Short answer: pharmacogenomic (PGx) testing looks at genes that affect how your body processes certain medications. It can flag when a drug may build up or clear too quickly, which can guide dosing or help explain side effects. It cannot predict with certainty which antidepressant will work, and it does not replace a careful clinical evaluation.
What the test measures
Most panels check liver enzyme genes (such as CYP2D6 and CYP2C19) that break down many antidepressants and other medications. People can be “poor,” “normal,” “rapid” or “ultrarapid” metabolizers.
When it may be useful
- You have had side effects from several medications at low doses
- Several medications have not worked at usual doses
- You take many medications and interactions are a concern
Limitations
- Genes are only one factor; diagnosis, other medications, age, smoking and adherence matter too
- Test reports sorting drugs into “green, yellow, red” can oversimplify
- Insurance coverage varies, and costs can be significant
How a psychiatrist uses results
Results are combined with your history and preferences to choose a medication and starting dose, and to decide how closely to monitor. They may also explain past experiences, which many patients find validating.
An example of how results are used
Suppose someone has had strong side effects from several antidepressants at low doses. A test might show they are a poor metabolizer for an enzyme that breaks down those medications, meaning the drugs build up to higher levels than expected. The psychiatrist might choose a medication processed by a different pathway, or start at a lower dose and increase slowly.
Interactions matter as much as genes
Some common medications can block the same enzymes measured on genetic tests, effectively changing how you metabolize other drugs. A careful review of all medications, including over-the-counter products, is just as important as genetic results.
What to ask before testing
- How will results change my treatment plan?
- Is the test covered by my insurance, and what will I pay?
- Who will explain the results to me?
Frequently asked questions
Do I need testing before starting an antidepressant?
Usually not. Most people start treatment without testing and do well.
Are results relevant for life?
Your genes do not change, so results can guide future prescribing across medicine.
Discuss whether testing makes sense for you at a medication management visit with Psych Boston. Request an appointment.
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This article is general information, not medical advice. If you are in crisis, call or text 988 or call 911. Psych Boston is an outpatient psychiatry practice at 35 Bedford St #17, Lexington, MA781-218-9550).