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Supplements and Acid Reducers (PPIs): B12 and Magnesium

This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Long-term use of proton pump inhibitors (PPIs) like omeprazole can lower vitamin B12 and magnesium levels, because...

Long-term use of proton pump inhibitors (PPIs) like omeprazole can lower vitamin B12 and magnesium levels, because stomach acid helps absorb them. Reduced acid can also affect other supplements. If you take a PPI long-term, ask your provider whether your B12 and magnesium should be checked.

Key Takeaways

  • Stomach acid helps absorb several nutrients, so acid-suppressing PPIs can lower some over time.
  • Long-term PPI use can reduce vitamin B12 absorption from food.
  • NIH notes prolonged PPI use (typically over a year) can cause low magnesium (hypomagnesemia).
  • Don't stop a prescribed acid reducer on your own; focus on monitoring and replacement when needed.
  • If you take a PPI long-term, ask whether your B12 and magnesium should be checked.

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How acid reducers change absorption

Stomach acid helps release and absorb several nutrients, so medicines that suppress acid — especially proton pump inhibitors (PPIs) like omeprazole, esomeprazole, and lansoprazole — can reduce the absorption of some nutrients over time [1][2].

Vitamin B12

Stomach acid frees B12 from food so it can be absorbed. NIH notes that PPIs and other acid-suppressing drugs can reduce B12 absorption from food, and long-term use is associated with lower B12 status [1]. (Interestingly, B12 in supplements is less dependent on stomach acid, so a supplement can help when needed.) See vitamin B12 deficiency risk.

Magnesium

NIH reports that prescription PPIs 'can cause hypomagnesemia when taken for prolonged periods (typically more than a year)' [2]. The FDA has also issued a safety communication on low magnesium with long-term PPI use. Severe cases can affect the heart and muscles, so this isn't trivial.

The bigger picture

  • Metformin is another medicine linked to lower B12 over time — see [nutrient depletion from medications](/learn/nutrient-depletion-from-medications).
  • Don't stop a prescribed acid reducer on your own; many people need them. The point is monitoring and replacement when appropriate, not abrupt discontinuation.

Practical guidance

  • If you take a PPI long-term, ask your provider whether B12 and magnesium should be checked periodically.
  • Replace under guidance if levels are low, rather than self-prescribing high doses.
  • Tell your provider about supplements and acid reducers together, since the interaction is about long-term status, not a single dose.

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Frequently Asked Questions

Do acid reducers cause vitamin B12 deficiency?

Long-term use of proton pump inhibitors can reduce B12 absorption from food, because stomach acid is needed to release B12. Over years this is associated with lower B12 status. B12 in supplements is less acid-dependent, so checking levels and supplementing when needed can help.

Can PPIs lower my magnesium?

Yes. NIH notes that prolonged use of prescription PPIs, typically more than a year, can cause low magnesium, and the FDA has issued a safety communication on this. Severe cases can affect the heart and muscles, so long-term PPI users may need their magnesium monitored.

Should I stop my acid reducer to protect my nutrients?

Not on your own. Many people need acid reducers for valid medical reasons, and stopping abruptly can cause problems. The better approach is to ask your provider about periodic monitoring of B12 and magnesium and replacing them under guidance if levels are low.

Does metformin also affect nutrients?

Yes. Metformin is associated with lower vitamin B12 over time, similar in spirit to the PPI effect. This is one reason providers sometimes check B12 in people on long-term metformin, and it's covered further on the nutrient-depletion-from-medications page.

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Supplement Guide

Vitamin B12

Vitamin B12 is essential for energy production, nerve health, and red blood cell formation. Deficiency affects up to 20% of older adults and can cause fatigue, brain fog, and neuropathy. Methylcobalamin is the preferred supplemental form at 500-2,000 mcg daily, and it also helps lower homocysteine levels for cardiovascular protection.

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References

  1. National Institutes of Health, Office of Dietary Supplements (2025). Vitamin B12: Health Professional Fact Sheet. NIH Office of Dietary Supplements.
  2. National Institutes of Health, Office of Dietary Supplements (2026). Magnesium: Health Professional Fact Sheet. NIH Office of Dietary Supplements.