Osteoporosis Home > Calcium Side Effects

Constipation, belching, and gas are some of the bothersome side effects that have been reported with calcium. Side effects of the supplement are usually not dangerous, but calcium toxicity can occur with very high dosages. Some of the potentially serious side effects of calcium that should be reported to your healthcare provider include excessive drowsiness, frequent urination, and nausea or vomiting.

An Overview of Calcium Side Effects

Although it is a fairly "safe" dietary supplement, calcium can cause some side effects. In fact, many people stop taking calcium (or take it less often than they should) due to bothersome side effects. While most side effects of calcium are not dangerous, calcium toxicity can occur, especially with very high dosages.
(This article covers many, but not all, of the possible side effects with calcium. Your healthcare provider can discuss a more complete list of side effects with you.)

Possible Side Effects of Calcium

Reported calcium side effects that are bothersome (but usually not dangerous) include:
Although constipation is considered a classic side effect, there is surprisingly little scientific evidence to suggest that calcium really causes constipation.

Serious Side Effects

Some possible side effects of calcium are more serious and should always be reported to your healthcare provider. These side effects include:
  • Kidney stones
  • Excessive drowsiness
  • Muscle weakness
  • Nausea and vomiting
  • Frequent urination
  • Changes in your heart rate
  • Confusion
  • Signs of an allergic reaction, such as:


    • Hives or a rash
    • Itching
    • Swelling of the lips, mouth, or throat
    • Wheezing or other difficulty breathing.


Although an allergy to calcium would be highly unlikely (since calcium is found naturally throughout the human body), it is possible for people to be allergic to inactive ingredients in calcium supplements.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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