Appropriate Dosing of Calcium Carbonate (Tums) for Hypocalcemia
For treating hypocalcemia in adults, calcium carbonate (Tums) should be administered at a dose of 1-2 grams of elemental calcium per day, divided into multiple doses (3-4 times daily) to maximize absorption and minimize gastrointestinal side effects. 1
Calcium Carbonate Considerations
Calcium carbonate contains 40% elemental calcium, making it one of the most cost-effective calcium supplements available. This means:
- A 1250 mg calcium carbonate tablet provides approximately 500 mg of elemental calcium
- For a daily target of 1-2 grams of elemental calcium, 2-4 tablets of 1250 mg calcium carbonate would be needed
Administration Guidelines:
- Take with meals to improve absorption 1
- Divide into 3-4 doses throughout the day to maximize absorption and minimize gastrointestinal side effects
- Monitor serum calcium levels regularly to adjust dosing
Dosing Algorithm Based on Severity
Mild Hypocalcemia (Ionized calcium 1.0-1.12 mmol/L):
- Start with 1 gram of elemental calcium (2500 mg calcium carbonate) daily
- Divide into 3-4 doses taken with meals
- Monitor serum calcium in 24-48 hours 2
Moderate to Severe Hypocalcemia (Ionized calcium <1.0 mmol/L):
- Consider IV calcium gluconate initially (2-4 g) for rapid correction 3
- Transition to oral calcium carbonate at 2 grams of elemental calcium (5000 mg calcium carbonate) daily
- Divide into 4-6 doses taken with meals
- Monitor serum calcium daily until stable 2, 3
Important Monitoring Parameters
- Serum calcium (ionized calcium preferred when available)
- Renal function (creatinine)
- Parathyroid hormone (PTH)
- Magnesium levels (hypomagnesemia can impair PTH function)
- Vitamin D levels 1
Potential Complications and Management
Constipation
Calcium carbonate commonly causes constipation due to its binding with intestinal contents, slowing transit time, and reducing intestinal water content 1:
- Ensure adequate hydration
- Consider polyethylene glycol (MiraLAX) as a first-line treatment
- Docusate sodium may be used as a stool softener
- Increase dietary fiber intake
Absorption Issues
- Achlorhydria (lack of stomach acid) may reduce calcium carbonate absorption 4
- For patients with achlorhydria or those taking proton pump inhibitors, consider calcium citrate as an alternative (contains 21% elemental calcium) 1
Risk of Hypercalcemia
- Do not exceed 2000 mg/day of total elemental calcium intake (dietary + supplements) 1
- Monitor for symptoms of hypercalcemia (nausea, vomiting, constipation, polyuria)
- Patients with chronic kidney disease require careful monitoring to avoid soft tissue calcification 1
Additional Considerations
- Ensure adequate vitamin D supplementation (400-1000 IU daily) to optimize calcium absorption 1
- Consider calcium citrate instead of calcium carbonate in patients with gastrointestinal symptoms or achlorhydria 1, 4
- For patients with persistent hypocalcemia despite oral supplementation, evaluate for vitamin D deficiency, hypomagnesemia, or underlying parathyroid disorders 5
Remember that calcium carbonate should be taken with meals to improve absorption, and the total daily dose should be divided into multiple administrations to maximize effectiveness while minimizing side effects.