rs1801131 MTHFR
MTHFR A1298C homozygous. Reduced enzyme activity; combined with C677T increases homocysteine risk.
What is rs1801131?
rs1801131 is a single-nucleotide polymorphism (SNP) in the MTHFR gene (Methylenetetrahydrofolate reductase). Each person carries two copies, one from each parent, so a result is reported as a pair of letters such as GG. The table below describes what studies associate with each genotype; the association is statistical, across populations, and is not a diagnosis.
What does each rs1801131 genotype mean?
| Genotype | Association | What the evidence says | Confidence |
|---|---|---|---|
| GG | increased | MTHFR A1298C homozygous. Reduced enzyme activity; combined with C677T increases homocysteine risk. | 82% |
| TG / GT | typical | MTHFR A1298C heterozygous. Mildly reduced activity. | 78% |
| TT | typical | Normal MTHFR at A1298C position. | 82% |
How common is the G allele of rs1801131?
Minor-allele frequency by population (gnomAD / 1000 Genomes):
| European | 30.0% |
|---|---|
| East Asian | 22.0% |
| African | 12.0% |
| South Asian | 25.0% |
| Admixed American | 28.0% |
| Global | 24.0% |
Which drugs have annotations for rs1801131?
PharmGKB clinical annotations (level 1A is the strongest evidence, 4 the weakest):
| Drug | Annotation type | Evidence level |
|---|---|---|
| nitrous oxide | Toxicity, Efficacy, Dosage | 3 |
| clozapine | Toxicity, Efficacy, Dosage | 3 |
| olanzapine | Toxicity, Efficacy, Dosage | 3 |
| methotrexate | Toxicity | 3 |
Is rs1801131 on 23andMe and AncestryDNA chips?
Yes — it is genotyped directly on 23andMe V3, 23andMe V4, 23andMe V5, AncestryDNA V1, AncestryDNA V2. Orviva reads it from a raw-data export without imputation.
Sources
Upload your 23andMe, AncestryDNA or WeGene raw file → · Ask G2: “What is my genotype at rs1801131 and what does it mean for me?”
Genetic associations describe risk across populations, not a diagnosis for any one person. Most variants shift risk modestly and act alongside lifestyle, environment and other genes. Consumer DNA chips do not read every position and can be wrong at any single one. For general education only; talk to a clinician or genetic counsellor before acting on anything here, and never change a prescribed medicine without your prescriber.