Which Type of Calcium Supplement Is Best?

Question: Which type of calcium supplement is best?

Answer: There are many types of calcium supplements, including calcium carbonate, calcium citrate, calcium gluconate, and others. Calcium exists as a compound, bound to something else, that's why it is found in these forms. However, some people debate whether or not one particular type of calcium is better than another.

Benefits of calcium supplements
Verywell / JR Bee

The Best Calcium Supplements

The most important thing to look for when choosing a calcium supplement is the amount of elemental calcium the supplement contains. Depending on the manufacturer, the amount of elemental calcium may be listed directly on the label, or the weight may be listed on the calcium tablet itself.

Another way to check for the amount of elemental calcium the supplement contains is by looking at the recommended daily allowance (RDA). The RDA for most individuals is 1000 milligrams (mg) of calcium per day (this varies by age, gender, and special situations, including pregnancy). If the bottle states a tablet contains 40% of the RDA of calcium, then it contains 400 mg of elemental calcium.

Calcium Carbonate vs Calcium Citrate

Calcium supplements are generally made with one of two sources of elemental calcium: calcium carbonate or calcium citrate. There are several differences to note:

Calcium Carbonate
  • Contains the highest concentration of elemental calcium at 40% by weight

  • Tablets are often smaller and fewer are needed to meet the RDA

  • Shouldn't be taken on an empty stomach or if you have low stomach acid

  • Can cause bloating or constipation

  • Tends to be the least expensive

  • Possible side effects include: nausea/vomiting, belching, dry mouth, increased urination, metallic taste, fatigue, bone pain

Calcium Citrate
  • Contains the second highest concentration of elemental calcium at 21% by weight

  • Tablets are often bigger and more are needed to meet the RDA

  • Absorbs well when taken without food and is good for people on antacids

  • Doesn't constipate and is better for people with digestive issues

  • Can be more expensive

  • Possible side effects include: nausea/vomiting, belching, low blood pressure, headache, increased urination, loss of appetite, fatigue

Most people do not experience side effects when taking the RDA for calcium supplements. Contact your healthcare provider if side effects are severe or do not go away, as this could mean you have too much calcium in your system.

Although rare, allergic reactions can occur. Seek medical attention if you develop symptoms of an allergic reaction, such as a rash or hives; wheezing; difficulty breathing, swallowing, or talking; tightness in your chest; or swelling of the face, mouth, throat, or lips.

How to Take Calcium Supplements

There are limits on how much calcium your body can absorb at once, and other foods and medications can impact calcium absorption. Here are some tips on taking your calcium to maximize its benefits:

  • Meals: Different types of calcium vary in whether they're absorbed best with or without food. Calcium carbonate should be taken with meals. Calcium citrate should be taken on an empty stomach.
  • Medications: Calcium should not be taken with certain medications, including antibiotics, iron supplements, high blood pressure medications, and others. Calcium can bind to these medications and diminish their absorption. Check with your pharmacist about medication interactions.
  • Vitamin D: Calcium is best absorbed when taken with vitamin D. Many supplements are produced with both calcium and vitamin D included.
  • Dose: Calcium should be taken in divided doses, rather than all at once. Separate doses into twice or three times daily for optimal absorption.

How to Choose the Supplement for You

While you should avoid oyster shell calcium, there are positives and negatives to both calcium carbonate and calcium citrate. Read the recommendations for when a supplement you are considering should be taken, and consider if that fits into a reasonable schedule for you. Look at the amount of elemental calcium contained in the supplement to ensure you would be consuming an adequate dose.

Frequently Asked Questions

Do calcium supplements contain toxic levels of lead?

Some supplements do contain potentially dangerous levels. Those made from unrefined oyster shell, bone meal, or dolomite tend to have especially high levels of lead. Instead, look for calcium that has the United States Pharmacopeia (USP) verification symbol, a sign that levels are acceptable.

What type of calcium supplement can lower my risk of kidney stones?

Calcium citrate is recommended for people at risk for kidney stones. This supplement helps you excrete more urinary citrate, which protects against the formation of stones.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium. Dietary Reference Intakes for Calcium and Vitamin D. National Academies Press.

  2. National Institutes of Health Office of Dietary Supplements. Calcium fact sheet for health professionals.

  3. Wiria M, Tran HM, Nguyen PHB, Valencia O, Dutta S, Pouteau E. Relative bioavailability and pharmacokinetic comparison of calcium glucoheptonate with calcium carbonatePharmacol Res Perspect. 2020 Apr;8(2):2. doi:10.1002/prp2.589

  4. Watson J, Lee M, Garcia-Casal MN. Consequences of inadequate intakes of vitamin A, vitamin B12, vitamin D, calcium, iron, and folate in older personsCurr Geri Rep. 2018 Apr;7(2):103-113. doi:10.1007/s13670-018-0241-5

  5. U.S. Preventive Services Task Force. Vitamin D, calcium, or combined supplementation for the primary prevention of fractures in community-dwelling adults: Preventive medication.

  6. National Institutes of Health Office of Dietary Supplements. Calcium consumer fact sheet.

  7. MedlinePlus. Calcium supplements.

  8. Frassetto L, Kohlstadt I. Treatment and prevention of kidney stones: An update. Am Fam Physician. 2011 Dec 1;84(11):1234-1242.

By Jonathan Cluett, MD
Jonathan Cluett, MD, is board-certified in orthopedic surgery. He served as assistant team physician to Chivas USA (Major League Soccer) and the United States men's and women's national soccer teams.