Pharmacogenetics in Preventive Health

How genes can influence your response to medications

Prescribing a medication can look straightforward on paper. In reality, the decision about which drug to use and at what dose is shaped by many factors. Prescribing clinicians consider multiple factors, including the condition being treated, a person’s age and weight, other medications, kidney and liver function, past side effects, and patient preferences.

One important factor that can be overlooked is how a person’s body is biologically set up to process a medication, which is largely determined by genetics.

Pharmacogenetics looks at how inherited genetic differences can affect the way people respond to certain medications. While it does not assess disease risk or determine whether someone should take a medication, pharmacogenetic testing adds valuable information to support medication and dosing decisions.

“For many people, the benefit of pharmacogenetic testing is simply understanding a bit more about how their body may process certain medications,” says Jill Furnival, a certified genetic counsellor from the NiaHealth clinical team. “It’s information that can be helpful for current or future medication decisions.”

How genetics influences medication response

When a person takes a medication, several biological steps follow. The drug must be absorbed, reach its target, exert its effect, and then be broken down and cleared from the body. Many of these steps involve enzymes, particularly in the liver.

Genes provide the instructions for making these enzymes. Differences in our genes can affect how well those enzymes work.

This means that genetic differences can influence how quickly or slowly a drug is processed. Some people metabolize certain medications more quickly, while others do so more slowly. These differences can affect whether a standard dose works as intended or increases the risk of side effects.

“If you break down a drug too quickly, it may not stay in your system long enough to do its job,” Furnival explains, “If you break it down too slowly, it can build up in your system and increase the risk of side effects. It’s a simplified explanation, but it helps show why the same medication can work well for one person and not for another.”

Medication response is always influenced by many factors. Age, other medications, organ function, inflammation, and lifestyle choices such as smoking all matter. Pharmacogenetics focuses on one part of this bigger picture: genes involved in drug metabolism, transport, and response.

How the test works

Pharmacogenetic testing is a DNA test. It uses a cheek swab or blood sample that is sent to a laboratory. The lab extracts DNA from the sample and analyzes genes involved in how medications are processed.

The laboratory then applies this genetic information across a panel of commonly used medications. For each medication on the panel, the report describes how a person is likely to process that medication based on their genetics.

Results are grouped into metabolizer categories, including poor, intermediate, and normal. These terms describe how quickly or slowly a medication is likely to be processed. For example, a “poor” metabolizer may break down a medication more slowly than expected, while a “normal” metabolizer processes it at a typical rate.

This information should not be used on its own to prescribe a medication or dose. Instead, it complements clinical history, lab results, and patient preferences.

A support tool, not a prescription

One of the most important things to understand about pharmacogenetics is what it does not do.

Pharmacogenetic testing cannot predict with certainty whether a medication will work. Prescribing providers still consider many factors, including diagnosis, lab results, medical history, potential drug interactions, and a person’s preferences. Medication decisions are always made based on the full clinical picture.

“Pharmacogenetics is a decision-support tool,” Furnival emphasizes, “It can offer a better starting point, but it never replaces the role of the prescribing provider.”

Used appropriately, pharmacogenetics can help flag medications that may benefit from closer monitoring, dose adjustment, or a different approach. Its value lies in helping reduce unnecessary trial and error. Time spent on medications that are not effective, or managing avoidable side effects, can affect quality of life and delay symptom improvement.

Importantly, pharmacogenetic results do not mean a medication should be changed if it is working well and not causing side effects. Many people take medications that are effective and well-tolerated, even when genetics suggest an alternative might be considered in other situations. Any decision to change a medication should always be made together with a prescribing provider.

Why pharmacogenetics fits into preventive care

Pharmacogenetics is often used when a specific medication is being prescribed for a specific condition. In oncology, for example, testing may be required to reduce the risk of severe toxicity from certain chemotherapies. For medications like warfarin, genetic information can help guide safer dosing.

In preventive care, the value looks different.

Most people will need prescription medications at some point in their lives. In 2021, more than two-thirds of Canadians reported taking or being prescribed at least one medication in the previous year. Having pharmacogenetic information already on record can be helpful when new medication decisions arise.

As Furnival points out, “You never know when you will need medication, having this information available means your prescribing provider has more to work with when deciding on a medication or dose.”

For example, some commonly used pain medications, such as codeine, need to be converted into an active form by the body to work properly. Genetic differences can influence how efficiently that happens. Knowing this in advance can help a prescriber consider alternatives if a medication is less likely to be effective or well-tolerated.

A person’s genes do not change over time; therefore, the underlying genetic information remains relevant long-term. At the same time, scientific knowledge continues to evolve. New gene–drug pairs are identified, guidelines are updated, and testing panels expand.

For this reason, NiaHealth avoids describing pharmacogenetic testing as a one-time test. The DNA is stable, but interpretation is not. Results may be reinterpreted over time as evidence evolves, and in some cases, additional testing may become useful.

To support this, NiaHealth has partnered with a testing provider that actively monitors the science and updates interpretations as new evidence becomes available.

What is a gene–drug pair?

A gene–drug pair refers to a specific gene and a specific medication where genetic differences are known to affect how that medication is processed or how it works in the body.

Why panel quality matters

Pharmacogenetic testing is well supported by high-quality peer-reviewed evidence. However, not every gene–drug pair is equally strong.

Test panels vary widely. Some focus on a single therapeutic area, such as mental health medications, while others span multiple domains. Panels also differ in the strength and consistency of evidence behind the gene–drug pairs they include.

When we reviewed our testing partner’s standard pharmacogenetics panel, we did not accept it at face value. We assessed each gene and evaluated the strength and consistency of evidence behind every gene–drug pair using established, peer-reviewed resources.

At NiaHealth, panel selection prioritizes clinical validity and actionability. We selected a Canadian-based provider with validated laboratory processes and strong privacy protections, then curated a focused set of high-evidence gene–drug pairs. These are the findings shown on the NiaHealth dashboard.

While members have access to their full pharmacogenetics laboratory report, the dashboard highlights the results most likely to be useful and actionable in preventive care.

How results are used at NiaHealth

Once testing is complete, results are integrated into the NiaHealth platform to support informed, evidence-based conversations about medications.

For members, this information can become relevant in many common situations. Some people learn that they may process certain antidepressants differently, which can help inform medication choice or dosing if treatment is being considered. Others gain insight into how they may respond to common pain medications, acid reflux treatments, or statins when used at higher doses.

For example, someone who has an increased risk of cardiovascular disease and is discussing options for cholesterol-lowering medications–such as statins–with their primary care provider may find it helpful to already have pharmacogenetic information on hand. If a statin is being considered, these results can help inform conversations about expected response or tolerance.

A member’s medications and health history are reviewed to identify findings that may be relevant now or in the future. Members then discuss their results in a one-on-one session with a certified genetic counsellor, who explains what the findings mean and where their limits lie.

Jill Furnival adds, “Too often, pharmacogenetic reports are filed away and never revisited. Our role is to help you understand your results and support you in sharing them with your primary care provider or other prescribing clinicians when needed.”

Results are presented in a clear, colour-coded format in the NiaHealth dashboard to support understanding. A result flagged for caution does not mean that a medication should be discontinued, particularly if it is effective and well-tolerated. Instead, it can provide an opportunity for discussion and planning for future medication decisions. Members can also download a copy of their full report for their records or to share with other healthcare providers.

NiaHealth does not prescribe medications. Our role is to support understanding and informed conversations, while clinical decisions remain with the appropriate prescribing provider.

The bottom line

Pharmacogenetic testing does not replace discussions with a healthcare provider and careful professional input. What it can do is add an important layer of insight that helps people understand their options and ask better questions when medication decisions arise.

This combination of strong evidence, clear clinical actionability, and long-term relevance is why pharmacogenetics was the first genetic test we added to our preventive care program.

Used thoughtfully, it becomes a resource that can be revisited as evidence evolves and new medication decisions arise, supporting safer and more personalized care over time.

Pharmacogenetics vs pharmacogenomics‍

You may also hear this testing referred to as pharmacogenomics. While the terms are closely related and sometimes used interchangeably, there is a distinction.

Pharmacogenetics traditionally focuses on how variation in specific genes affects response to specific medications. Pharmacogenomics is a broader term that can include genome-wide influences and larger data models.

NiaHealth uses the term pharmacogenetics to reflect a targeted, evidence-informed approach focused on gene–drug pairs with clear clinical relevance today.