What does "normal range" really mean?
On every lab report you will see a column labelled Reference Range or Normal Values. These numbers are not arbitrary — they come from real science. Here is how Blood Sciences experts work them out, and what the result really tells you.
How the range is calculated
To set a reference range, scientists collect blood samples from thousands of carefully selected healthy people in the population. Every result is analysed and the spread of values is measured. The range published on your report is the band where approximately 95% of healthy people fall.
That means even in a perfectly healthy group, around 1 in 20 results will naturally land just outside the range. A result outside the band is a clue, not a verdict.
If your result is INSIDE the range
You are within the average healthy group. That is reassuring — but it does not 100% guarantee that everything is fine. Some conditions develop slowly, or affect different people in different ways. Treat it as a good sign, not a final answer.
If your result is OUTSIDE the range
You are outside the average group. That does not automatically mean you are sick — it simply means your body is working differently, and it is worth understanding why. Look at the size of the difference, your symptoms, your history, and what other tests are doing at the same time.
Ranges depend on YOU
- Age: children and seniors have different normals.
- Sex: men and women have different ranges for many tests (haemoglobin, creatinine, hormones).
- Pregnancy: many ranges shift significantly.
- Ethnicity & altitude: can affect haemoglobin and kidney calculations.