Patient education: Understanding lab test results (The Basics)

Are there different types of lab tests? — 

Yes. Doctors can order many different laboratory, or "lab," tests. Lab tests can be done on a sample of blood, urine, or other body fluids or tissues.

In the lab, the sample is examined or tested. For example, the staff might check for or measure certain substances or chemicals.

Why might I need a lab test? — 

Your doctor can order lab tests to learn more about your health. This is done in different situations, including:

●As part of a routine checkup – Even if you are healthy, your doctor might order routine lab tests. Common examples include tests to check cholesterol, blood sugar, and complete blood count. If a routine test finds that there might be a problem, your doctor might do more tests or suggest treatment. It can also be useful to compare recent results with older ones.

●To try to figure out what is causing your symptoms

●To "screen" for health problems – Screening means checking for a problem before a person has any symptoms.

●If you have a known health condition – In this case, lab tests can give information about whether your condition has changed. They can also be used to learn about how treatment is working.

When will I get my results? — 

It depends. With some tests, results are available very quickly, sometimes even the same day. With others, it can take a few days or weeks to get results. Your doctor or nurse will tell you when to expect your results.

If you use an online "patient portal," you might get an alert there when your results are ready. Sometimes, you will see your results before your doctor has reviewed them. But it's important to review your results with your doctor or nurse. This way, they can explain exactly what the results mean and whether there is anything else you need to do.

What do my test results mean? — 

They can give information about your health. Different things are measured in different ways.

Depending on the test, your results might include terms like:

●"Positive" or "negative" – Positive means that the test found what it was checking for. Negative means that it did not.

●"High" or "low" – Some health problems cause certain substances in your body to increase or decrease.

●A number – Some tests measure the specific amount or level of a substance. This can appear in different units, for example, "mg/dL" or "mIU/mL." Other tests give a percentage.

Sometimes, the results are "inconclusive." This means that the results are not certain. Your doctor might repeat the test to see how the result changes over time. You might need other tests, too.

Should I worry if my test results are abnormal? — 

It can be scary to get an abnormal lab test result. But try not to worry right away.

An abnormal test result sometimes means that there is a problem, but not always. For example:

●Your result could be just a little bit above or below what the lab defined as "normal." Different labs use different numbers for this. These are called "references ranges."

●Something temporary could be affecting your test results. Some results can change if you recently ate, exercised, or took certain medicines. For example, for a "fasting" blood sugar, you need to avoid eating or drinking anything for at least 8 hours before the test. Eating or drinking before the test can raise your blood sugar.

●There could be a "false positive" or "false negative":

•False positive – This is when the results show that the test found something, but you do not have a problem.

•False negative – This is when the results show that the test did not find what it was checking for, but you do have a problem.

False-positive or false-negative results can happen for different reasons. For example, the sample might have been collected or measured improperly.

●It is possible to get a "lab error," meaning that something went wrong with the test itself.

If your doctor thinks that your results might be inaccurate, they will probably have you repeat the test. They might ask you to go to a different lab.

If your test results are abnormal, your doctor will talk to you about what it means and what to do next.

What if I have questions about my results? — 

Talk to your doctor or nurse. They can help you understand your test results. If they think that you might have a health problem, they will also talk to you about what to do next. In some cases, you might need more tests.

Your doctor or nurse will also consider things like your symptoms, past medical problems, and "family history." (This means whether certain diseases run in your family.)

If you do have a health problem, your doctor will work with you to come up with a plan for treatment.