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Calcium carbonate

Brand names: Tums, Rolaids, Caltrate, Os-Cal

Calcium carbonate is a chewable antacid for heartburn and a calcium supplement for bone health.

Brand namesTums, Rolaids, Caltrate, Os-Cal
Type of medicineAntacid and calcium supplement
Prescription?Over the counter
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

As an antacid, it works within minutes but doesn't last long.

What it's used for

  • Heartburn and acid indigestion
  • Calcium supplement

How to take it

  • Chew antacid tablets well when symptoms occur.
  • As a supplement, take it with food for better absorption, splitting large amounts through the day.
  • Follow the label's daily limit.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Constipation
  • Gas or burping
Call your provider todayNausea, vomiting, confusion, or extreme thirst (too much calcium)
Call your provider todayHeartburn needing antacids most days for more than 2 weeks

Warnings

  • Too much can cause kidney stones or high calcium, especially with kidney disease.

Other medicines, foods, and alcohol

  • It blocks absorption of levothyroxine, iron, some antibiotics (doxycycline, ciprofloxacin), and alendronate; separate by several hours.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Commonly used for heartburn in pregnancy. Ask about daily limits.

Missed doses, overdose, and storage

If you miss a dose

This medicine is often taken only when needed. If you take it on a schedule, take a missed dose when you remember, unless it's almost time for the next one. Don't double up.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.