Genetic Testing for Health: What It Can Tell You, Its Limits and Privacy Risks

By Dr. Ande Sriman, M.B.B.S., M.D., Fellowship in Diabetes Mellitus
Consultant Physician and Panel Member of Medicine and Science, 150.fit

Your DNA can reveal important information about health risk. But genetic risk is not the same as your future. Patients considering genetic testing often ask me some version of the same question: “If something is written in my DNA, does that mean it is going to happen?” The answer is usually more nuanced. Genetic testing can identify inherited variants associated with certain diseases, provide information about how some medicines may affect you, and help estimate susceptibility to complex conditions.

But a genetic result rarely tells the entire story. Your health is shaped by an interaction between genetics, environment, lifestyle, ageing, medical history and chance. Genetic information is therefore most useful when it is interpreted in the context of the individual rather than treated as a prediction of destiny.

What Is Genetic Testing for Health?

Genetic testing examines DNA for variations that may have implications for health. Depending on the type of test, it can help identify an inherited condition, estimate increased susceptibility to certain diseases, provide information relevant to medication response, or determine whether someone carries a genetic variant that could be passed to their children.

But “genetic testing” is not one single test.Testing may range from analysis of one specific gene to a multi-gene panel, whole-exome sequencing or whole-genome sequencing. Direct-to-consumer tests may examine a much narrower set of variants and answer very different questions from clinical genetic testing.

What Can Genetic Testing Tell You About Your Health?

1. It Can Identify Some High-Impact Inherited Disease Risks

Some diseases are strongly associated with pathogenic variants in individual genes. For example, inherited harmful variants in BRCA1 or BRCA2 significantly increase the risk of breast, ovarian and several other cancers. Knowing that such a variant is present can influence recommendations around surveillance and preventive care. Another example is familial hypercholesterolaemia, an inherited disorder in which genetic variants can lead to very high LDL cholesterol and increased cardiovascular risk from an early age. These are very different from the small genetic effects involved in most common chronic diseases. When a clinically significant single-gene variant is found, the result may have implications not only for the individual but also for biological relatives.

2. Pharmacogenomics Can Help Explain Differences in Medication Response

Pharmacogenomics, or PGx, studies how genetic variation affects the way people respond to medicines. One well-established example involves clopidogrel, an antiplatelet medication. People with certain CYP2C19 variants produce less of the active form of clopidogrel. Clinical pharmacogenomic guidelines therefore recommend considering alternative antiplatelet therapies for some intermediate and poor metabolisers, particularly in relevant cardiovascular settings such as acute coronary syndrome or PCI. Genetic variation can also influence the risk of muscle-related adverse effects from certain statins. Variants involving SLCO1B1, for example, can influence statin exposure and may inform drug or dose selection in appropriate patients. Pharmacogenomic testing does not tell a physician what to prescribe in isolation. Age, kidney and liver function, other medications, diagnosis and clinical guidelines still matter.

3. Polygenic Risk Scores Can Estimate Susceptibility to Complex Diseases

Many common conditions are not caused by a single genetic variant. Diseases such as coronary artery disease and type 2 diabetes involve the combined effects of many genetic variants together with lifestyle and environmental factors. A polygenic risk score, or PRS, combines information from multiple genomic variants into a statistical estimate of genetic susceptibility. Importantly, a PRS reflects genetic risk only. It does not automatically account for diet, exercise, smoking, blood pressure, environment or other clinical factors. And a high score does not mean that disease is inevitable.

Why Ancestry Matters in Genetic Risk Scores

This is an especially important limitation of polygenic risk scores. Many of the large datasets historically used to develop PRS models have disproportionately represented people of European ancestry. As a result, the accuracy of a score may change when it is applied to people whose ancestry differs from the population in which the model was developed. NIH researchers have specifically identified this as an important limitation and are working to improve PRS performance across more diverse populations.

For any genetic risk score, clinicians therefore need to understand which population the model was developed and validated in. A number without that context can create a false sense of precision.

What Genetic Testing Cannot Tell You

Genetic testing can provide valuable information, but it has important boundaries.

Genetic Risk Is Not Certainty

Having an inherited risk variant does not necessarily mean that you will develop the associated disease.For complex diseases, genes interact with many other factors. A well-known study of coronary artery disease, for example, found that among people with high genetic risk, a favourable lifestyle was associated with approximately 46% lower relative risk of coronary events compared with an unfavourable lifestyle. That finding supports the importance of lifestyle even in people with elevated genetic susceptibility—but it does not mean lifestyle universally “cancels out” a fixed percentage of genetic risk. That distinction is important. Your genes can influence risk without determining the outcome.

A Negative Result Does Not Mean Zero Risk

A genetic test that does not identify a pathogenic variant does not necessarily mean that a person cannot develop the disease. For example, only about 5–10% of cancers are thought to result from inherited harmful genetic changes. Many cancers develop through genetic changes acquired during life rather than variants inherited from a parent. The same principle applies more broadly: genetic testing is only one component of risk assessment. Family history, age, lifestyle, clinical biomarkers and established screening recommendations still matter.

Sometimes the Result Is Uncertain

Genomic testing may identify a variant of uncertain significance, or VUS.This means a genetic difference has been found, but current evidence is insufficient to determine whether it causes or contributes to disease. A VUS should generally not be treated as a disease-causing result or used on its own to make clinical decisions. Its classification may change as scientific evidence improves.

This is another reason professional interpretation matters.

Direct-to-Consumer Genetic Tests vs Clinical Genetic Testing

Not every DNA test provides the same depth or clinical value.

Some direct-to-consumer tests assess only a subset of known disease-associated variants. Therefore, a negative result may not rule out a clinically important variant. NHGRI notes that potentially actionable findings from DTC testing may also require confirmation with a clinical genetic test before they are used for medical decision-making. The FDA similarly advises that direct-to-consumer genetic test results should not be the sole basis for treatment or other medical decisions.

What Should You Ask Before Taking a Genetic Test?

Before testing, the most important question is not: “How much of my genome does this test analyse?”

It is: “What health question am I trying to answer, and will this test provide information I can meaningfully use?”

A broader test does not automatically mean a more useful test. The clinical value depends on the quality of the laboratory, which variants are analysed, how strongly they are associated with disease, the population in which the evidence was generated, and whether anything useful can be done with the result.

Genetic Testing and Privacy

Genomic data deserves special consideration because DNA is deeply personal, relatively permanent and partly shared with biological relatives. Before submitting a sample, understand how the testing provider handles your information. Questions worth reviewing include whether your sample will be retained, whether your genomic data may be used for research, whether it may be shared with third parties, how consent can be withdrawn, and whether your data or physical sample can later be deleted.

Privacy protections also differ according to country, healthcare system and whether testing occurs clinically or directly through a consumer company.

For example, in the United States, GINA protects against certain uses of genetic information in health insurance and employment, but those protections do not extend in the same way to life, disability or long-term-care insurance. HIPAA protections also apply in particular healthcare contexts rather than automatically covering every consumer genetics service.

For an international audience, the important principle is therefore: check the privacy policy and the genetic-information laws that apply where you live before testing.

Genetic Information Can Affect More Than One Person

A genetic test is unusual because the information it reveals may have implications for biological relatives. If testing identifies an inherited pathogenic variant, siblings, parents or children may also have a chance of carrying it. This is why genetic counselling can be particularly valuable before and after testing for hereditary disease. A genetic result is not simply another laboratory value—it can have medical, psychological and family implications.

How to Make Genetic Testing Clinically Useful

In precision medicine, genetic information is rarely interpreted on its own.Its value increases when it is considered alongside:

Family history + Medical history + Biomarkers + Lifestyle + Environment + Medications + Clinical Examination

Genetics can help explain susceptibility. It may indicate that screening should begin earlier, that a particular medicine deserves reconsideration, or that an inherited condition should be investigated more closely. But it should complement established clinical care rather than replace it.

References & Further Reading

• National Institutes of Health (NIH): The Promise of Precision Medicine
• Horvath, S. (2013): DNA methylation age of human tissues and cell types. Genome Biology, 14(10), R115.
• Lu, A. T., et al. (2019): DNA methylation GrimAge strongly predicts lifespan and healthspan. Aging (Albany NY), 11(2), 303–327.
• Belsky, D. W., et al. (2022): DunedinPACE, a DNA methylation biomarker of the pace of aging. eLife, 11, e73420.
• Ferrucci, L., et al. (2020): Measuring biological aging in humans: A roadmap. Journals of Gerontology: Series A, 75(8), 1502–1505.