by EBSCO CAM Review Board

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
Vitamin B12

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.


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.

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.


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.

Vitamin D

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.


REF1 Salom IL, Silvis SE, Doscherholmen A. Effect of cimetidine on the absorption of vitamin B 12 . Scand J Gastroenterol 17: 129–131, 1982.

REF2 Streeter AM, Goulston KJ, Bathur FA, et al. Cimetidine and malabsorption of cobalamin. Dig Dis Sci 27: 13–16, 1982.

REF3 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.

REF4 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.

REF5 D'Arcy PF and McElnay JC. Drug interactions in the gut involving metal ions. Rev DrugMetabol Drug Interact 5(2–3):83–112, 1985.

REF6 Hathcock JN. Metabolic mechanisms of drug-nutrient interactions. Fed Proc 44(1): 124, 1985.

REF7 Sturniolo GC, et al. Inhibition of gastric acid secretion reduces zinc absorption in man. JAm Coll Nutr 4: 372–375, 1991.

REF8 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.

REF9 Bachmann KA, Sullivan TJ, Jauregui L, et al. Drug interactions of H 2 -receptor antagonists. Scand J Gastroenterol Suppl 206: 14–19, 1994.

REF10 Bengoa JM, et al. Hepatic vitamin D 25-hydroxylase inhibition by cimetidine and isoniazid. J Lab Clin Med 104: 546–552, 1984.

REF11 Anonymous. Cimetidine inhibits the hepatic hydroxylation of vitamin D. Nutr Rev 43: 184–185, 1985.

REF12 Odes HS. Effect of cimetidine on hepatic vitamin D metabolism in humans. Digestion 46(2): 61–64, 1990.

Revision Information

  • Reviewer: EBSCO CAM Review Board
  • Review Date: 12/2015
  • Update Date: 04/02/2020