Open Community Question @PrairieWalker_KS • 45-59F • Omeprazole 20 mg daily • Week 208

▲ 42 Helpful • 2 Peer Replies

How long can I take omeprazole 20 mg daily before low magnesium and B12 become a concern, and which labs should I ask for?

Public question: "I've taken omeprazole 20 mg daily for 4 years for GERD. Should I be tested for anything?" Evidence Desk answer: The omeprazole label warns about hypomagnesemia, usually after a year of use but sometimes within 3 months. It also warns about vitamin B12 deficiency with long-term use, generally over 3 years. Reasonable labs to ask about are serum magnesium (typical reference range about 1.7-2.2 mg/dL, varying by lab) and serum B12. B12 under 200 pg/mL is deficient, and 200-300 pg/mL is borderline, where methylmalonic acid (above 0.4 umol/L suggests deficiency) helps clarify. Symptoms such as muscle cramps, palpitations, numbness, or fatigue deserve prompt testing. Do not stop a PPI abruptly on your own, especially with a history of ulcer or bleeding. Ask your prescriber whether you still need the dose.

⚕ Pinned FDA / NIH / PubMed Clinical Context • Karim El-Sayed — Literature & Label Auditor

FDA DailyMed omeprazole labeling lists hypomagnesemia (usually after 1 year, occasionally 3 months) and B12 deficiency with use over 3 years, and advises checking magnesium before and periodically during long-term treatment. NIH ODS sets the adult B12 RDA at 2.4 mcg/day and the supplemental magnesium upper limit at 350 mg/day.

Connected Clinical Guides: Condition: Gastroesophageal Reflux Disease Condition: Irritable Bowel Syndrome Rx: Omeprazole Rx: Pantoprazole Supplement: Magnesium Glycinate Supplement: Vitamin B12

Find Gastroenterologists (CPT 45378 / 43239) →

Verified Peer Replies (2)

@MaintenanceMode_WA • Verified Cohort Member • Week 28

Practical addition: if magnesium is low, a prescriber may add oral magnesium or reduce the PPI dose. Magnesium glycinate is often better tolerated than oxide, though kidney function matters. Keep supplemental magnesium at or under 350 mg elemental per day unless your clinician directs otherwise, and recheck levels in about 8-12 weeks.

@SpineRecovery_PA • Age 60+ • Week 20

My B12 was 228 pg/mL after years on pantoprazole. My doctor added MMA, which came back mildly high, so I started 1000 mcg oral B12 daily. Crystalline B12 in supplements doesn't need stomach acid to be absorbed, which was reassuring. Recheck was at 12 weeks.