Calcium Carbonate (e.g. Tums®)

Last Update: 03 Jul 2026

Table of content

1. What is it? 2. What are the risks according to research? 3. Breastfeeding/ chestfeeding 4. What about fathers and sperm donors? 5. Key points

Welcome to our fact sheet on calcium carbonate during pregnancy and lactation. This information is based on available published literature. It should not take the place of medical care and advice from your healthcare provider.

The HEALTHY PREGNANCY HUB team is collaborating with MotherToBaby to share information on this topic. The original version is available here (October 2025).

Serene, our chatbot, can also answer your questions about medications during pregnancy.

Please note that this fact sheet is based on United States information and has been adapted for Canada, with a review by our Canadian experts. Minor differences may exist between the two countries. Always consult your healthcare professional for information tailored to your situation.

1. What is calcium carbonate?

Calcium carbonate is a dietary supplement that has been used as an antacid to help symptoms of heartburn, acid indigestion, and upset stomach. Some examples of over-the-counter antacids with calcium carbonate are Tums®, Rolaids®, Maalox®, and Mylanta®.  

The supplement label should list both the calcium carbonate dose along with the actual calcium dose, which is often listed as ‘elemental calcium’. There are Recommended Daily Allowance (RDA) guidelines and upper limit amounts for calcium (elemental calcium). 

If you are pregnant and/or lactating and age 19 or older, the RDA is 1,000 mg a day, and the upper limit is 2,500 mg. If you are pregnant and/or lactating and are ages 14 to 18 years old, the RDA of calcium is 1,300 mg a day and the upper limit is 3,000 mg. 

People can reach their RDA of calcium from the foods and beverages they consume as well as the calcium found in supplements and vitamins. For example, 1 cup of milk or 1.5 inches of hard cheese, provides approximately 300 mg. If you have a medical condition that might change your calcium levels, talk with your healthcare providers about the amount of calcium that is right for you.  

2. What does research say about the safety during pregnancy?

I take calcium carbonate. Can it make it harder for me to get pregnant? 

When used as directed and within the recommended amounts, taking calcium carbonate is not expected to make it harder to get pregnant. 

Does taking calcium carbonate increase the chance of miscarriage? 

Miscarriage is common and can occur in any pregnancy for many different reasons. When used as directed and within the recommended amounts, taking calcium carbonate is not expected to increase the chance of miscarriage. 

Does taking calcium carbonate increase the chance of birth defects? 

Birth defects can happen in any pregnancy for different reasons. Out of all babies born each year, about 3 out of 100 (3%) will have a birth defect. We look at research studies to try to understand if an exposure, like calcium carbonate, might increase the chance of birth defects in a pregnancy. When used as directed and within the recommended amounts, calcium carbonate is not expected to increase the chance of birth defects above the background risk. 

Does taking calcium carbonate in pregnancy increase the chance of other pregnancy-related problems? 

When used as directed and within the recommended amounts, taking calcium carbonate is not expected to increase the chance of other pregnancy-related problems such as preterm delivery (birth before week 37) or low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth). 

Does taking calcium carbonate in pregnancy affect future behavior or learning for the child?  

Studies have not been done to see if calcium carbonate can cause behavior or learning issues for the child.  

What if I take more than the recommended amounts of calcium carbonate? 

The use of calcium carbonate in more than recommended amounts might increase the chance of low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth). There have been a few case reports of newborns with seizures when high doses of calcium carbonate were used near the end of pregnancy. Also, taking more calcium carbonate than recommended can cause milk-alkali syndrome, a condition in which there is a high level of calcium in the body (hypercalcemia) and could lead to kidney failure or inflammation of the pancreas in the person who is pregnant. 

3. Lactating while taking calcium carbonate

Calcium is found in human milk. When used as directed and within the recommended amounts, calcium carbonate is unlikely to be harmful to a nursing baby. Be sure to talk to your healthcare provider about all your breast/chest feeding questions.

4. What about fathers and sperm donors?

If a male takes calcium carbonate, could it affect his fertility or increase the chance of birth defects? 

Studies have not been done to see if calcium carbonate could affect male fertility (ability to get a person pregnant) or increase the chance of birth defects. In general, exposures that fathers and sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures here.

Key points

Calcium carbonate (e.g. Tums®) is a supplement commonly used to relieve heartburn and acid reflux.
When taken at recommended doses, calcium carbonate has no known risk of miscarriage, birth defects, or other pregnancy complications.
Calcium naturally passes into breast milk, and calcium carbonate is considered safe for the baby when taken as recommended.
Taking too much calcium carbonate can cause health problems for the pregnant person.
Always talk with a healthcare professional before changing or stopping any medication.

References

Please click here for references.

Disclaimer

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