Reference ranges are based on the normal test results of a large group of healthy people.
Lab results are often shown as a set of numbers known as a reference range. The range helps show what a typical normal result looks like.
But not everyone is typical. Sometimes, healthy people get results outside the reference range, while people with health problems can have results in the normal range. A reference range may also be called 'normal values.' You may see something like this on your results: 'normal: 77-99mg/dL' (milligrams per deciliter). If your results fall outside the reference range, or if you have symptoms despite a normal result, you will likely need more testing.
Your lab results may also include one of these terms:
Negative or normal, which means the disease or substance being tested was not found
Positive or abnormal, which means the disease or substance was found
Inconclusive or uncertain, which means there wasn't enough information in the results to diagnose or rule out a disease. If you get an inconclusive result, you will probably get more tests.
Tests that measure various organs and systems often give results as reference ranges, while tests that diagnose or rule out diseases often use the terms listed above.
A few tests do not have ranges, but limits at which decisions are made about whether you are healthy or should be treated. Through many years of research involving large, diverse populations, these limits have become standardized. The specific reference ranges that appear on your laboratory report are determined and provided by the laboratory that performed your test.
Reference ranges help describe what is typical for a particular group of people based on age, sex, and other characteristics. An example is glucose testing for diabetes.
Each laboratory establishes or 'validates' its own reference ranges, thus reflects differences that vary from lab to lab. In the context of your personal information, you and your provider can use reference ranges as a guide to what your results mean and to help make decisions about managing your health.