Blood test results explained

Your blood test results are in. What you get is a table of abbreviations, numbers and the odd asterisk. With a few keys, that report becomes far easier to read: what each line measures, what the range next to it means, and when a result is worth raising with your doctor. In this article we walk through the lines you'll see most often on a Belgian lab report.

How to read a lab report

Every line on your report has the same parts:

• The test name: often an abbreviation, such as Hb or TSH.
• Your result: the value the lab measured in your blood.
• The unit: for example g/dL or mg/dL. Units sometimes differ between labs, so only compare numbers in the same unit.
• The reference range: the values the lab finds in healthy people.

A value outside that range is usually flagged, with an asterisk, an arrow or a number in bold. Every lab does this its own way.

What the reference range means

The reference range is not a line between healthy and ill. It's the range that 95% of results from healthy people fall into. That also means 5% of healthy people fall outside it, with nothing wrong.

A few things worth knowing:

• Every lab has its own range. Methods and equipment differ. Always look at the range printed next to your own result.
• A single result outside the range says little on its own. Values vary from day to day, and depend on what you ate, how you slept and whether you've just been ill.
• The more tests, the more likely an asterisk. On a report with forty lines, one or two small deviations are entirely normal.
• For some values, your doctor looks beyond the range. With cholesterol, what's right for you depends on your overall risk of heart and blood vessel disease.

Full blood count

The full blood count counts and measures your blood cells. It's nearly always at the top.

• Haemoglobin (Hb): the protein in your red blood cells that carries oxygen. A low value can point to anaemia.
• Haematocrit (Hct): the share of your blood made up of red blood cells.
• Red blood cells (RBC): the number of red blood cells.
• MCV, MCH and MCHC: how big your red blood cells are on average and how much haemoglobin they hold. They help your doctor find the cause of anaemia. Read more in MCV, MCH and MCHC.
• RDW: how much your red blood cells vary in size.
• White blood cells (WBC): your immune cells. They often rise for a while during an infection.
• Platelets: the cells that help your blood clot.

Cholesterol and blood fats

• Total cholesterol: all the cholesterol in your blood together.
• LDL cholesterol: the 'bad' cholesterol, which can build up in your blood vessels.
• HDL cholesterol: the 'good' cholesterol, which clears away excess cholesterol.
• Triglycerides: fats in your blood. They rise after a meal, which is why your doctor sometimes asks you to come fasting.

Blood sugar

• Glucose: your blood sugar at the moment of the draw. Whether you fasted makes a big difference here.
• HbA1c: your average blood sugar over the past two to three months. One sugary breakfast barely moves it.

Kidneys

• Creatinine: a waste product from your muscles that your kidneys filter out of your blood. People with a lot of muscle often have a slightly higher value.
• eGFR: an estimate of how well your kidneys filter, calculated from your creatinine, age and sex.

Liver

• ALT and AST: enzymes from your liver cells. They rise when liver cells are under strain, for example with a fatty liver, alcohol or some medicines.
• Gamma-GT: a liver enzyme that responds to alcohol and to the bile ducts, among other things.
• Alkaline phosphatase: an enzyme from your liver, bile ducts and bones.

Iron, thyroid, inflammation and vitamin D

• Ferritin: your iron stores. A low value points to a shortage. Inflammation can raise ferritin, which sometimes hides a shortage.
• TSH: the hormone your brain uses to steer your thyroid. A high TSH fits a slow thyroid, a low TSH an overactive one.
• CRP: a protein that rises with inflammation or infection. hs-CRP measures the same protein more sensitively, and picks up mild inflammation too.
• Vitamin D: usually measured as 25-OH vitamin D. In Belgium it's often lower in winter, when your skin gets little sun.

A value outside the range: what next?

An asterisk is a reason to talk, not a diagnosis. Your doctor looks at the whole picture: your symptoms, your history, your medicines and the rest of your results.

• Go through your results with your GP, especially if you're unsure what a flag means.
• Jot down your questions beforehand: which value, since when, and whether you have symptoms that fit.
• Compare with earlier results. A value that has sat just outside the range for years is different from a sudden change.
• Sometimes a repeat test is all it takes. Many small deviations are gone at the next measurement.
• Hold off on supplements based on a single value. Too much iron or vitamin D isn't good either.

Conclusion

Your lab report is less cryptic than it looks. Each line measures something concrete, and the range next to it shows where most healthy people sit. An asterisk is a question, not an answer. Take your report to your GP and go through it together. Want all your values in one overview? Synapse reads the PDF from your lab and explains every value in plain language.

Sources

NVKC - What do the reference values on my result mean?

NVKC - Full blood count

Gezondheid en Wetenschap - Lab tests by the GP

American Family Physician - Evaluation of Microcytosis