What your DNA file says about how you handle medicines
Of everything that can be read from a consumer DNA file, this is the part with the clearest practical use — and the part most people never see, because the services that sold them the test do not report it.
What is pharmacogenomics?
Pharmacogenomics is the study of how inherited differences change the way people process medicines. Some people clear a drug quickly and some slowly, so the same standard dose can behave differently in different bodies. Several of the genes involved are well studied, and markers for them sit in ordinary consumer DNA files.
The practical version: a prescriber picks a starting dose from what works for most people. For most people that is right. For a minority it is too much or too little, and the reason is often inherited.
We read these markers against the guidelines published by CPIC — the consortium of pharmacologists who write the dosing standards themselves. Those guidelines are peer-reviewed, freely published, and written to be acted on. This is the one area where free, open sources deliver something genuinely comparable to a paid product.
Which medicines can a consumer DNA file say something about?
Eight gene groups are well covered by consumer arrays, and between them they touch blood thinners, antidepressants, stomach-acid drugs, statins, immune-suppressing medicines, two families of chemotherapy, some antibiotics and anti-malarials, and the anti-rejection medicines given after a transplant. Two further genes are listed below because we cannot read them, which matters just as much.
| What we look at | Markers | Coverage |
|---|---|---|
| Blood thinners, antidepressants and stomach-acid drugs | CYP2C19 | Read from your file |
| Warfarin, a common blood thinner | CYP2C9, VKORC1 | Read from your file |
| Statins, and muscle pain from them | SLCO1B1 | Read from your file |
| Medicines that damp down the immune system | TPMT, NUDT15 | Read from your file |
| Some chemotherapy medicines | DPYD | Read from your file |
| A chemotherapy medicine, and jaundice | UGT1A1 | Read from your file |
| Some antibiotics and anti-malaria medicines | G6PD | Read from your file |
| Anti-rejection medicines after a transplant | CYP3A5 | Read from your file |
| Codeine and many antidepressants | CYP2D6 | Not readable from array data |
| Severe allergic reactions to certain medicines | HLA-B | Not readable from array data |
The point of the list is not that any of these will apply to you. It is that if one of them is ever prescribed, the information was sitting in a file you already owned.
What can a consumer DNA file not tell you about medicines?
Two important ones. CYP2D6 — codeine and many antidepressants — needs copy-number calling that genotyping arrays cannot do reliably. HLA-B, which relates to severe reactions to certain medicines, is poorly covered by the markers on these chips. We report both as unreadable rather than typical.
This distinction is the whole reason to trust or distrust a report of this kind. An absent reading and a normal reading look identical if a service chooses to present them the same way, and presenting a gap as a clean result is the most consequential thing a report like this can get wrong.
So the rule we hold to is simple: where your file has no usable marker, the report says so.
Should I change my medication because of a DNA report?
No. Never stop, start or change a dose on the basis of any report, including ours. What this is useful for is a conversation: taking the finding to the person writing your prescription, who can weigh it against everything else they know about you, and order clinical testing if it matters.
Pharmacogenomic results are one input among many — age, kidney and liver function, other medicines, and what has actually worked for you before all matter, and a prescriber sees all of them. Nothing here is a diagnosis, and none of it replaces a conversation with a clinician who knows your history.
The other categories
- Family planning What being a carrier means, which recessive conditions a consumer DNA file covers, and why a clear result is not an all-clear.
- Nutrition Which nutrition and wellness markers a consumer DNA file covers, how strong the evidence behind them is, and why a blood test still beats a genotype.
- Fitness What a consumer DNA file can suggest about power versus endurance, response to training, injury predisposition and recovery — and the limits of all four.
- Traits Which everyday traits can be read from a consumer DNA file, which of them rest on strong single-gene evidence, and which are much weaker than they look.
- Ancestry How an ancestry breakdown is computed from a consumer DNA file, what mtDNA and Y haplogroups add, and why two services reading the same file disagree.