Library · Method
Lab test reference range
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A lab test's reference range is the band between two numbers, one low and one high. Results that fall inside that band are the ones considered normal.
Where do those two numbers come from? From the results of the same test in large groups of healthy people. It's like a clothing size: it comes from measuring lots of healthy people, not one person. The same test can have different ranges for different groups of people. And because labs often work with different methods, they often use different ranges too.
Here's the important part: because the range varies, the word "normal" can be misleading. A result outside the range may or may not be a sign of a health problem. And a result inside the range is not always a guarantee of good health.
In brief
A lab test's reference range is the pair of numbers marking the low and high ends of results considered normal.
It comes from results in large groups of healthy people; it can vary between groups, and since labs often use different methods, they often use different ranges too.
Like a clothing size: it comes from measuring lots of healthy people.
That is why "normal" can be misleading: a result outside the range may or may not signal a problem, and one inside it doesn't always guarantee good health.
Sources (1)
- MedlinePlus, U.S. National Library of MedicineHow to Understand Your Lab Results, MedlinePlusPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated