Genetic testing is a type of medical test that looks for changes, sometimes called variants or mutations, in your DNA. DNA contains the genetic instructions in all living things. Often, these changes have no effect, but sometimes, even a small change in DNA can cause disease or other health conditions.

Genetic tests take a sample of your blood or tissues and check your cells to look for any changes in:

• Genes are parts of DNA found in your cells that carry information that controls what you look like and how your body works. Many genes tell your body how to make proteins, which are needed for your body to work correctly.
  • Genome sequencing is a process that checks all your DNA.
  • Exome sequencing is a process that only checks the parts of your DNA that provide instructions to make proteins.
• Proteins do most of the work in your cells. If there are changes in the amount and activity level of proteins, they might be due to changes in the genes that produce those proteins.
• Chromosomes are thread-like structures in your cells. Each chromosome is made up of DNA tightly packaged around proteins. People usually have 23 pairs of chromosomes that contain all their DNA.

Most of the time, genetic testing is done through your health care provider. This is called clinical testing. It is done to find out about an inherited disorder (passed down through families) and to help make decisions about your care.

Other ways to get genetic testing include:

• Research-based testing is a genetic test done as part of a research study (clinical trial).
• Direct-to-consumer (DTC) testing is a genetic test that allows you to send a DNA sample and get the results. You may do this to learn about your ancestry or your risk for certain diseases.

Genetic testing may be done for many different reasons, including to:

• Find genetic diseases in a fetus. This is a type of prenatal testing.
• Screen newborn babies for certain treatable conditions.
• Lower the risk of genetic diseases in embryos that were created using assisted reproductive technology.
• Find out if you carry a gene for a certain disease that could be passed on to your children. This is called carrier testing.
• See whether you are at an increased risk of getting a specific disease. This may be done for a disease that runs in your family.
• Diagnose certain diseases.
• Identify genetic changes that may be causing or contributing to a disease that you were already diagnosed with.
• Help guide your provider in deciding the best medicine and dosage for you. This is called pharmacogenomic testing.
• To check for, monitor, or manage a disease. This is sometimes used to help find the best cancer treatment.
• To confirm the biological father (paternity) of a child, or how much genetic information is shared with other relatives.
• To explore the likelihood of having or developing certain physical traits, such as hair color or facial dimples, or to learn about your ancestry.
• To help advance our understanding of genetic conditions, learn how genes work, and find unknown genes.

Genetic tests are often done on a blood or cheek swab sample. But they may also be done on samples of hair, saliva, skin, amniotic fluid (the fluid that surrounds a fetus during pregnancy), or other tissue. The sample is sent to a laboratory. There, a lab technician will use one of several different techniques to look for genetic changes.

The benefits of genetic testing include:

• Helping your provider make recommendations for the management or monitoring of a genetic condition.
• Giving you more information for making decisions about your health and your family's health:
  • If you find out that you are at risk for a certain disease, you might take steps to lower that risk. For example, you may find out that you should be screened for a disease earlier and more often. Or you might decide to make healthy lifestyle changes.
  • If you find out that you are not at risk for a certain disease, then you can talk to your provider about when it would be appropriate to schedule checkups or screenings.
  • A test could give you information that helps you make decisions about having children.
• Identifying genetic disorders early in life so that treatment can start as soon as possible.

The physical risks of the different types of genetic testing are small. But there can be emotional, social, or financial drawbacks:

• Depending on the results, you may feel angry, depressed, anxious, or guilty. This can be especially true if you are diagnosed with a disease that does not have effective treatments.
• Despite the protections that are in place, you may be worried about genetic discrimination in employment or insurance.
• Genetic testing may give you limited information about a genetic disease. For example, it cannot tell you whether you will have symptoms, how severe a disease might be, or whether a disease will get worse over time.
• Genetic testing results might be inconclusive. For example, you might keep getting negative results or not get an answer at all.
• Some genetic tests may give you results that you didn't expect. For example, if you are tested to check for the cause of a rare disease, and a different variant is found that puts you at increased risk for something else that was previously unknown.
• Some genetic tests are expensive, and health insurance might only cover part of the cost. Or they may not cover it at all.

The decision about whether to have genetic testing is complex. In addition to discussing the test with your provider, you can meet with a genetic counselor. Genetic counselors have specialized degrees and experience in genetics and counseling. They can help you understand the tests and weigh the risks and benefits. If you do take a test, they can explain the results and make sure that you have the support that you need.