Published: 30 Sep 2024

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. The range helps show what a typical normal result looks like.
But not everyone is typical. 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). Reference ranges are based on the normal test results of a large group of healthy people. Sometimes, healthy people get results outside the reference range, while people with health problems can have results in the normal range. 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.Lab results are often shown as a set of numbers known as a reference range.

However, there are also optimal health ranges that are those that appear to have the optimal health impact on people. In contrast, optimal (health) range or therapeutic target is a reference range or limit that is based on concentrations or levels that are associated with optimal health or minimal risk of related complications and diseases. It is a basis for a physician or other health professional to interpret a set of results for a particular patient. Reference ranges are usually given as what are the usual (or normal) values found in the population, more specifically the prediction interval that 95% of the population fall into. More specifically, optimal levels are generally close to a central tendency of the values found in the population. For most substances presented, the optimal levels are the ones normally found in the population as well. Reference range or reference interval usually describes the variations of a measurement or value in healthy individuals. The standard definition of a reference range (usually referred to if not otherwise specified) basically originates in what is most prevalent in a reference group taken from the population. This may also be called standard range. However, usual and optimal levels may differ substantially, most notably among vitamins and blood lipids, so these tables give limits on both standard and optimal (or target) ranges.