Calcium Carbonate vs Calcium Citrate: Which Form Suits You? (Canada)

Short answer: calcium carbonate is best taken with food, while calcium citrate can be taken with or without food and is the form usually suggested for people with low stomach acid. Either way, your body absorbs calcium best in amounts of 500 mg or less at one time, so the number of doses and the elemental calcium on the label matter more than the form's name. Count the calcium you get from food first, because many people need less from supplements than they think.

Carbonate vs citrate at a glance

Our product pages also list Jamieson Mega Cal 650 mg, a mini-tab caplet with 650 mg of calcium per caplet. Check the label for its calcium source. Its page notes that calcium is absorbed best in doses of 500 to 600 mg or less at a time, so larger daily amounts should be spread across meals.

Elemental calcium: read the right number

Calcium compounds are calcium bound to something else (carbonate or citrate), so the weight of the compound is not the weight of calcium you receive. The Canadian label lists the elemental calcium per tablet. The Webber carbonate label states 500 mg of elemental calcium per tablet, while the citrate product is named for 300 mg, so compare the elemental amount on each label before working out how many tablets give you the amount your health professional recommends.

Canadian angle: DRIs, NPNs and vitamin D

Health Canada's Dietary Reference Intakes list the recommended amount (RDA) and the tolerable upper intake level for calcium by age, sex, pregnancy and breastfeeding; use the Canadian table linked in the sources rather than a U.S. one. The upper level covers calcium from food and supplements together. Calcium supplements are licensed as natural health products, so look for the NPN on the label and look it up in the Licensed Natural Health Products Database (our NPN guide shows how). The Webber carbonate page also notes that calcium works best alongside adequate vitamin D; see Vitamin D in Canada for the Canadian figures.

Who it may not suit, and interactions

• Kidney stones or kidney disease. The Webber and Jamieson product pages advise talking to a health professional before use if you have kidney disease or a history of kidney stones.
• Other medicines. The Jamieson Mega Cal page says calcium can interfere with thyroid medicines, some antibiotics, iron and osteoporosis medicines, and advises taking them a few hours apart. The Webber pages give similar warnings.
• Iron. Health Canada advises waiting 1 to 2 hours after a meal before taking calcium supplements if you want to improve iron absorption. See our iron forms guide.
• High total intake. Webber's citrate page cautions about high calcium intake from multiple supplements, including multivitamins and antacids that contain calcium.
• Pregnancy and breastfeeding. Ask a health care practitioner about the right amount.

Health Canada's multi-vitamin/mineral monograph lists calcium carbonate and calcium citrate among the permitted calcium sources, so both forms can be licensed for sale in Canada. We could not open the monograph's calcium caution wording directly, so rely on the label of the exact product you buy.

Practical tips for taking calcium

• Use the label directions. The Webber carbonate page says to swallow the tablet with a full glass of water and take it with food. The citrate page also suggests taking it with meals and dividing the total daily amount into smaller doses when a higher intake is needed.
• Keep a schedule. Both pages stress consistent daily use rather than occasional doses.
• Combine with the basics. Balanced nutrition, weight-bearing activity and adequate vitamin D are part of any bone-health routine, as the Webber page notes.
• Store it properly. Keep tablets in a cool, dry place and out of children's reach.

How to choose

1. Tally your calcium from dairy, fortified plant drinks, canned fish with bones, leafy greens and your multivitamin.
2. If you have low stomach acid, ask your pharmacist whether citrate suits you better. If you will take it with meals, carbonate works.
3. Split the daily amount so no single dose goes beyond about 500 mg.
4. Drink water, and speak to a pharmacist if constipation persists.

See the full range in our Minerals collection.

When to see a doctor or pharmacist

• Before starting calcium if you have kidney disease, kidney stones, high blood calcium or a parathyroid condition.
• If you take thyroid medicine, antibiotics, osteoporosis medicine or iron: ask about timing.
• For severe stomach pain, persistent nausea or constipation that does not settle.
• If you are worried about bone health, a doctor can discuss testing and a plan that goes beyond supplements.

Sources

• Health Canada. Multi-Vitamin/Mineral Supplements monograph (permitted calcium sources).
• Health Canada. Dietary Reference Intakes tables: elements table (calcium).
• Health Canada. Iron (timing of calcium supplements).
• NIH Office of Dietary Supplements (U.S.; background). Calcium: Fact Sheet for Health Professionals and Fact Sheet for Consumers (carbonate with food; citrate with or without; 500 mg or less at a time).
• Product details: the Canadian product pages linked above (Webber Naturals, Jamieson).

This guide is general information, not medical advice. Ask your pharmacist or doctor about your own situation.