What is the recommended dose, administration, and safety considerations for using Tums (calcium carbonate) as an over‑the‑counter antacid?

Tums (Calcium Carbonate) Dosing and Safety

For over-the-counter antacid use, do not exceed 5 chewable tablets (typically 2,000–2,500 mg calcium carbonate) in 24 hours or use maximum dosage for more than 2 weeks without physician supervision. 1

Standard Dosing for Antacid Use

• Maximum daily limit: The FDA label explicitly states not to take more than 5 chewable tablets in a 24-hour period 1
• Duration limit: Do not use maximum dosage for more than 2 weeks except under physician advice 1
• Timing with meals: Calcium carbonate requires gastric acid for optimal absorption and should be taken with food 2, 3
• Divided dosing: For calcium supplementation purposes (not just antacid use), doses should not exceed 500–600 mg elemental calcium at one time to optimize absorption and minimize gastrointestinal side effects 2, 3

Elemental Calcium Content by Formulation

Calcium carbonate contains 40% elemental calcium—the highest concentration among calcium supplements 2, 4:

• TUMS EX (extra strength): 750 mg tablet = 300 mg elemental calcium 2
• TUMS Ultra: 1,000 mg tablet = 400 mg elemental calcium 2
• TUMS 500: 1,250 mg tablet = 500 mg elemental calcium 2

Administration Guidelines

• With meals required: Calcium carbonate dissolution depends on gastric acidity, making administration with meals essential for absorption 4, 3
• Chewable formulation: Chewing the tablets enhances dissolution and may improve esophageal motility in heartburn sufferers 5
• Onset and duration: Calcium carbonate has rapid onset (neutralizes acid within 30 minutes) but short duration of action (only 60 minutes) 6

Safety Considerations and Contraindications

Common Side Effects

• Constipation: The FDA label explicitly warns that "constipation may occur" with use 1, and clinical guidelines identify calcium carbonate as a common cause of constipation and bloating 4
• GI symptoms: Calcium carbonate is more likely to produce constipation, bloating, and reflux symptoms compared to calcium citrate 4, 3

Drug Interactions

• Prescription medications: Consult a physician or pharmacist before use if taking prescription drugs, as antacids may interact with certain medications 1
• Acid-reducing medications: For patients on proton pump inhibitors or H2-blockers, calcium citrate is preferred over calcium carbonate due to reduced dependence on gastric acid for absorption 2, 3

Serious Adverse Effects

• Hypercalcemic crisis: Excessive calcium carbonate ingestion can cause life-threatening hypercalcemia leading to renal failure and altered mental status 7
• Upper limit: Total daily calcium intake (from all sources) should not exceed 2,500 mg per day 2
• Kidney stone risk: Calcium supplements (versus dietary calcium) may increase risk of nephrolithiasis in susceptible patients 2

When to Switch to Calcium Citrate

For patients who develop constipation, bloating, or worsening reflux while using calcium carbonate, switch to calcium citrate 4, 3:

• Calcium citrate provides 21% elemental calcium and causes fewer GI side effects 4, 3
• Can be taken with or without food, offering greater dosing flexibility 4
• Preferred for patients with GERD or those taking acid-reducing medications 3
• Does not require gastric acid for absorption 2, 3

Common Pitfalls to Avoid

• Exceeding daily limits: Do not take more than 5 tablets per day or use for more than 2 weeks at maximum dose without medical supervision 1
• Single large doses: Avoid taking more than 500–600 mg elemental calcium at once; divide doses throughout the day 2, 3
• Ignoring constipation: If constipation develops, switch to calcium citrate rather than continuing calcium carbonate 4
• Use with acid suppressors: Patients on PPIs or H2-blockers should use calcium citrate instead 2, 3
• Replacing dietary calcium: Supplements should complement, not replace, dietary calcium intake 3