MTHFR converts dietary folate into the active form the methylation cycle requires. The C677T (rs1801133) and A1298C (rs1801131) variants reduce enzyme activity by 30–65%, limiting DNA repair, homocysteine clearance, and epigenetic age regulation. The Precision Peptide Genetic Test analyzes MTHFR as part of 17 Longevity & Aging insights spanning 14 pathways, 49 peptides, and 150+ genetic insights.