A DNA test can reveal whether you carry certain genetic variants that increase your risk of disease, help explain an inherited medical condition, or influence how your body responds to particular medications. Depending on the test, it may also identify whether you could pass a genetic condition to your children or help doctors choose a more appropriate treatment.
But genetic testing cannot predict your entire medical future. Most common health conditions develop through a combination of genetic factors, environmental exposures, lifestyle, aging, and chance. Even when a test identifies a variant associated with a disease, it does not always mean the disease will develop.
Understanding what a DNA test can—and cannot—tell you begins with how genes influence health, what different genetic tests measure, and how their results should be interpreted.
How your DNA influences your health
DNA, or deoxyribonucleic acid, contains the biological instructions that help cells grow, function, and reproduce. These instructions are organized into genes, which provide directions for making proteins and other molecules essential to the body.
Most people inherit one copy of each autosomal gene from each biological parent. The particular versions of genes a person inherits contribute to traits such as blood type, hair texture, and aspects of how the body processes nutrients or responds to infections and medications.
Genetic differences can also affect health. A variant is a difference in a DNA sequence. Some variants have little or no effect on health, while others alter how a protein functions, change the amount of protein a cell produces, or affect biological processes that protect the body from disease.
For example, certain inherited variants in the BRCA1 and BRCA2 genes impair processes involved in repairing damaged DNA. People who carry particular disease-associated variants in these genes have a higher risk of developing breast, ovarian, and certain other cancers than people without those variants.
Other genetic variants can cause conditions directly. Sickle cell disease, for instance, results from disease-causing variants in the HBB gene, which provides instructions for making part of hemoglobin, the protein that carries oxygen in red blood cells.
Yet genes rarely operate in isolation. A genetic predisposition may increase the likelihood of a condition without guaranteeing that it will occur. The extent of that influence depends on the specific variant, the condition involved, other genes, and sometimes environmental or lifestyle factors.
What a genetic test can reveal about disease risk
One of the most important uses of genetic testing is identifying inherited susceptibility to disease. These tests can sometimes uncover meaningful risks before symptoms appear, giving patients and clinicians an opportunity to consider preventive measures, earlier screening, or other changes in medical care.
The information a test provides depends on the type of genetic variant it examines and how strongly that variant is associated with a particular condition.
Inherited cancer risk
Some genetic variants substantially increase the risk of developing certain cancers. In addition to BRCA1 and BRCA2, inherited variants in genes such as MLH1, MSH2, MSH6, and PMS2 can cause Lynch syndrome, a condition associated with increased risks of colorectal and endometrial cancers, among others.
A person who carries a clinically significant variant associated with inherited cancer susceptibility may benefit from screening that begins earlier or occurs more frequently than standard recommendations. Depending on the gene and the individual’s circumstances, preventive medication or surgery may also be considered.
A positive result does not mean cancer is inevitable. It indicates that the person’s risk differs from that of someone without the variant. The size of that difference varies by gene, variant, family history, and other factors.
Genetic testing can also help explain why certain cancers appear repeatedly in a family or occur at unusually young ages. However, most cancers are not caused by a single inherited variant. Many arise from genetic changes acquired in cells during a person’s lifetime, sometimes influenced by exposures, aging, and biological chance.
A tumor’s DNA can be tested to identify changes that may guide treatment. This is different from testing DNA inherited from a person’s parents: a variant found in a tumor may exist only in the cancer cells and may not be passed to children.
Heart disease and inherited cholesterol disorders
Genetic testing can identify some inherited conditions that affect the heart and blood vessels. Familial hypercholesterolemia, for example, is often caused by variants in genes involved in clearing low-density lipoprotein (LDL) cholesterol from the bloodstream.
People with this condition can have very high LDL cholesterol from an early age, increasing their risk of premature cardiovascular disease. Identifying the condition can prompt earlier treatment and testing of close relatives who may carry the same variant.
Other genetic conditions affect the heart muscle, electrical signaling, or structure of blood vessels. Some inherited forms of cardiomyopathy can weaken or enlarge the heart, while certain channel disorders can disrupt the electrical activity that controls heart rhythm.
In these cases, genetic information can help clarify a diagnosis, inform monitoring, and identify relatives who may need evaluation. A negative genetic test does not rule out every inherited heart condition, because not all disease-causing variants are known or detectable by a particular test.
Neurological and other inherited disorders
Genetic testing can also identify variants associated with conditions that affect the brain, nerves, muscles, and other organs.
Some inherited disorders cause symptoms during childhood, while others emerge in adulthood. Huntington disease, for example, is associated with an expansion of repeated DNA sequences in the HTT gene. In people who carry a disease-causing expansion, the condition can lead to progressive changes in movement, thinking, and behavior.
Other genetic tests can help diagnose conditions such as certain forms of muscular dystrophy, inherited retinal disease, or cystic fibrosis. In these situations, testing may explain symptoms, help establish a diagnosis, clarify how a condition is inherited, and guide decisions about treatment or supportive care.
The usefulness of testing varies by condition. Some genetic diagnoses have treatments that can alter the course of disease, while others primarily help families understand what to expect, plan care, or access appropriate support.
What a DNA test says about your future health
A central concept in genetics is the difference between having a genetic risk and developing a disease.
Some variants are associated with a high likelihood of disease under particular circumstances. Others produce only a modest increase in risk. Still others influence risk in ways that are difficult to interpret for an individual.
Penetrance describes how often people with a particular genetic variant develop the associated condition. A variant with high penetrance is more likely to produce the condition than one with low penetrance, although the exact relationship depends on the variant and the population being studied.
Variable expressivity describes differences in how a condition appears among people who have the same disease-associated variant. One person may experience relatively mild symptoms, while another develops more severe complications.
These distinctions explain why two people with the same inherited variant may have different medical experiences. Genetic testing can identify a risk factor without precisely predicting when a disease will begin, how severe it will become, or whether it will develop at all.
Risk estimates also depend on the strength of the evidence linking a variant to a condition. A well-established disease-causing variant in a gene with a clear relationship to a disorder provides different information from a variant that has only a weak or uncertain association.
For that reason, genetic results should be interpreted alongside personal medical history, family history, age, existing test results, and other relevant factors. A DNA test is most informative when it answers a specific clinical question rather than being treated as a complete forecast of future health.
Common types of genetic tests and what they measure
Not all DNA tests examine the same parts of the genome or answer the same questions. Some focus on a single gene, while others analyze many genes or much larger portions of a person’s DNA.
A targeted genetic test examines a particular variant or a defined set of variants. It may be appropriate when a family is known to carry a specific disease-associated variant or when a clinician suspects a particular inherited condition.
A multigene panel examines several genes associated with a disease or group of related conditions. For example, a hereditary cancer panel may analyze multiple genes involved in DNA repair and cell growth. Panels can be useful when different genes can produce similar symptoms or patterns of disease.
Exome sequencing analyzes most of the protein-coding regions of the genome. Because many known disease-causing variants occur in these regions, exome sequencing can help investigate unexplained or suspected genetic disorders, particularly when a more targeted test has not produced an answer.
Whole-genome sequencing examines DNA across the genome, including coding and noncoding regions. It can detect a broader range of genetic differences than some targeted approaches, but broader analysis does not guarantee that a test will explain a person’s symptoms or predict future disease. Some types of DNA changes are also harder to detect or interpret than others, depending on the technology and analysis methods used.
Genetic testing is not the same as measuring gene activity. Most routine DNA tests examine the sequence of genetic material, not whether a gene is currently switched on or how much of its product a cell makes. Other laboratory techniques can examine gene expression or related biological processes, but they answer different questions.
The best test is therefore not necessarily the one that analyzes the most DNA. It is the one suited to the medical question, with results that can be interpreted reliably.
How genetic testing differs from ancestry and direct-to-consumer DNA tests
Many people first encounter DNA testing through commercial services that provide ancestry estimates, information about genetic relatives, or selected health-related traits.
Ancestry testing generally examines genetic markers that can be compared with reference populations. These comparisons can suggest broad patterns of geographic ancestry or help identify genetic relationships. They do not provide a complete account of a person’s family history, cultural identity, or medical risk.
Some consumer tests also report health-related findings. These may include selected variants associated with inherited conditions, carrier status, medication response, or traits such as how a person metabolizes caffeine.
However, consumer tests vary in what they analyze and how their results are reported. Some examine only a limited selection of variants rather than comprehensively assessing the relevant genes. A test that does not detect a particular variant may therefore fail to identify a risk that a clinical test would find.
A consumer result suggesting increased risk should not automatically be treated as a medical diagnosis. Depending on the finding, a healthcare professional may recommend confirmation using a clinically appropriate test before making decisions about treatment, screening, or preventive surgery.
The same caution applies to reassuring results. A report showing no detected variants among those tested does not mean a person has no inherited health risks. It means that the test did not identify the particular findings it was designed and able to detect.
Direct-to-consumer testing can provide useful information, but its limitations matter most when results could influence important medical decisions.
Can genetic testing explain how you respond to medication?
Some genetic variants affect the enzymes, transporters, or other proteins that determine how the body processes medications. Testing for these differences is known as pharmacogenetic testing.
The liver, for example, uses enzymes to break down many drugs. Variants in genes that encode these enzymes can cause people to metabolize a medication more slowly or quickly than expected. Depending on the drug, this may affect how much medication remains in the bloodstream, whether it reaches an effective concentration, or whether side effects become more likely.
Other variants influence how a medication is activated, transported into cells, or recognized by its biological target. Genetic information can therefore help clinicians choose a medication, adjust a dose, or avoid a drug that may be unsuitable for a particular patient.
However, pharmacogenetic testing does not determine the perfect medication for every person. Drug response also depends on factors such as age, kidney and liver function, other medications, medical conditions, and the reason the drug is being prescribed.
Not every medication has a clinically useful genetic test, and the strength of evidence varies across drug-gene pairs. Results are most valuable when a particular genetic difference has a well-established effect on a treatment decision.
What carrier screening can tell you about inherited conditions
Carrier screening looks for genetic variants that can cause inherited conditions in children when particular combinations of variants are passed down from their biological parents.
A carrier often has one disease-associated copy of a gene and one working copy. For many recessive conditions, this is not enough to cause the condition in the carrier, although exceptions exist and the consequences depend on the specific disorder.
Cystic fibrosis and sickle cell disease are examples of conditions that commonly follow autosomal recessive inheritance. For a typical autosomal recessive condition, a child must inherit a disease-causing variant in both copies of the relevant gene to be affected.
If both biological parents carry a disease-causing variant in the same gene, each pregnancy generally has a one-in-four chance of resulting in a child with the condition, a one-in-two chance of resulting in a child who is a carrier, and a one-in-four chance of resulting in a child who inherits neither of those variants. These probabilities apply independently to each pregnancy.
Carrier screening can be performed before pregnancy or during pregnancy. If one person is found to carry a relevant variant, testing the other biological parent may help clarify the chance of having an affected child.
Screening cannot identify every possible disease-causing variant, and a negative result reduces risk rather than eliminating it. The remaining risk depends on the condition, the test’s detection ability, and the likelihood that an undetected variant is present.
Some inherited conditions follow other patterns, including dominant inheritance, in which one disease-associated copy of a gene can be sufficient to cause disease. Genetic counseling can help explain these differences and the implications of particular results for family planning.
How genes and lifestyle work together
For many common conditions, including type 2 diabetes, high blood pressure, heart disease, and many forms of cancer, risk reflects the combined effects of numerous genetic variants and non-genetic influences.
A person may inherit several variants that each make a small contribution to disease risk. Researchers sometimes combine these effects into a polygenic risk score, which estimates genetic susceptibility based on many variants across the genome.
Unlike a test for a single, highly influential disease-causing variant, a polygenic risk score generally describes a statistical tendency rather than a direct diagnosis. Its usefulness depends on how well the score has been developed and validated for the population and outcome in question.
A score may help distinguish groups with different average levels of risk, but it cannot reliably predict an individual’s future with certainty. The same score may not perform equally well across populations because genetic studies have not represented all ancestry groups equally, and genetic associations can vary between populations.
Non-genetic influences remain important. Diet, physical activity, tobacco exposure, sleep, infections, environmental conditions, and access to healthcare can all affect the development or progression of disease, depending on the condition.
Having a higher inherited risk does not make preventive measures pointless. In some circumstances, it makes prevention and screening more important. Conversely, a lower genetic risk does not make unhealthy exposures harmless or remove the need for routine preventive care.
Genes influence biological possibilities and probabilities. They do not operate as a fixed script for a person’s health.
What genetic test results mean
Genetic test reports commonly classify variants according to the strength of the evidence linking them to disease. In clinical genetics, five broad categories are often used: benign, likely benign, uncertain significance, likely pathogenic, and pathogenic.
A benign variant is not considered to cause the condition being evaluated. A likely benign variant is also thought not to be disease-causing, although the evidence may be less conclusive.
A pathogenic variant has sufficient evidence supporting a disease-causing role. A likely pathogenic variant has strong evidence of a disease-causing effect, but some uncertainty remains. The medical implications of either finding depend on the gene, the condition, and the person’s circumstances.
A variant of uncertain significance, often abbreviated VUS, is a genetic difference for which available evidence is insufficient to determine whether it causes disease. It is not the same as a positive diagnosis.
An uncertain result can be frustrating, especially when testing was prompted by a serious family history. However, acting on a VUS as though it were a confirmed disease-causing variant can lead to unnecessary worry, screening, or medical procedures. Clinicians generally base major management decisions on established risk factors and validated findings rather than an uncertain variant alone.
Interpretations can change as researchers gather more evidence. A variant initially classified as uncertain may later be considered benign or pathogenic. For some patients, a laboratory or clinical genetics team may recommend periodic review of results, particularly when the findings could affect care.
Genetic testing can also produce a negative result, but the meaning of a negative result depends on why the test was ordered. If a specific familial variant was known and the test reliably excludes it, the result may substantially clarify the person’s risk from that variant. If testing was broad or exploratory, a negative result may simply mean that no explanation was found with the methods used.
The limitations and uncertainties of DNA testing
Genetic testing has become increasingly capable, but several important limitations remain.
First, not all disease-causing variants are known. Scientific understanding of many genes is incomplete, and some genetic changes have effects that are difficult to establish. A test may identify a variant without revealing what it means for health, or it may miss a variant that contributes to disease.
Second, different testing methods detect different kinds of genetic changes. Some tests are designed to find single-letter substitutions, while others are better suited to identifying missing or duplicated sections of DNA, repeated sequences, or complex structural changes. A test’s ability to detect a variant depends on the technology, the regions examined, and the laboratory’s analysis.
Third, a genetic result may have limited predictive value even when the variant is real and its biological effect is understood. A risk estimate derived from a group of people does not specify exactly what will happen to one individual. Age, other genes, environmental exposures, and factors not yet understood can alter the outcome.
Fourth, genetic findings can have implications beyond the person being tested. Because biological relatives share portions of their DNA, one person’s result may reveal information about a parent’s, sibling’s, or child’s potential risk. This can be medically useful, but it can also raise difficult questions about when and how to share results.
Genetic information is also sensitive personal information. Before using a testing service, it is worth understanding how samples and data are stored, whether information may be shared with research partners or other organizations, whether samples may be retained, and what options exist for withdrawing consent or requesting deletion. The protections and practical limits vary by service and legal context.
In the United States, the Genetic Information Nondiscrimination Act generally restricts the use of genetic information by health insurers and employers in specified circumstances. It does not provide the same protections for every form of insurance, including life, disability, and long-term care insurance. State laws and other federal rules may offer additional protections, but their scope varies.
These considerations do not make genetic testing inherently unsafe or unhelpful. They highlight why people should understand the purpose of a test and the possible consequences of its results before proceeding.
When genetic testing may be useful
Genetic testing is especially useful when it addresses a defined medical question and the answer could change care.
A clinician may recommend testing when a person develops symptoms suggestive of an inherited disorder, has a close relative with a known disease-causing variant, or has a personal or family history that raises concern about inherited cancer or heart disease. Testing may also be considered when a condition appears unusually early, several relatives have similar diagnoses, or a medication decision could be influenced by genetic information.
In some cases, genetic testing is appropriate even when someone feels healthy. A person with a known familial variant may benefit from learning whether they carry it before symptoms emerge. Carrier screening may provide information relevant to reproductive decisions, while certain pharmacogenetic tests may help guide medication choices.
Not everyone needs broad genetic testing. For many people, routine medical history, family history, blood pressure measurements, cholesterol testing, blood glucose testing, and age-appropriate screening provide more immediately actionable information than a general DNA test.
A healthcare professional can help determine whether testing is appropriate, which test best addresses the question, and what different results could mean. Genetic counselors are trained to explain inherited risks, discuss testing options, and help people understand the medical and family implications of the findings.
The value of a test depends not simply on how much genetic information it produces, but on whether that information is accurate, interpretable, and useful for a person’s decisions.
How to use genetic information to make health decisions
A genetic result should be considered one part of a broader medical assessment. Before testing, it helps to identify the question the test is intended to answer: whether a particular inherited condition may explain symptoms, whether an established familial variant is present, whether a medication might be affected by genetics, or whether inherited risk warrants a different screening strategy.
After testing, the next step is to understand what the result does and does not establish. A confirmed disease-causing variant may support a specific prevention or monitoring plan. An uncertain variant may require further evidence rather than immediate action. A negative result may be reassuring in some circumstances but leave meaningful risk unresolved in others.
Family history remains important, even when genetic testing is negative. A strong pattern of disease among close relatives can indicate elevated risk that current testing cannot fully explain. Similarly, a person without a notable family history can still carry an inherited variant, because some conditions are uncommon, family size may be small, or relatives may not have lived long enough to develop symptoms.
The most useful response to genetic information is not to assume the future is predetermined, nor to dismiss a result because it describes only a probability. It is to use the evidence appropriately, in consultation with qualified healthcare professionals, to make decisions that reflect the individual’s circumstances.
A DNA test can reveal important clues about inherited disease, medication response, and reproductive risk. Its greatest value lies in connecting those clues to sound medical interpretation and practical action. It can help explain why a condition develops, identify risks before symptoms appear, or guide more personalized care—but it cannot tell the whole story of a person’s health.