If you are currently being treated with any of the following medications, you should not use calcium supplements without first talking to your doctor.

Alendronate -- Calcium may interfere with the absorption of alendronate, a medication used to treat osteoporosis. Calcium-containing products should be taken at least 2 hours before or after alendronate.

Antacids that contain aluminum -- When calcium citrate is taken with aluminum-containing antacids, the amount of aluminum absorbed into the blood may be increased significantly. This is a particular problem for people with kidney disease, for whom the aluminum levels may become toxic.

Blood pressure medications -- Taking calcium with a beta-blocker (such as atenolol) may interfere with blood levels of both the calcium and the beta-blocker. Study results are conflicting, however. Similarly, it has been reported that calcium interferes with calcium channel blockers (such as verapamil), but these study results are also controversial. If you take a beta-blocker or calcium-channel blocker, do not take calcium supplements without your doctor’s supervision.

Cholesterol-lowering medications -- A class of medications known as bile acid sequestrants (including cholestyramine, colestipol, and colesevelam), used to treat high cholesterol, may interfere with normal calcium absorption and increase the loss of calcium in the urine. Supplementation, therefore, with calcium and vitamin D may be recommended by your health care provider.

Corticosteroids -- If you take corticosteroids on a long-term basis, you may need to take calcium supplements.

Digoxin -- High levels of calcium may increase the risk of a toxic reaction to digoxin, a medication used to treat irregular heart rhythms. On the other hand, low levels of calcium cause digoxin to be ineffective. If you take digoxin, your doctor should monitor your calcium levels closely.

Diuretics -- Different types of diuretics interact with calcium in opposite ways.

• Thiazide diuretics (such as hydrochlorothiazide) can raise calcium levels in the blood.
• Loop diuretics (such as furosemide and bumetanide) can decrease calcium levels.
• Amiloride (a potassium-sparing diuretic) may decrease the amount of calcium excreted in the urine (thus increasing calcium levels in the blood), especially in people with kidney stones.

Estrogens -- Estrogens may contribute to an overall increase in calcium blood levels. Taking calcium supplements with estrogens improves bone density significantly.

Gentamicin -- Taking calcium during treatment with the antibiotic gentamicin may increase the potential for toxic effects on the kidneys.

Antibiotics -- Different types of antibiotics interact with calcium.

• Quinolones: Calcium can interfere with the body's ability to absorb quinolone antibiotics (such as ciprofloxacin or Cipro; levofloxacin, norfloxacin or Noroxin; and ofloxacin). Take calcium supplements 2 - 4 hours before or after taking quinolone antibiotics
• Tetracyclines: Calcium can interfere with the body's ability to absorb tetracycline antibiotics (including doxycycline, minocycline, and tetracycline). Take calcium supplements 2 -4 hours before or after taking quinolone antibiotics.

Anti-seizure medications -- Some seizure medications, such as phenytoin (Dilantin), carbamazepine, phenobarbitol, and primidone, may lower levels of calcium in the body. Some doctors recommend vitamin D along with anti-seizure drugs to try to keep calcium levels up. In addition, you should take doses of calcium and anti-seizure medications at least 2 hours apart, because each interferes with the absorption of the other.