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Active ingredient Calcium interacts in the following cases:

Severe renal failure (creatinine clearance of less than 30 ml/minute)

In patients with severe renal failure having a creatinine clearance of less than 30 ml/minute, dosage adjustments may be necessary dependent on serum calcium levels.

Iron, zinc, strontium

Calcium salts may decrease the absorption of iron, zinc and strontium ranelate. Consequently, iron, zinc or strontium ranelate preparations should be taken two hours before or after calcium carbonate.

Cardiac glycosides

Hypercalcaemia may increase the toxicity of cardiac glycosides during treatment with calcium. Patients should be monitored with regard to electrocardiogram (ECG) and serum calcium levels.

Thiazide diuretics

Thiazide diuretics reduce the urinary excretion of calcium. Due to increased risk of hypercalcaemia, serum calcium should be regularly monitored during concomitant use of thiazide diuretics.


Calcium carbonate may interfere with the absorption of concomitantly administered tetracycline preparations. For this reason, tetracycline preparations should be administered at least two hours before, or four to six hours after, oral intake of calcium.

Quinolone antibiotics

The absorption of quinolone antibiotics may be impaired if administered concomitantly with calcium. Quinolone antibiotics should be taken two hours before or after intake of calcium.


If a bisphosphonate is used concomitantly, this preparation should be administered at least three hours before the intake of calcium since gastrointestinal absorption may be reduced.


The efficacy of levothyroxine can be reduced by the concurrent use of calcium, due to decreased levothyroxine absorption. Administration of calcium and levothyroxine should be separated by at least four hours.


Calcium can be used during pregnancy. Daily intake should not exceed 2500 mg of calcium as permanent hypercalcaemia has been related to adverse effects on the developing foetus.

Nursing Mothers

Calcium carbonate can be used during breast-feeding. Calcium passes into breast milk but at therapeutic doses no effects on the breastfed new-born are anticipated.

Effects on Ability to Drive and Use Machines

Calcium carbonate has no known influence on ability to drive and use machines.