CYP1A2 rs762551: fast or slow caffeine metabolizer?
Ever wonder why one coffee keeps a friend up all night while you sleep fine after an espresso at dinner? A big part of the answer is CYP1A2 rs762551 — the variant that governs how fast your body clears caffeine. Here's what it means, how to find it in your 23andMe or AncestryDNA raw data, and what the fast/slow genotypes are associated with.
What CYP1A2 does
CYP1A2 is a liver enzyme responsible for metabolizing roughly 95% of the caffeine you consume. How active your version is determines how long caffeine — and its stimulant effects — stick around.
The rs762551 variant sits in the gene's regulatory region and is associated with how inducible (responsive) the enzyme is:
- A allele (the *1A version): associated with a fast, highly-inducible enzyme.
- C allele (the *1F version): associated with slower metabolism.
What the genotypes are associated with
| Genotype | Type | Associated tendency |
|---|---|---|
| AA | Fast metabolizer | Caffeine cleared quickly; often tolerates coffee later in the day |
| AC | Slower | Intermediate clearance |
| CC | Slow metabolizer | Caffeine lingers; effects (and jitters/sleep disruption) last longer |
Fast metabolizers often handle caffeine comfortably; slow metabolizers may feel it more strongly and longer. Some research also links slow metabolism + heavy coffee intake to modestly higher cardiovascular risk — but the evidence is mixed, and sleep, dose, and timing matter a lot.
How to find rs762551 in your raw data
- Download your raw data (or from AncestryDNA / MyHeritage).
- Search it for
rs762551and read your genotype. - Or use our free DNA explorer — it reads your file in your browser and shows this exact marker, with nothing uploaded.
Strand note: 23andMe usually reports rs762551 on the A/C strand. Some files use the opposite strand (T/G), which can flip how the letters look.
What it does and doesn't tell you
This is a genuinely useful, low-stakes marker — knowing it can help you time your coffee. But it's one variant among many, and it's not medical advice. If you have heart concerns or caffeine sensitivity, that's a conversation for a clinician, not a raw-data lookup.
For the full set of what's in your file, see our complete guide to analyzing 23andMe raw data, or browse the rest of the Quanome blog.
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Frequently asked questions
What does CYP1A2 rs762551 tell you?
CYP1A2 is the enzyme that breaks down about 95% of the caffeine you consume. The rs762551 variant is associated with how fast it works: the AA genotype is linked to faster caffeine metabolism, while AC and CC are linked to slower metabolism.
Which genotype is the fast caffeine metabolizer?
AA (sometimes written as the *1A/*1A 'fast' type) is associated with faster caffeine clearance. AC and CC carry the slower-inducible C allele and are associated with caffeine lingering longer in the body.
How do I find CYP1A2 in my raw data?
Search your raw DNA file for rs762551 and read the two-letter genotype, or use a tool that looks it up. 23andMe typically reports this marker on the A/C strand.
Does being a slow caffeine metabolizer matter for health?
Some studies associate slow metabolism plus high coffee intake with modestly higher cardiovascular risk, but evidence is mixed and many factors are involved. This is educational, not medical advice — talk to a clinician about your own situation.
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