Omeprazole is America's #1 most prescribed acid drug — but 65% of long-term users develop B12 deficiency and fracture risk rises 25–44%. This 2026 complete guide covers how the proton pump works, why taking it after meals reduces efficacy, the acid rebound trap when stopping, the clopidogrel CYP2C19 interaction for heart patients, a 6-PPI comparison table, and who genuinely needs it long-term vs who should taper off.