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 doctor 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.