Myths vs facts: CYP2C19 and fatigue

CYP2C19 is a liver enzyme that metabolizes drugs like clopidogrel, proton pump inhibitors, and some antidepressants. Genetic variants (e.g., *2, *17) determine metabolizer status: poor, intermediate, normal, or ultrarapid. **Myth:** CYP2C19 variants directly cause fatigue. **Fact:** No strong evidence links CYP2C19 alone to fatigue. However, drug side effects due to inappropriate dosing can cause tiredness. For example, an ultrarapid metabolizer may clear certain antidepressants too quickly, leading to loss of efficacy and indirectly to exhaustion. The association is indirect and context-dependent. Consumer DNA tests often overstate clinical relevance. Persistent fatigue should be evaluated by a physician before overinterpreting genetic results. Evidence: human-moderate for drug metabolism, but weak for fatigue as a direct symptom.