Genes are the biological blueprints we inherit from our parents. They contain the information that makes us who we are. Some genes determine what color your eyes and hair are, or even how the herb cilantro tastes to you (delicious or soapy!). Some genes are an indication of where your ancestors came from. Others can predict athletic ability. But genes are also an important factor in your health, both present and future.

Genetic testing, also called DNA testing, can identify mutations in specific genes. These changes can show if you have or are at increased risk of developing certain conditions, such as cancer or Alzheimer’s disease.

Having a genetic test is usually a simple matter of giving a small sample of blood or saliva. The sample is sent to a lab, which tests for the specific genes, gene markers, or gene mutations that might be relevant to your health.

“Getting people comfortable with genetics and learning about it, and how it might impact themselves and their families, I think that’s all a good thing,” Dr. Christine Eng, professor of molecular and human genetics at the Baylor College of Medicine, told Fortune.com.

It’s never too late to make changes for good health, and genetic testing can help you do just that. Here’s what you need to know about how medical genetic testing might help you to get and stay healthy.

Genetic testing for screening and prevention

If you know your genes are increasing your risk of a disease, you can modify some of your behaviors in order to lower the risk of developing it. In other words, genetic tests can give you insight into your health risks so you can make decisions based on that information. You might decide to change your diet, start on specific medication, or have screening tests more regularly, depending on what you’re found to be at increased risk for.

If several people in your family had colon cancer, for example, you might want to find out if you’re at greater risk of developing that cancer, too. If you know you have a mutation that makes you more susceptible, you might choose to take some preventive steps. You might change your diet. You could also have more frequent colonoscopies or other tests so that if you do develop colon cancer it’s found early when it can be more easily treated.

Another gene, called BrCa, has been linked with familial breast and ovarian cancer. Women who know they have a BrCa mutation can decide to get mammograms or other breast imaging tests more frequently so that if cancer does develop, it’s detected early. Or they can even decide to have surgery to remove their breasts or ovaries to prevent the cancer from ever developing.

Not every disease risk can be predicted with genetic testing, but some of those that can now be tested for include:

• Alzheimer’s disease
• Specific cancers (breast, colon, ovarian, prostate)
• Cystic fibrosis
• Diabetes
• Heart disease
• Huntington’s disease
• Parkinson’s disease
• Sickle cell disease

Ask your internist or medical provider if anything in your or your family’s medical history makes them believe that genetic testing might be a good part of your health plan.

Other reasons for genetic testing

If you’ve been diagnosed with a disease like breast cancer, you may be surprised if your doctor wants to do a genetic test. But post-diagnostic testing can provide several benefits.

Guiding treatment decisions

By finding out the exact mutation, your healthcare provider can tailor a cancer treatment that works best for your specific cancer.

Giving valuable information for family members

Sharing health info with family members gives them a chance to take proactive steps in safeguarding their own health.

Helping researchers

If you opt to share your data—anonymously—with researchers, you contribute to an increasing body of information that scientists can use to help them understand how genetics affects human health.

What to consider before getting genetic testing

There are many important reasons to get genetic testing, such as diagnosing illness, determining which treatment might work best, or finding out important familial health risks. But it’s good to be aware of some limitations and concerns around genetic testing, too.

Your genes are not your fate

Even the best genetic tests just indicate that something might or probably will happen. . . not that it definitely will. Getting a positive result on a genetic test doesn’t mean that you’ll definitely develop a specific condition. On the other hand, getting a negative result doesn’t mean you definitely won’t. Most diseases and medical conditions are caused by a combination of several genes plus lifestyle factors.

Genetic testing can cause distress

Finding out you have a high risk of developing something that can’t be cured, like Alzheimer’s disease, can be extremely upsetting. That’s why it’s important to speak with a genetic counselor who can help you understand your results and decide how you want to act on them. You might, for instance, decide to retire earlier and travel more. Or take the opportunity to make financial or legal arrangements.

Your privacy matters

Genetic data can be very sensitive. Before you agree to genetic testing, you should understand how the information will be used and whom it will be shared with. Ask your doctor for detailed information about what the privacy policy is and how the information will be stored and protected.

Health insurance companies can’t discriminate

Many people worry that a positive result on a genetic test could cause health insurance companies to deny coverage or raise their premiums. The good news is that the Genetic Information Nondiscrimination Act, passed in 2008, prohibits this practice. Unfortunately, though, this law doesn’t prevent other types of insurance companies—life insurance, disability insurance, and long-term care insurance—from using genetic information in their decision making.

Medicare coverage for genetic testing

Original Medicare does offer limited coverage for genetic testing. If you’re diagnosed with cancer and meet certain other criteria, Medicare may cover testing to see if a gene mutation is involved. Genetic testing can also be used to help your doctor diagnose a medical condition and to guide any necessary treatment.

Medicare does not cover preventive screening genetic testing, with the exception of Cologuard, the colorectal cancer test.

In order to be covered, the genetic tests must be considered medically necessary and must be FDA approved. Additionally, the tests must be requested and received by a physician. Home genetic tests are not eligible for coverage, with the one exception of Cologuard.

Medicare Advantage plans cover everything that Original Medicare does, plus often provide coverage for dental, eye exams, gym memberships, and more. Check out our easy-to-use Find a Plan tool to compare Medicare plans in your area.

Additional resources

• ClearMatch Medicare: Find a Medicare Plan
• Fortune: How Accurate Are Commercial Genetic Tests?