Genetic variant

rs1801133 a variant in the MTHFR gene

rs1801133 is a single-letter difference in the MTHFR gene, on chromosome 1. ClinVar, the public archive of variant interpretations, lists it as drug response: linked to how the body handles certain medicines. It has been reported in connection with MTHFR thermolabile polymorphism and Gastrointestinal stromal tumor, among others. Carrying it does not, on its own, mean you have or will develop any condition.

ClinVar: Drug response
Drug Response
Chromosome 1

What is this?

Your DNA is a long sequence of four letters. At a few million positions, people commonly differ by a single letter; each of those positions is called a SNP (“snip”), and rs1801133 is the catalogue number of one of them, in the MTHFR gene. Which letters you carry there — one copy from each parent — is your genotype.

MTHFR (methylenetetrahydrofolate reductase): The protein encoded by this gene catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a co-substrate for homocysteine remethylation to methionine. Genetic variation in this gene influences susceptibility to occlusive vascular disease, neural tube defects, colon cancer and acute leukemia, and mutations in this gene are associated with methylenetetrahydrofolate reductase deficiency.[p…
Gene description from NCBI Gene

rs1801133 is a SNP that is relatively common and has been studied for (relatively) a long time. Also...
From SNPedia

Why might it matter?

ClinVar records this variant as drug response, meaning linked to how the body handles certain medicines. A classification describes the variant, not you: what it means for one person depends on their genotype, their family history and often on other genes and circumstances.

Conditions it has been reported with

MTHFR thermolabile polymorphism
Gastrointestinal stromal tumor
Neural tube defects, folate-sensitive
Homocystinuria due to methylene tetrahydrofolate reductase deficiency
methotrexate response - Toxicity
Thrombophilia due to thrombin defect

Listed in ClinVar submissions for this variant. Being listed is a report of an association, not a statement that the variant causes the condition in any given person.

Supplements

Methylfolate (5-MTHF) may support strong

MTHFR C677T — methylfolate bypasses reduced enzyme activity

Vitamin B12 (methylcobalamin) may support moderate

MTHFR C677T — supports methylation cycle

Riboflavin (B2) may support moderate

MTHFR C677T — riboflavin stabilises the MTHFR enzyme

Do I have this variant?

If you have taken a consumer DNA test (23andMe, AncestryDNA and similar), you can download its raw data file and check. Create a free account, upload the file, and this page will show the letters you carry at rs1801133, if your test read this position.

Connect this with your blood results

A gene is a fixed instruction; a blood test shows what your body is doing now. CheckMyBloods reads the two side by side, so a variant can be set against the markers it could plausibly affect.

Blood markers related to MTHFR

MTHFR variants can reduce folate processing efficiency. Monitor folate and B12.

Blood markers do not diagnose a genetic condition, and a variant does not explain a blood result on its own. Together, with symptoms and family history, they give a clinician context.

Upload blood results

What should I do next?

Find out whether you carry it. Reading about a variant says nothing about you until you know your genotype.
Put it in context. Add your blood results, so the variant can be read against what your body is doing.
Ask questions. Dr. Hemsworth, our AI assistant, can explain this variant and your results in plain English.
Take anything that worries you to a professional. A GP or genetic counsellor can order a confirmatory test and interpret it with your history.

This page is general information drawn from public research databases. It cannot diagnose anything, and it is not a substitute for advice from a doctor or genetic counsellor who knows your history.

Technical details

dbSNP ID: rs1801133
Gene: MTHFR
Position (GRCh38): chr1:11796320
Variant type: snv
Consequence: missense variant
ClinVar classification: drug response