Is CYP1A2 useful for fatigue?

CYP1A2 encodes an enzyme primarily responsible for caffeine metabolism. DTC genetic tests often highlight variants (e.g., rs762551) to suggest personalized caffeine timing for energy and fatigue management. However, the evidence for using CYP1A2 to address fatigue is weak. Fatigue is multifactorial—sleep quality, stress, nutrition, and underlying medical conditions dominate. While caffeine metabolism is genetically influenced, no robust clinical trials show that adjusting intake based on CYP1A2 genotype meaningfully reduces fatigue in the general population. Most claims are marketing-driven, not evidence-based. A genetic test cannot replace a medical workup for chronic fatigue (e.g., anemia, thyroid disorders, sleep apnea). In summary, CYP1A2 is not clinically useful for fatigue; its role is limited to mechanistic speculation.