Oyster Calcium Side Effects

Generic Name: calcium carbonate

Note: This page contains side effects data for the generic drug calcium carbonate. It is possible that some of the dosage forms included below may not apply to the brand name Oyster Calcium.

It is possible that some side effects of Oyster Calcium may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

For the Consumer

Applies to calcium carbonate: chewable tablets

Other dosage forms:

No COMMON side effects have been reported with this medicine. Seek medical attention right away if any of these SEVERE side effects occur while taking calcium carbonate (the active ingredient contained in Oyster Calcium)

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue).

For Healthcare Professionals

Applies to calcium carbonate: compounding powder, oral capsule, oral gum, oral powder, oral suspension, oral tablet, oral tablet chewable


Rebound hyperacidity has been associated with calcium salt antacids. This side effect does not appear to be due to the acid buffering capacity of calcium carbonate (the active ingredient contained in Oyster Calcium) but is a consequence of a specific action of calcium on the parietal cell.

Rare cases of calcium carbonate gallstones have been reported in the pediatric literature.

Gastrointestinal side effects have included rebound hyperacidity, constipation (6% to 37%) and gallstones (rarely).


Prolonged ingestion of large amounts of calcium carbonate (the active ingredient contained in Oyster Calcium) and other sources of exogenous calcium can rarely result in the "milk alkali syndrome" and calcinosis. The milk alkali syndrome is characterized by the triad of hypercalcemia, metabolic alkalosis, and renal insufficiency.

Metabolic side effects have rarely included hypercalcemia and hypophosphatemia. Hypercalcemia may be more likely and more severe in patients with renal dysfunction. In patients on chronic dialysis, hypercalcemia may also result from excessive calcium in the dialysate, vitamin D intoxication, or severe secondary hyperparathyroidism. Other metabolic side effects have rarely included "mild alkali syndrome", calcinosis, and irreversible renal damage.


Renal side effects have included renal failure, formation of renal calcium and a single case report of a calcium carbonate (the active ingredient contained in Oyster Calcium) and calcium phosphate-filled renal cyst.

The renal failure that accompanies hypercalcemia and alkalosis in the milk alkali syndrome is usually transient.

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