Benefits, Side Effects, and More

Calcium carbonate is a type of calcium supplement used to treat low blood calcium levels and calcium-related conditions such as osteoporosis (weak and brittle bones). As an antacid, it can lower stomach acidity and relieve heartburn.

Calcium carbonate is a common food additive. It can be found in cereals, dairy products, packaged broths, and other foods. As a supplement, calcium carbonate is generally used short-term in small doses, as high doses can cause serious side effects.

Calcium carbonate can help treat low blood calcium levels and calcium-related conditions, such as osteoporosis, hypothyroidism (low thyroid hormones), hypoparathyroidism (low parathyroid hormones), and rheumatoid arthritis (an autoimmune disease affecting the joints).

Parathyroid hormone (PTH) and calcitonin, a thyroid hormone, regulate blood calcium levels. When blood calcium levels increase or decrease, these hormones tell the kidneys to excrete or absorb more calcium to keep levels stable. People with conditions affecting hormones or kidney health may need calcium supplementation.

People taking certain medications that cause calcium loss may need calcium supplements to maintain normal calcium levels. Some medications include loop diuretics (medications that excrete excess fluids), bisphosphonates (medications that prevent bone loss), calcitonin (a hormone that regulates blood calcium levels), and corticosteroids.

Calcium is a mineral with a key role in bone formation, muscle function, nerve transmission (carrying messages between brain cells), hormone production, and more.

Most calcium is found in the bones. Calcium deficiency is linked to bone diseases. One of the most common bone diseases, osteoporosis, involves the loss of bone mineral content. When bone mineral content decreases, the bones become weaker and the risk of fractures increases.

Calcium carbonate can help treat and manage bone-related conditions, including osteoporosis.

Calcium carbonate is an antacid, a type of medication that neutralizes stomach acid. Stomach acid can cause heartburn, which is a burning feeling in your chest or throat.

Heartburn is a common symptom in conditions like gastroesophageal reflux disease (GERD), where stomach acid travels up to the throat. Stomach and duodenal ulcers, which are open sores in the lining of the stomach and the first part of the small intestine, can cause heartburn.

Phosphate is another mineral. Calcium carbonate binds to phosphate in the small intestine, benefiting people who need to limit their phosphate absorption.

People with chronic kidney disease can develop high blood phosphate levels because their kidneys cannot remove the mineral through urine. Excess phosphate in the blood can lead to bone and heart problems. A healthcare provider can prescribe calcium carbonate to lower the body’s phosphate absorption and avoid complications of high phosphate levels.

Calcium carbonate is used in the food industry as an additive called E170. Some foods that can contain calcium carbonate include:

• Breakfast cereals 
• Dairy products
• Noodles
• Dried fruits and vegetables
• Nut butters
• Cocoa and chocolate products
• Seasoning and condiments 
• Soup and broths

Other forms of calcium used in the food industry and pharmaceuticals include calcium citrate, calcium phosphate, calcium lactate, and calcium gluconate.

Food sources of calcium include:

• Low-fat yogurt: 415 milligrams (mg) per 8 ounces, 32% of the Daily Value (DV)
• Sardines: 325 mg per 3 ounces, 25% of the DV
• Non-fat milk: 299 mg per 1 cup, 23% of the DV
• Cottage cheese: 138 mg per 1 cup, 11% of the DV
• Soybeans: 131 mg per ½ cup cooked, 10% of the DV

Calcium carbonate is available in chewable, tablet, powder, and oral liquid forms. If you take a tablet, drink a glass of water with it.

Dosage 

The dosage for calcium carbonate varies depending on your age, health conditions, weight, hormone levels, and stomach acidity. 

When taking calcium carbonate as a supplement, use the recommended dietary intake (RDI) for calcium as a guideline. The RDI for adults aged 19-50 is 1,000 milligrams of calcium. About 400 milligrams of elemental calcium is in every 1,000 milligrams of calcium carbonate. Adults can safely take up to 2,500 milligrams of calcium carbonate as a supplement.

It’s important to follow your healthcare provider’s dosage recommendations. Individuals who have gone through menopause, adults over 50, pregnant and breastfeeding people, and teens aged 9-18 need more calcium than the RDI for adults aged 19-50.

Calcium carbonate is best absorbed when taken 500 milligrams or less at a time, so it is recommended to divide the daily dosage. For example, if you take 1,000 milligrams, take half the dose twice daily.

Do not use calcium supplements without the approval of your healthcare provider, especially if you have health conditions, such as kidney disease, endocrine (hormone-related) disorders, a history of heart failure, or if you’re pregnant or breastfeeding.

Calcium carbonate is generally considered safe by the U.S. Food and Drug Administration (FDA). However, you should consult your healthcare provider before using calcium carbonate if you have:

• Sensitivity to calcium carbonate
• Kidney stones
• High levels of calcium in your urine or blood
• Low levels of phosphate in your blood
• Very low stomach acid

Potential Drug Interactions

Some medications can decrease the absorption of calcium carbonate. To ensure effective use, avoid taking these medications at the same time as calcium carbonate. If you’re using any of the following drugs, talk to your healthcare provider before taking calcium carbonate:

• Histamine-2 Receptor Blockers: Medications used to treat various gastrointestinal conditions. Examples include Pepcid (famotidine), Tagamet (cimetidine), and Axid (nizatidine).
• Steroids: These are used to treat a wide range of conditions, including autoimmune diseases, asthma, and skin conditions.
• Thiazide Diuretics: These medications are used to manage edema and affect blood calcium levels. Examples include Esidrix (hydrochlorothiazide) and Lozol (indapamide).

Calcium carbonate reduces stomach acidity, which can make it harder for your body to absorb and use some other medications. These include:

• Bisphosphonates (medications to treat loss of bone mass)
• Fluoroquinolones (antibiotics)
• Tetracyclines (antibiotics)
• Proton Pump Inhibitors (medicines that reduce stomach acid)
• Anti-arrhythmic drugs (medications to treat heart rhythm conditions)
• Thyroid Hormones
• Iron

Additionally, taking vitamin D can help increase the absorption of calcium carbonate, making it more effective.

Can You Take Too Much?

It is possible to take too much calcium carbonate. The short-term maximum dose is 8-10 grams per day. However, long-term use of lower doses (more than 2 grams) can cause adverse effects such as high blood calcium levels, low blood phosphate levels, kidney stones, and kidney damage.

Calcium carbonate is generally used in small doses, short-term, and periodically. Most side effects are minor, but an overdose of calcium carbonate supplementation can cause:

• Irregular heart rhythms
• Muscle twitching
• Abdominal pain
• Bone pain
• Acute renal failure
• Kidney stones
• Gallstones
• Coma
• Confusion

Calcium carbonate is a type of calcium supplement and antacid. It’s used as a food additive in smaller amounts. Calcium carbonate is mainly used to treat low blood calcium levels, bone-related diseases, heartburn, and high blood phosphate levels.

Calcium carbonate can also interact with medications and worsen some conditions. It’s important to consult your healthcare provider before using calcium carbonate.