H2 Blockers

Medications in this family sharply decrease stomach acid production. They are widely used for the treatment of ulcers as well as for mild cases of esophageal reflux (heartburn).

Drugs that fall into this family include

  • cimetidine (Tagamet, Tagamet HB)
  • famotidine (Pepcid, Pepcid AC, Pepcid RPD)
  • nizatidine (Axid, Axid AR)
  • and others
Probable Need for Supplementation

H 2 -receptor blockers appear to impair the absorption of vitamin B 12 from food.1,2,3 This is thought to occur because the vitamin B 12 in food is attached to proteins. Stomach acid separates them and allows the B 12 to be absorbed.

The solution? If you regularly use H 2 blockers, take B 12 supplements. They can be absorbed easily because they are not attached to proteins.

Supplementation Possibly Helpful

There is some evidence that H 2 blockers may slightly reduce the absorption of folate.4 Folate is an important nutrient and one that is commonly deficient in the diet; so if you are taking H 2 blockers, you should probably take folate supplements, too.

Supplementation Possibly Helpful

By reducing stomach acid levels, H 2 blockers might interfere with the absorption of iron, zinc, and perhaps other minerals.5–8 Taking mineral supplements that provide the U.S. Dietary Reference Intake (formerly known as the Recommended Dietary Allowance) of these substances should help.

Take at a Different Time of Day

Magnesium supplements may interfere with the absorption of H 2 blockers.9 However, the interference may be too minor to cause a real problem. If you think your magnesium supplements are interfering with your medication, you can get around the problem by taking these minerals at least 2 hours before or after you take an H 2 -blocking medication.

Possible Inhibition by Cimetidine

Cimetidine may interfere with vitamin D metabolism.10,11,12 Other H 2 blockers may not interact. Whether taking more vitamin D is useful remains unknown.


1. Salom IL, Silvis SE, Doscherholmen A. Effect of cimetidine on the absorption of vitamin B 12. Scand J Gastroenterol 17: 129–131, 1982.

2. Streeter AM, Goulston KJ, Bathur FA, et al. Cimetidine and malabsorption of cobalamin. Dig Dis Sci 27: 13–16, 1982.

3. Blache J, Zittoun J, Marquet J, et al. Effect of ranitidine on secretion of gastric intrinsic factor and absorption of vitamin B 12. Gastroenterol Clin Biol 7: 381–384, 1983.

4. Russell RM, Golner BB, Krasinski SD, et al. Effect of antacid and H 2 receptor antagonists on the intestinal absorption of folic acid. J Lab Clin Med 112: 458–463, 1988.

5. D'Arcy PF and McElnay JC. Drug interactions in the gut involving metal ions. Rev DrugMetabol Drug Interact 5(2–3):83–112, 1985.

6. Hathcock JN. Metabolic mechanisms of drug-nutrient interactions. Fed Proc 44(1): 124, 1985.

7. Sturniolo GC, et al. Inhibition of gastric acid secretion reduces zinc absorption in man. JAm Coll Nutr 4: 372–375, 1991.

8. Aymard JP, Aymard B, Netter P, et al. Haematological adverse effects of histamine H 2 -receptor antagonists. Med Toxicol Adverse Drug Exp 3: 430–448, 1988.

9. Bachmann KA, Sullivan TJ, Jauregui L, et al. Drug interactions of H 2 -receptor antagonists. Scand J Gastroenterol Suppl 206: 14–19, 1994.

10. Bengoa JM, et al. Hepatic vitamin D 25-hydroxylase inhibition by cimetidine and isoniazid. J Lab Clin Med 104: 546–552, 1984.

11. Anonymous. Cimetidine inhibits the hepatic hydroxylation of vitamin D. Nutr Rev 43: 184–185, 1985.

12. Odes HS. Effect of cimetidine on hepatic vitamin D metabolism in humans. Digestion 46(2): 61–64, 1990.

Last reviewed December 2015 by EBSCO CAM Review Board

EBSCO Information Services is fully accredited by URAC. URAC is an independent, nonprofit health care accrediting organization dedicated to promoting health care quality through accreditation, certification and commendation.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

To send comments or feedback to our Editorial Team regarding the content please email us at healthlibrarysupport@ebsco.com. Our Health Library Support team will respond to your email request within 2 business days.