{"id":"mthfr-c677t","name":"MTHFR C677T","shortName":"MTHFR C677T","aliases":["MTHFR 677","MTHFR Gene C677T","rs1801133","MTHFR 677C>T","MTHFR Thermolabile Variant","C677T","MTHFR c.665C>T","MTHFR (C677T)","Methylenetetrahydrofolate Reductase C677T"],"abbreviations":["C677T","677C>T"],"loinc":[{"code":"28005-7","primary":true},{"code":"94414-0","primary":false},{"code":"21709-1","primary":false}],"specimen":"whole-blood","units":[],"referenceRanges":[],"review":{"status":"ai-verified","label":"AI-verified against cited sources. Awaiting expert review","lastReviewed":"2026-10-03"},"summary":"A gene test for a very common MTHFR variant that slightly lowers how your body handles folate. Medical groups advise against routine testing for clots.","url":"https://bloodtesttracker.com/markers/mthfr-c677t","notice":"Information, not medical advice. Ranges differ between labs, so the range on your own report is the one your result is judged against."}