Calcium supplements: Do they interfere with blood pressure drugs?

In large amounts, calcium supplements taken by mouth may affect blood pressure medicines called thiazide diuretics. These medicines also are known as water pills. Taking large amounts of calcium with thiazide diuretics can raise the risk of a serious condition called milk-alkali syndrome. Some examples of thiazide diuretics are hydrochlorothiazide (Microzide) and indapamide.

In general, don't take or eat large amounts of calcium daily if you're taking a thiazide diuretic. Calcium sources include supplements and foods that contain calcium.

If you take calcium supplements while taking a thiazide diuretic, talk with your healthcare professional about the right dose of calcium. Also ask to have your blood pressure and calcium levels checked regularly.

Calcium supplements taken by mouth don't appear to affect other commonly prescribed blood pressure medicines such as:

• Angiotensin 2 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 (Kapspargo Sprinkle, Lopressor, Toprol-XL) and others.
• Calcium channel blockers, including nifedipine (Procardia), diltiazem (Cardizem, Cartia XT, others), verapamil (Verelan) and others. Calcium supplements taken by mouth don't interfere with these medicines. But calcium given through a vein (IV) can lessen the effects of calcium channel blockers.
• Renin inhibitors, including aliskiren (Tekturna).

Talk with your healthcare professional if you're concerned about any risks of taking high blood pressure medicines and calcium supplements. Depending on your specific medicines and health needs, your healthcare professional or pharmacist should review the type of calcium you take, the dose and the timing of your dose.