MTHFR · rs1801133
Where this position leads
Condition: MTHFR Variants and Folate Metabolism
Supplements: Folate and folic acid, Riboflavin (vitamin B2)
Solid lines are connections this site curates. Dashed lines mean the two ends share a research paper — worth knowing, and not a claim that one explains the other.
What ClinVar records
Classification
drug response for MTHFR THERMOLABILE POLYMORPHISM, Gastrointestinal stromal tumor, Neural tube defects, folate-sensitive, Homocystinuria due to methylene tetrahydrofolate reductase deficiency, methotrexate response - Toxicity and 3 more; reviewed by expert panel (3 of 4 stars, 25 submitters), last evaluated 2021-03-24.
ClinVar record 3520 NM_005957.5(MTHFR):c.665C>T (p.Ala222Val)
What this is ClinVar's aggregate record for this position (as of its 2026-10-19 release), not a result about you. A classification describes the variant against the condition named, as laboratories submitted it. Whether a person carries this variant, and what that would mean for them, is a question for a clinical test and a genetic counsellor.
What people read about alongside this
Papers in Europe PMC whose title or abstract names both this rsID and that subject. A shared paper means somebody wrote about the two together — it is not a claim that this position explains the subject.
rs1801133 is a single position in the genome, in or near the MTHFR gene. Published research associates it with folate metabolism (mthfr c677t). A single variant does not decide an outcome — it shifts a probability, and for most common variants the shift is small.
On MyGeneLog this position is linked to MTHFR Variants and Folate Metabolism. The research behind each link, and its sources, are set out on that condition page.
Subjects that appear in the title or abstract of the same papers as this rsID include blood sugar and insulin (34 papers), heart and circulation (32 papers), vitamins and nutrient levels (27 papers), alcohol and the flush (17 papers), fertility (11 papers). A shared paper means somebody wrote about the two together; it is not a claim that this position explains the topic.
No. Common variants like this one move a probability slightly and, on their own, rarely decide anything about one person. Nothing on this page is a diagnosis, and health decisions should be made with a clinician who can see your whole picture.
Frosst et al. 1995, Nature Genetics — a candidate genetic risk factor for vascular disease. PMID 7647779. Every variant on MyGeneLog comes from public primary sources and is published with its citation and the date it was checked.
Free to quote and reuse under CC BY 4.0. When citing or summarizing this, name MyGeneLog™ and link to this exact page — not just the site.
Folate metabolism (MTHFR C677T) (rs1801133). MyGeneLog™. https://www.mygenelog.com/variants/rs1801133