Genetic testing analyzes your DNA, chromosomes, or proteins to look for changes linked to health conditions, inherited traits, or how your body processes medications. Tests range from simple cheek swabs that screen for a single gene variant to complex sequencing that reads your entire genetic code. The results can confirm a diagnosis, reveal whether you carry a condition you could pass to your children, or estimate your risk of developing a disease later in life.
How Genetic Testing Works
At the most basic level, genetic tests examine the sequence of chemical building blocks in your DNA to spot changes, or variants, that may cause or increase the risk of disease. Some tests zoom in on a single gene, while others scan large stretches of chromosomes or even the whole genome. The approach depends on what your doctor is looking for.
Chromosomal tests look at the big picture: extra or missing copies of entire chromosomes, large deleted segments, or pieces that have swapped places between chromosomes. These kinds of changes are behind conditions like Down syndrome, where there is an extra copy of chromosome 21. More targeted molecular tests read the letter-by-letter code of specific genes to find small mutations, the kind responsible for conditions like cystic fibrosis or sickle cell disease. A third category, biochemical tests, skips the DNA entirely and instead measures whether certain proteins or enzymes are working normally, since abnormal levels can signal an underlying genetic problem.
Samples are usually collected through a blood draw, a painless cheek swab, or a skin sample. During pregnancy, a small amount of amniotic fluid or placental tissue can be collected for prenatal testing. Newborn screening uses a few drops of blood from a heel prick.
Types of Genetic Tests and Why They’re Ordered
Genetic testing isn’t one-size-fits-all. The reason you’re being tested shapes which type of test is used.
- Diagnostic testing confirms or rules out a suspected condition when symptoms are already present. If a child shows signs of cystic fibrosis, for example, a diagnostic gene test can provide a definitive answer.
- Predictive testing estimates your risk of developing a condition before any symptoms appear. People with a family history of certain cancers, like hereditary colorectal cancer, sometimes use predictive testing to guide screening decisions.
- Carrier testing reveals whether you carry a gene variant for a condition you don’t have yourself but could pass to a child. This is common for couples planning a pregnancy, especially when there is a family history of conditions like sickle cell disease or Tay-Sachs. Expanded carrier screening panels can check for dozens of conditions at once.
- Prenatal testing checks for genetic conditions in a developing baby. Screening tests, like cell-free DNA testing done through a simple blood draw from the pregnant person, estimate the likelihood of conditions such as Down syndrome or trisomy 18. Diagnostic prenatal tests like amniocentesis or chorionic villus sampling provide more definitive results but are slightly more invasive.
- Newborn screening is required in every U.S. state. It tests for a panel of genetic and metabolic conditions so that treatment can start immediately. Phenylketonuria (PKU) and sickle cell disease are two well-known examples.
- Preimplantation testing is used during in vitro fertilization (IVF) to check embryos for specific genetic conditions before implantation.
- Pharmacogenetic testing looks at genes that affect how your body breaks down medications. Variations in drug-processing genes can mean a standard dose is too strong or too weak for you. The FDA maintains a list of gene-drug pairs where dosage adjustments are recommended. For instance, people who metabolize certain psychiatric medications very slowly may need a lower dose to avoid side effects, while others may need a higher dose to get the same benefit.
Home Kits vs. Clinical Tests
Direct-to-consumer (DTC) genetic tests, the kind you order online and do with a saliva sample at home, are widely available and typically cost anywhere from under $100 to several thousand dollars depending on how much of the genome they analyze. They can be an interesting starting point for exploring ancestry or general health traits, but they have significant limitations when it comes to medical decisions.
The most important distinction is that DTC tests are screening tools, not diagnostic ones. They cannot confirm that you have a disease. Research comparing DTC results to clinical-grade testing found a false positive rate of 40% for pathogenic gene variants, meaning nearly half the people told they had a dangerous variant actually did not when retested in an accredited lab. Results also vary between companies, and most clinical geneticists consider DTC findings unreliable for guiding healthcare decisions.
Regulation is another gap. DTC companies operate as commercial entities, not medical providers. They have no duty of care toward customers and no obligation to follow the same ethical standards that govern clinical genetics. The consent process in a DTC purchase agreement is not equivalent to the informed consent you receive in a medical setting. If a DTC test flags something concerning, the next step is confirmatory testing through a healthcare provider, and that follow-up care is generally covered by insurance even though the original DTC test is not.
Understanding Your Results
Genetic test results typically fall into one of three categories: positive (a disease-linked variant was found), negative (no variant was detected), or a variant of uncertain significance, commonly abbreviated VUS. A VUS means the lab found a genetic change but there isn’t enough scientific evidence yet to say whether it actually causes disease. The vast majority of new variants identified in any person’s genome fall into this uncertain category. A VUS can be frustrating, but it doesn’t mean something is wrong. It simply means scientists haven’t studied that particular change enough to classify it.
A positive result doesn’t always mean you will develop a condition. For many diseases, a gene variant increases risk rather than guaranteeing an outcome. Lifestyle, environment, and other genes all play a role. Conversely, a negative result doesn’t guarantee you’ll stay healthy, especially if the test only screened for a limited set of variants.
The Role of Genetic Counseling
A genetic counselor is a healthcare professional trained to help you make sense of genetic information. Before testing, a counselor collects your personal and family health history and uses it to assess whether testing is likely to be informative for your situation. They help you weigh the potential benefits, limitations, and emotional implications of learning your results.
After testing, the counselor walks you through what the results mean in practical terms: your actual risk level, what treatment or surveillance options exist, and how the findings might affect family members. They can also connect you with specialists, support groups, and advocacy organizations. For results that carry emotional weight, like a positive test for a late-onset neurological condition, this support can be especially valuable.
Cost and Insurance Coverage
Costs vary widely. A targeted single-gene test ordered by a physician may cost a few hundred dollars, while whole-exome or whole-genome sequencing can run into the thousands. When a doctor orders genetic testing for a medical reason, health insurance often covers it, particularly when there is a documented family history or clinical indication. Coverage policies differ between insurers, so checking beforehand is worthwhile.
DTC tests are almost never covered by health insurance because they are purchased without a medical referral and aren’t considered diagnostic. You may be able to use a flexible spending account (FSA) or health savings account (HSA) if the test includes health-related information. Ancestry and paternity tests generally don’t qualify for FSA or HSA reimbursement.
Privacy and Legal Protections
In the United States, the Genetic Information Nondiscrimination Act (GINA) prohibits health insurance companies and employers from discriminating against you based on your genetic information. That definition is broad: it covers your own test results, the test results of family members, and even your family’s disease history. Under GINA, a health insurer cannot deny you coverage or raise your premiums because of a genetic variant, and an employer cannot use genetic information in hiring, firing, or promotion decisions.
GINA has a notable gap, though. It does not apply to life insurance, disability insurance, or long-term care insurance. Companies that sell these policies can legally ask about and use genetic test results when making coverage decisions. This is worth considering before testing, especially for conditions with significant financial implications. Some states have passed their own laws to fill this gap, but protections vary.