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

Answers from Sheldon G. Sheps, M.D.

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

  • Thiazide diuretics. Taking 1,500 milligrams (mg) or more of calcium with thiazide diuretics — such as chlorothiazide (Diuril), hydrochlorothiazide (Microzide, Oretic) and indapamide — can result in milk-alkali syndrome, a serious condition.

    In general, avoid taking more than 1,500 mg of calcium (supplements and food sources combined) a day if you're taking a thiazide diuretic (also referred to as water pills).

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

  • Calcium channel blockers. When given through an intravenous (IV) line, calcium may decrease the effects of calcium channel blockers, such as nifedipine (Adalat CC, Afeditab CR, Procardia), verapamil (Calan, Covera-HS, Tarka), diltiazem (Cardizem, Cartia XT, Dilacor XR, others) and others. In fact, IV calcium is used to help reverse calcium channel blocker overdose.

    There's no evidence that oral calcium supplements interfere with calcium channel blockers. 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:

  • Beta blockers bisoprolol (Zebeta), propranolol (Inderal, Innopran XL) and others
  • Angiotensin-converting enzyme (ACE) inhibitors, such as captopril (Capoten), lisinopril (Prinivil, Zestril) and others
  • Angiotensin II receptor blockers, such as losartan (Cozaar), valsartan (Diovan), and others
  • Renin inhibitors, such as aliskiren (Tekturna)

Talk to your doctor if you take high blood pressure medications and calcium supplements and are concerned about interactions.

Aug. 15, 2015 See more Expert Answers