Lab Test Results: What to Expect

If you’re waiting for lab test results to come back or you’re trying to figure out what they mean, the process and all those medical terms and numbers can be confusing.

There are thousands of lab tests, and their results can mean different things. But a few general guidelines can help shed some light.

How do doctors use lab tests?

Nobody likes to get poked with a needle or pee in a cup. But lab tests are important tools, and doctors use them in a few different ways:

  • To check on how you’re doing generally, like cholesterol or blood sugar tests when you have a physical
  • To answer a specific question, like “Do you have strep throat?”
  • To track an ongoing condition or see how treatment is working

How long does it take to get results?

That depends on the test. Some can be done right in the office or a nearby lab, so you may have the results that day or the next. Other tests may take days or weeks, especially if they have to be sent to a specific kind of lab.

Before you leave your doctor’s office, ask when you’ll know the results. And ask the office staff to let you know when they’re in. (Some offices might not call if you don’t request it, especially if the results are in the normal range.)

What do my results mean?

Here are a few things to look for:

Positive vs. Negative. Some lab tests answer yes-or-no questions like whether you’re pregnant or have certain kinds of infections. These results are usually written as “positive” or “negative.” In this case, positive doesn’t necessarily mean “good” and negative doesn’t necessarily mean “bad.” Instead:

  • Positive: The lab found whatever your doctor was testing for. So if you had a test for strep throat, testing positive means you do have strep throat.
  • Negative: The lab didn’t find whatever you were tested for. A negative result for strep throat means that the lab didn’t find any strep bacteria in the sample, so you probably don’t have it.

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Sometimes, the result might be “inconclusive.” That means the lab doesn’t have a clear yes or no answer based on your sample. Your doctor may want you to do the test again or have another kind of test.

Reference Ranges. A lot of lab test results don’t give clear answers. Instead, they’re shown as a number -- like your cholesterol levels.

These numbers don’t mean anything on their own, so you have to see how yours compare to a healthy range called your “reference range” or “reference value.” You’ll see this range on the lab test results.

Are lab test results always right?

While they do have to meet very high standards, they can be wrong sometimes. For example, you might get a false positive (the results say you have the condition you were tested for, but you really don’t) or a false negative (the results say you don’t have a condition, but you really do).

Lots of things can affect certain lab test results, like:

When you get your results, ask your doctor how accurate the test is. If your doctor thinks your results may not be right, she may recommend that you do the test again or take a different test.

What if my lab results aren’t “normal”?

It’s easy to be concerned if you see words like “abnormal” on your results. But that’s not all that unusual. For example, if your results are just outside the reference range, it may not necessarily be a problem.

If you’re worried about any of your results or have any questions, call your doctor’s office. You can talk to a nurse or schedule an appointment with your doctor to talk about them. She can help you understand what your results mean for you.

Lab Test Tips

Always keep a copy of your results. This can be useful in case you switch doctors, need to show them to a specialist, or just want to look at them again later.

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Remind your doctor if you take medications or have a health condition that can affect your results. That should be in your record, but it’s still a good idea to mention it.

Be honest if you didn’t follow the instructions. With some lab tests, you’re supposed to fast (not eat), or not do certain activities, eat certain foods, or take certain drugs. If you forget and mess up, don’t worry -- just tell your doctor before you do the test. It’s not a big deal to reschedule, and it’s a waste of time to get the test if the results won’t be right.

Make sure your doctor always uses the same lab to do your tests if possible. It can be hard to compare results from different labs because they may approach the test differently. For example, one lab might have different ranges for “normal” and “abnormal” than another.

Ask your doctor questions about your results like:

  • Why did I need this test?
  • What exactly does this test result mean?
  • How accurate is this test?
  • When will I need to do this test again?
  • Based on my results, do I need treatment or other tests?
WebMD Medical Reference Reviewed by Melinda Ratini, DO, MS on November 25, 2017

Sources

SOURCES:

National Center for Policy Analysis: “Patients Get Direct Access to Lab Tests.”

FDA: “Tests Used In Clinical Care.”

HealthResearchFunding.org: “Kaiser Permanente Blood Test Results Explained.”

Healthy Women: “You Have a Right to Your Lab Results: New Rules Provide Direct Access.”

American Association for Clinical Chemistry’s Lab Tests Online: “Reference Ranges and What They Mean,” “Strep Throat Test,” “Deciphering Your Lab Report,” “Test Preparation: Your Role,” “Making Informed Decisions for Better Health.”

U.S. Department of Veterans Affairs: “HIV/AIDS: Frequently Asked Questions.”

National Cancer Institute: “Understanding Laboratory Tests.”

Dana-Farber Cancer Institute: “What Are False-Positive Test Results, and What Causes Them?”

ASCO’s CancerNet: “3 Steps to Building a Personal Medical Record.”

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