Introduction

Lab tests play an important role in your health care. They help your doctor make a diagnosis or treatment decisions. But they may not provide all of the information that your doctor needs.

Your doctor will not usually make a decision or diagnosis based only on the results of a lab test, unless the test results are clear. Instead, the doctor will use test results along with information about your health, age, and other factors.

Making sense of your lab test involves more than just knowing why the test is done. It's also important to understand what the results mean and what can affect the results. Sometimes when you last ate or exercised can affect results. Medicines or natural health products and your age also can affect them.

Why did you have a test?

There are many reasons for lab tests. You may feel fine and still have a test, such as when you have an annual physical exam.

You may have a test to:

• Find the cause of symptoms.
• Confirm a diagnosis.
• Screen for a disease.
• Find out how serious a disease is.
• Find out if a treatment is working.
• Make sure medicines are not causing a problem.

What do the numbers mean?

Many test results come back in the form of numbers. Experts test many healthy people to find out what is normal for that group. The numbers they come up with are called a reference range. Your doctor will look at a reference range to help find out what your numbers mean.

Your test results could fall in or outside this range. The test is most often considered normal when the numbers are within the range. But it's possible that your numbers can fall outside the range and still be normal for you. Your doctor will look for any patterns of abnormal lab results that may be related to a health problem.

Lab tests are only one piece of information about how you're doing. Your doctor considers many things when looking at your health. These things may include your symptoms, age, weight, physical exam, and family history.

How can you get help understanding the results?

You can learn more about your lab results in several ways. Ask your doctor to explain what the results mean. Prepare questions before you visit your doctor so you don't forget them. Don't be afraid to ask questions. If you don't understand the answer, ask again.

The person you talk to about your results may not be a doctor. You might also get information from a nurse or a physician's assistant.

Your doctor's office may have a website where you can get help with lab test results. You can also look on a trusted online medical information site.