rs12248560
A SNP in the CYP2C19 gene on chromosome 10. Its most notable genotype is C;T: CYP2C19*17 ultra fast metabolizer; drug metabolism effects; also 0.77x decreased breast cancer risk
- Gene
- CYP2C19
- Location
- Chr 1094,761,900 (GRCh38)
- Highest magnitude
- 2.0Worth knowing
- Tested on
- 23andMe, AncestryDNA
- Minor allele frequency
- 15%
Genotypes
As shown in 23andMe and AncestryDNA files.
- C;CGoodnormal
- C;TMost notableNot ratedCYP2C19*17 ultra fast metabolizer; drug metabolism effects; also 0.77x decreased breast cancer risk
- T;TNot ratedCYP2C19*17 ultra fast metabolizer; drug metabolism effects; also 0.77x decreased breast cancer risk
On SNPedia: (C;C), (C;T), (T;T). Magnitude rates how notable a genotype is from 0 to 10, not how risky it is.
Frequency
Share of each genotype in 4 HapMap populations.
- AverageC;C 76% C;T 21% T;T 3%
- European ancestry (Utah)C;C 55% C;T 43% T;T 2%
- Han Chinese (Beijing)C;C 96% C;T 4% T;T 0%
- Japanese (Tokyo)C;C 100% C;T 0% T;T 0%
- Yoruba (Nigeria)C;C 52% C;T 38% T;T 10%
Related
Conditions, medicines and genes
Other CYP2C19 SNPs
- rs4244285A;Apoor metabolizer of several popular medicines; patients prescribed Plavix get less benefit, and have higher risk for adverse cardiovascular eventsVery important
- rs6413438T;TCYP2C19*10 homozygoteImportant
- rs41291556C;CCYP2C19*8 homozygoteImportant
- rs56337013T;TCYP2C19*5 homozygoteImportant
- rs28399504G;Gpoor metabolizerWorth knowing
- rs4986893A;Apoor metabolizer of several commonly prescribed drugsWorth knowing
- rs3758580C;Ccommon/normalTypical
- rs3758581A;ACYP2C19 V331I homozygoteTypical
Genosets
- Gs153CYP2C19 Extensive or Ultra-Fast MetabolizerImportant
- Gs150CYP2C19 normal/rapid metabolizer (most likely)Minor
Genosets combine several genotypes. Twofold checks them in your report.
Notes
From SNPedia
Show notes, about 160 words
rs12248560(T) defines the CYP2C19*17 allele, an ultra fast metabolizer phenotype of the CYP2C19 gene. CYP2C19*17 is likely to lead to less effective drug treatment by, for example, proton pump inhibitors (such as omeprazole) and antidepressants. On the other hand, cancer patients who are CYP2C19*17 carriers are more likely to benefit from tamoxifen treatment, presumably because they break it down more rapidly into the antiestrogenic metabolites endoxifen and 4-hydroxytamoxifen. A study of 1,000+ breast cancer patients showed a 0.77x decreased risk of breast cancer for carriers of a CYP2C19*17 allele (CI: 0.65-0.93, p = 0.005). Analysis of a subgroup of such carriers who were using hormone therapy for ten years or longer showed an even stronger effect (odds ratio 0.57, CI: 0.39-0.83, p = 0.003). The theory is that ultra fast metabolism of estrogen leads to lower estrogen levels and lower breast cancer risk. Clopidogrel Efficacy
Source and license
Adapted from rs12248560 on SNPedia, using a snapshot taken October 16, 2026. SNPedia content is shared under CC BY-NC-SA 3.0 US, and this page is shared under the same license.
SNPedia is a community-edited wiki. Its entries can be incomplete, out of date or wrong, and nothing here is a diagnosis or medical advice. Magnitude is a community rating of how interesting a genotype is, not a risk score.