What Can Your Genes Really Tell You About Your Health?

A cheek swab can reveal information that once required a specialist appointment and a laboratory. From ancestry to inherited traits and health-related variants, genetic testing has moved firmly into everyday life.

That accessibility brings an obvious question: how much can a person’s genes really reveal about their health?

The answer is more nuanced than a DNA report might suggest. Genetic information can identify variants and illuminate biological differences, but most health outcomes are shaped by far more than genes alone. Age, family history, environment, lifestyle and other biological factors all contribute.

Genes can provide useful context. They rarely provide a forecast.

What Does a Genetic Test Actually Measure?

The human genome contains around 3.2 billion DNA letters and approximately 20,000 genes (Genomics England, n.d.). Yet most genetic tests examine only a fraction of that information.

The amount examined depends on the type of test. Some clinical tests sequence a particular gene or group of genes. Whole-genome sequencing attempts to read almost all of a person’s DNA.

Most direct-to-consumer tests take a different approach. They use genotyping chips to examine hundreds of thousands of pre-selected single-nucleotide polymorphisms, or SNPs: positions in DNA where people commonly differ (McPherson, 2020).

That distinction matters. SNP arrays are useful for detecting the variants they were designed to examine, but they don’t sequence every letter in a gene and can’t rule out every potentially significant variant. NHS genomic guidance specifically warns that some consumer tests can therefore produce false reassurance when only a limited number of variants have been checked (NHS England Genomics Education Programme, 2023).

One Gene Can Mean Different Things

Targeted tests can still answer clearly defined genetic questions.

Readers exploring genetic testing can try Fenix Health Science products to see how a consumer report may focus on identifying a specific APOE genotype rather than attempting to provide a complete picture of a person’s health. 

APOE also illustrates why genetic results require context.

The gene has several common variants, including APOE ε2, ε3 and ε4. APOE ε4 is associated with a higher likelihood of developing late-onset Alzheimer’s disease, but it is a risk factor rather than a diagnosis. Some people who inherit APOE ε4 never develop Alzheimer’s, while many people who develop the condition don’t carry ε4 (MedlinePlus Genetics, n.d.).

For that reason, APOE risk testing isn’t routinely offered by the NHS simply to predict whether an asymptomatic person will develop Alzheimer’s in the future. Testing can have other clinical or research uses, but knowing APOE status alone can’t determine an individual outcome (Alzheimer’s Research UK, 2025).

Risk Isn’t Destiny

APOE is just one example of a wider principle.

A small number of inherited conditions are strongly associated with changes in a single gene. Most common health conditions are considerably more complicated. They are polygenic and multifactorial, meaning that many genetic variants may contribute alongside non-genetic factors.

Polygenic risk scores, or PRS, attempt to capture some of that complexity. Instead of examining one variant, they combine the effects of many genetic differences into an estimate of inherited susceptibility.

The science is promising, but interpretation is still evolving.

Clinical studies are now investigating how PRS might complement existing risk assessments, but important questions remain about clinical utility, communication and how results should influence care (Lennon et al., 2024). A score shouldn’t be viewed as a stand-alone prediction of what will happen to one person.

There is another problem: ancestry.

Many of the genome-wide studies used to construct risk scores have historically included disproportionately large numbers of people with European genetic ancestry. Scores developed using one population can perform less accurately when applied to another (Ge et al., 2024).

Genetic risk may look like a precise number on a screen. The science underneath that number can be considerably less precise.

Clinical and Consumer Testing Answer Different Questions

Clinical genomic testing generally starts with a medical question.

A clinician may investigate a known variant in a family, examine a gene associated with particular symptoms or recommend a broader test when several possible explanations need to be considered. Genetic counselling can also help people understand what the results could mean for them and their relatives (NHS, n.d.).

Consumer testing begins with the individual instead.

That makes access easier, but removes some of the clinical context that normally surrounds genetic testing. Professor Anneke Lucassen, a clinical geneticist at the University of Southampton, has cautioned that consumer tests “should absolutely not be used to inform health decisions without further scrutiny” (McPherson, 2020).

A consumer result can therefore be useful information without necessarily being the final answer.

Four Questions to Ask Before Taking a Genetic Test

A few questions can make genetic information much easier to interpret.

What is actually being tested? A targeted genotype, SNP array, gene panel and whole-genome sequence provide very different amounts of information.

What can a negative result rule out? If a test examines only selected variants, “nothing found” doesn’t necessarily mean that every relevant genetic variant has been excluded.

Who can explain an unexpected result? A genetic counsellor or appropriately qualified healthcare professional can place findings alongside family history and other relevant information.

What happens to the genetic data? Sample storage, secondary research use, third-party sharing and deletion policies all deserve attention.

The last question is particularly important because DNA isn’t ordinary personal information. It is permanent and partly shared with biological relatives. The UK Government Office for Science has noted that genomic data can potentially be used to infer the identity of an individual or a close relative, making genuine anonymity difficult to guarantee (Government Office for Science, 2022).

What About Genetic Tests and Insurance?

Concerns about insurance can also make people hesitant about testing.

In the UK, the Code on Genetic Testing and Insurance distinguishes between diagnostic results and predictive genetic results.

Insurers signed up to the Code can’t require someone to take a genetic test and generally can’t request or use predictive genetic test results. The current financial thresholds are £500,000 for life insurance, £300,000 for critical illness cover and £30,000 per year for income protection (Department of Health and Social Care, 2026).

Importantly, those thresholds don’t mean insurers can currently request any predictive test above them. As of the March 2026 update, the only approved exception is a predictive test for Huntington’s disease when an application for life insurance exceeds £500,000. There are currently no approved predictive-test exceptions for critical illness or income protection insurance (Department of Health and Social Care, 2026).

Conclusion

Genetic testing can reveal genuinely useful information. It can identify specific variants, clarify inherited patterns and provide another piece of biological context.

What it can’t usually do is read the future.

A genetic association isn’t automatically a diagnosis, a high-risk result isn’t a certainty and a reassuring result may not exclude every relevant variant. Even sophisticated polygenic scores still sit alongside family history, lifestyle, environment and other health information.

The most useful question may therefore be less dramatic than “What does the DNA say will happen?”

It’s simply: “What does this particular result tell someone — and what does it leave unanswered?”

Understanding that distinction is what turns genetic data into genuinely useful information.

References

Alzheimer’s Research UK. (2025). APOE4 gene. Alzheimer’s Research UK.

Department of Health and Social Care. (2026, March 19). Code on genetic testing and insurance. GOV.UK.

Ge, T., Irvin, M. R., Patki, A., et al. (2024). Principles and methods for transferring polygenic risk scores across global populations. Nature Reviews Genetics, 25, 8–25.

Genomics England. (n.d.). Understanding genomics. Genomics England.

Government Office for Science. (2022, January 26). Genomics beyond health. GOV.UK.

Lennon, N. J., Kottyan, L. C., Kachulis, C., et al. (2024). Selection, optimisation and validation of ten polygenic risk scores for clinical implementation in diverse US populations. Nature Medicine, 30, 480–487. https://doi.org/10.1038/s41591-024-02796-z

McPherson, A. (2020, January 15). Consumer genetic testing: Expectation and reality. NHS Genomics Education Programme.

MedlinePlus Genetics. (n.d.). Alzheimer’s disease. U.S. National Library of Medicine.

NHS. (n.d.). Genetic and genomic testing. National Health Service.

NHS England Genomics Education Programme. (2023). Direct-to-consumer constitutional (germline) genomic testing. GeNotes Knowledge Hub.