Lab tests are used in many different ways. Your health care provider may order one or more lab tests to:
Diagnose or rule out a specific disease or condition
Screen - A screening test can show if you are at a higher risk for getting a specific disease. It can also find out if you have a disease, even if you have no symptoms.
Monitor a disease and/or treatment - If you've already been diagnosed with a disease, lab tests can show if your condition is getting better or worse. It can also show if your treatment is working.
Check your overall health - Lab tests are often included in a routine checkup.
Lab results are often shown as a set of numbers known as a reference range. A reference range may also be called "normal values." You may see something like this on your results: "normal: 77-99mg/dL". Reference ranges are based on the normal test results of a large group of healthy people. 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. 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.