Calcium carbonate is a widely used calcium supplement that helps maintain bone health. It is available as a generic medication and marketed under brand names such as Caltrate and Tums. In Hong Kong, calcium carbonate tablets are sold over-the-counter and are regulated by the Department of Health under the Pharmacy and Poisons Ordinance.
Calcium carbonate supplies elemental calcium, a mineral essential for building and maintaining the skeleton. After ingestion, calcium carbonate is absorbed mainly in the small intestine when the stomach environment is acidic. The released calcium joins the bone matrix, supporting bone mineralization and helping to preserve bone density. Calcium also plays a role in nerve transmission, muscle contraction, and blood clotting.
Calcium carbonate is approved in Hong Kong for the following indications:
These uses are based on the established role of calcium in bone remodeling and on clinical guidelines from international bodies such as the World Health Organization and the International Osteoporosis Foundation.
Who should consider calcium carbonate?
Absolute contraindications
Relative contraindications
This article provides educational information about calcium carbonate and is not a substitute for professional medical advice. Treatment decisions, including use for unapproved indications, must be made under the guidance of a qualified healthcare provider. The content is intended for informational purposes and does not constitute medical recommendations. Always consult a physician before starting, stopping, or changing any medication regimen.
Yes. Vitamin D enhances calcium absorption, and many clinicians recommend combining calcium carbonate with vitamin D to support bone health. However, dosage should be discussed with a healthcare professional to avoid excessive calcium intake.
Calcium carbonate contains a higher proportion of elemental calcium (≈ 40 %) but requires an acidic gastric environment for optimal absorption. Calcium citrate provides about 21 % elemental calcium and is better absorbed in individuals with reduced stomach acidity.
Low-sodium diets are generally compatible with calcium carbonate. In fact, reducing sodium intake can help minimize calcium loss through the kidneys, potentially enhancing the supplement’s effectiveness.
Keep the blister pack tightly sealed and store it in a cool, dry place away from direct sunlight and moisture. Using a moisture-absorbing packet inside the container can provide additional protection.
High calcium levels can affect certain laboratory measurements, such as serum calcium and creatinine. It is advisable to inform the laboratory about calcium supplement use before testing.
Constipation is a common mild side effect. Increasing fluid intake, consuming dietary fiber, and taking the tablets with meals can help alleviate this issue.
Athletes may lose calcium through sweat, but excess supplementation without monitoring can lead to hypercalcaemia. A balanced diet plus individualized supplementation, determined by a sports nutritionist, is recommended.
Typically, calcium carbonate does not need to be stopped before most surgical procedures. However, if you are scheduled for a surgery that requires anticoagulation or specific electrolyte management, discuss timing with your surgeon.
High calcium intake has not been directly linked to worsening hypertension. Nonetheless, people with high blood pressure should monitor overall sodium and potassium intake, as these electrolytes more directly influence blood pressure control.
Do not attempt to self-treat. Contact a healthcare professional or local poison control centre for guidance. Symptoms of overdose may include nausea, vomiting, and abdominal pain.
