Is it true that calcium supplements may interact with blood pressure medications?

Answer From Carrie Krieger, Pharm.D.

Yes. In large amounts, calcium supplements may interact with some blood pressure medications. Interactions may occur with:

  • Thiazide diuretics. These medications are also referred to as water pills. Taking large amounts of calcium with thiazide diuretics — such as chlorothiazide (Diuril), hydrochlorothiazide (Microzide) and indapamide — can increase the risk of milk-alkali syndrome, a serious condition.

    In general, avoid taking large amounts of calcium daily if you're taking a thiazide diuretic. This includes calcium supplements and calcium food sources.

    If you take calcium supplements while taking a thiazide diuretic, talk to your health care provider about the appropriate dose. Also ask to have your blood pressure and calcium levels checked.

  • Calcium channel blockers. Supplemental calcium may decrease the effects of calcium channel blockers, such as nifedipine (Procardia), verapamil (Calan SR, Verelan), diltiazem (Cardizem, Cartia XT, others) and others. In fact, calcium is delivered through an IV line to help reverse a calcium channel blocker overdose.

    To be safe, check your blood pressure regularly if taking calcium channel blockers and calcium supplements at the same time.

Calcium supplements don't appear to interact with other commonly prescribed blood pressure medications, such as:

  • Angiotensin II receptor blockers, including losartan (Cozaar), valsartan (Diovan) and others
  • Angiotensin-converting enzyme (ACE) inhibitors, including captopril, lisinopril (Zestril) and others
  • Beta blockers, including carvedilol (Coreg) and metoprolol (Lopressor, Toprol-XL, Kapspargo Sprinkle) and others
  • Renin inhibitors, including aliskiren (Tekturna)

Talk to your care provider if you take high blood pressure medications and calcium supplements and are concerned about interactions. Depending on your specific medications, you may need to take a calcium supplement with or between meals.


Carrie Krieger, Pharm.D.

Aug. 27, 2022