phase after an infection and with inflammation that has been running a while.

Neutrophils are the largest group of white blood cells and the first on the scene at a bacterium or a wound. The count rises with a bacterial infection, stress, exercise and smoking, and falls after a virus or through medicines. Read the absolute count, not the percentage, and always beside lymphocytes and CRP.

Leukocytes are your white blood cells, the army of your immune system, and the total count says how large that army is in your blood right now. It rises with a bacterial infection, stress and smoking, and falls with a virus or through medicines. The count says that something is going on, and the differential says what.

Basophils are the rarest white blood cells, filled with histamine, and they take part in allergy and in inflammation that has been running a while. A low count is never a finding; a rise is usually mild and says something only in the pattern with the other white cells. Only a count that persistently sits far above the band is taken seriously.

CRP is the protein your liver makes within hours as soon as there is inflammation somewhere in your body, and it is the fastest and broadest gauge of it. It says that something is going on, not where or why, and a low value is the healthy state.

The NLR is your neutrophil count divided by your lymphocyte count, two numbers already in your blood count. The ratio shows where the balance lies between the stress response of your immune system and recovery, and it rises with infection, inflammation, lack of sleep and overtraining.

The SII, in full the systemic immune-inflammation index, is your platelet count times your neutrophil count, divided by your lymphocyte count, three numbers already in your blood count. The index bundles the fast stress response of your immune system, the slower inflammatory response of your platelets and recovery into one number, and it rises with infection, inflammation, lack of sleep and hard training.

Haematocrit is the share of your blood that consists of red blood cells: at 0.45 almost half your blood is cells and the rest plasma. It tells the same story as haemoglobin from another angle, and it is the value that gives away soonest whether your blood is thickened.

Haemoglobin is the protein in your red blood cells that carries oxygen from your lungs to your muscles and brain. The value says how much oxygen your blood can carry, and with that whether you have anaemia; why, ferritin and the cell size tell you. Have blood drawn well hydrated and not after hard exertion.

MCH is the average amount of haemoglobin per red blood cell: how well each cell is filled. It almost always moves with the cell size, low in iron deficiency and high in a deficiency of B12 or folate, and it is one of the first cell values to respond when you top up iron.

MCHC is how densely the haemoglobin is packed in your red blood cells: the filling corrected for cell size. It is the slowest and most stable of the cell values, falls in an iron deficiency that has lasted a while, and a high value is more often a measurement artefact than a finding.

MCV is the average size of your red blood cells. It is the first fork in anaemia: small cells point at iron, large ones at B12, folate or alcohol, and because a red cell lasts four months, MCV is the report of the last few months, not of today.

RDW measures how much your red blood cells differ from each other in size. A low RDW is naturally low and healthy; a high RDW is an early signal that your bone marrow has started making cells of a different size, usually through iron deficiency or a deficiency of B12 or folate.

Erythrocytes are your red blood cells, and this value counts how many circulate per litre of blood. The count does not yet say how much oxygen your blood carries, that depends on how much haemoglobin sits in each cell; together with haemoglobin and the cell size it points at the kind of anaemia. Have blood drawn normally hydrated and not after hard exertion.

Platelets, or thrombocytes, are the smallest particles in your blood and the first to seal a wound. A low number most often comes from clumping in the tube, a virus or alcohol; a high number from an inflammation or iron deficiency.

Ferritin is the protein your body stores iron in, and the value in your blood is the measure of how large that store is. It is the first value to know when you are tired, because the store runs empty long before you have anaemia.

Folate, or folic acid, is the B vitamin from green vegetables and legumes that your cells need to make DNA and divide. Too few vegetables, alcohol and a pregnancy are the most common reasons for a deficiency, and supplements the most common for a high value.

You need vitamin B12 for your nerves, your DNA and making red blood cells. It comes almost only from animal food and has a complicated uptake, so a deficiency comes as often from the stomach as from the plate.

Vitamin D is the hormone your skin makes from sunlight and that lets your gut absorb calcium for your bones and muscles. The blood value is your store of the past weeks, and in the Netherlands it is too low in most people from October to April, unless you top up.

Calcium is the mineral of your bones, and the small part in your blood lets your nerves fire, your muscles contract and your blood clot. Your body holds that part within a narrow band, with PTH and vitamin D as regulators; a high value you take seriously, a low one is usually a matter of protein or vitamin D.

Corrected calcium is a calculation, not a measurement: your total calcium adjusted for your albumin, because half the calcium is bound to that protein. It is the more honest measure when your albumin is low, and unnecessary when your albumin is normal.

Potassium is the mineral your nerves fire with and your muscles contract with, your heart first of all. Almost all of it sits inside your cells, and the small part in your blood is held within a narrow band by your kidneys; too low usually comes from loss, too high often from the draw itself.

Magnesium is the mineral that keeps hundreds of enzymes in your cells at work, from your energy metabolism to your muscles and your heart rhythm. Only one percent of it is in your blood, so the blood value is a coarse measure; a low value is almost always loss through medicines or alcohol.

Sodium is the salt in your blood, and the value is not about how much salt you eat but about how much water you hold on to. Your brain and kidneys keep it within a band of less than ten units, because your brain cells swell or shrink with every shift.

TSH is the hormone your brain uses to steer your thyroid, and it works like a thermostat: if the thyroid delivers too little, TSH rises, if it delivers too much, TSH falls. That makes TSH the most sensitive value to see whether your thyroid is in balance, long before the thyroid hormones themselves deviate.

Free T4 is the thyroid hormone circulating freely in your blood right now, not bound to protein, and therefore the part that actually reaches your cells. It says what your thyroid delivers, where TSH says what your brain asks; together they tell whether your thyroid is underactive, overactive or in balance.