Calcium carbonate is a common supplement for people with low calcium levels. It’s also useful as an antacid to manage uncomfortable digestive symptoms.

Calcium carbonate (CaCO3) is a compound used as a dietary calcium supplement and as a common antacid. It is one of the most abundant compounds in the earth’s crust and is found naturally in:

  • egg and oyster shells
  • the outer skeletons of crustaceans
  • dark leafy greens such as kale

Calcium carbonate is available over-the-counter as Alka-Seltzer, Tums, Rolaids, and Pepto-Bismol, to name a few medications. Although calcium carbonate products and supplements are available without a prescription, proper dosing is important for maximum benefit and to avoid possible complications.

Read on to learn more about calcium carbonate, how it can benefit you, recommended dosage, and potential side effects.

Calcium carbonate is a type of naturally occurring calcium salt that is often used as a food additive, an antacid, a phosphate binder, or a dietary supplement.

As a pharmaceutical product, it can be helpful for:

Calcium carbonate supplements come in tablet, chewable, oral suspension, or powder form. Your body can get the most calcium from calcium carbonate in powder form, but other forms are also effective.

Calcium carbonate has several medical uses. While it’s most widely known as an antacid, it is also used to help manage or prevent the following conditions:

  • Low calcium levels (hypocalcemia): Calcium carbonate is a common ingredient in calcium supplements. Chronically low calcium levels in the blood can be the result of such conditions as osteoporosis, hypothyroidism, and hypoparathyroidism.
  • GERD and heartburn: The antacid properties of calcium carbonate can relieve symptoms of digestive issues, such as acid indigestion and heartburn. Calcium carbonate offers relief by neutralizing the stomach acids that cause these symptoms.
  • Chronic kidney disease: Calcium carbonate acts as a phosphate binder, which may help prevent bone disorders in people with kidney disease.
  • Preeclampsia: Calcium supplements can help reduce the risk of high blood pressure (preeclampsia) during pregnancy.

Calcium carbonate is generally considered safe to take as a daily calcium supplement.

But if you find you are regularly taking calcium carbonate to relieve digestive issues, a doctor can help you investigate the root cause of your concerns. Chronic antacid use or misuse may lead to negative health effects.

The dosage recommendations for calcium carbonate depend on your specific health needs. Experts typically suggest a daily dose of no more than 500 milligrams (mg) of supplemental calcium carbonate, as this is the most beneficial amount for absorption.

A doctor might recommend short-term use of higher dose calcium carbonate (up to 1,000 mg), but you should not take more than 8 grams daily during that time period.

Precautions to be aware of

Calcium carbonate is typically well tolerated. Yet you may need to have your calcium carbonate intake closely monitored if you have or are at risk of:

While not conclusive, some studies have shown calcium to increase the risk of heart attack and, possibly, prostate cancer.

Storage and disposal recommendations

If you’re taking calcium carbonate, be sure to follow these storage and disposal suggestions:

  • Store it at room temperature, away from high heat and moisture.
  • Keep it in its original container.
  • Ensure that it is out of reach of children and pets.
  • Do not flush any unused calcium carbonate down the toilet.
  • If possible, use a regional medication take-back program to dispose of any unneeded medication.
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Side effects of calcium carbonate are usually minor and short term. If you experience any of these side effects for an extended period of time, let your doctor know:

  • nausea or stomach upset
  • vomiting
  • belching or bloating
  • stomach pain
  • constipation
  • loss of appetite
  • metallic taste
  • increased urination
  • dry mouth

Calcium carbonate supplements are an effective way to increase your calcium levels if you don’t get enough through your diet or have a condition that leads to lower calcium in your body.

Calcium carbonate is also useful as an antacid to manage the symptoms of several digestive issues and as a phosphate binder for people with chronic kidney disease.

While the side effects of calcium carbonate are generally mild, it’s important to take only the recommended dose to prevent any unexpected health outcomes.