Calcium citrate or calcium carbonate
| Form | Calcium in the salt | Taking it |
|---|---|---|
| Calcium carbonate | about 40% | Best taken with a meal, because it needs stomach acid to dissolve (NIH ODS) |
| Calcium citrate | about 21% | Absorbed equally well with or without food (NIH ODS) |
The percentage is why a citrate product needs more powder or more capsules for the same calcium. The label always states elemental calcium, so compare that number, not the weight of the salt.
Reading the dose
The EU reference intake (NRV) for calcium is 800 mg.
| Calcium per dose | % of NRV (800 mg) |
|---|---|
| 350 mg | 44% |
| 400 mg | 50% |
| 600 mg | 75% |
| 700 mg | 88% |
EFSA set a tolerable upper intake level of 2500 mg a day for adults, counting food and supplements together. Supplements in this category stay far below it. NIH ODS notes that the body absorbs calcium best in amounts of up to about 500 mg at a time, which is why the Swanson capsules are taken one at a time, twice a day.
Calcium products compared
| Product | Form | Daily dose | Calcium | Pack lasts |
|---|---|---|---|---|
| NOW Foods Calcium Carbonate Powder, 340 g | calcium carbonate | 1/2 level teaspoon, with a meal | 600 mg (75%) | see price per day on the card |
| Swanson Calcium Citrate 200 mg, 60 capsules | calcium citrate | 1 capsule twice a day with meals | 400 mg (50%) | 30 days |
| Swanson Calcium Citrate Powder, 227 g | calcium citrate, dairy-free | 1 or 2 scoops (1.67 g each), with a meal | 350 or 700 mg (44 or 88%) | about 68 to 135 days |
Mix the NOW Foods powder into juice such as tomato or orange. Swanson advises mixing its powder into a drink, milk or juice, and not with water alone. The Swanson powder pack contains a freshness sachet that must not be eaten.
Calcium with vitamin D and magnesium
Calcium rarely travels alone. Vitamin D has its own authorised claim: vitamin D contributes to normal absorption/utilisation of calcium and phosphorus. You will find it in vitamin D, and magnesium is the other mineral people most often combine with calcium. Add up the amounts if a multivitamin also contains calcium.
Calcium benefits under EU-authorised claims
Regulation (EU) No 432/2012 permits these statements for products that provide at least 15% of the NRV per daily dose. Every product in this category meets that condition:
- Calcium contributes to normal blood clotting.
- Calcium contributes to normal energy-yielding metabolism.
- Calcium contributes to normal muscle function.
- Calcium contributes to normal neurotransmission.
- Calcium contributes to the normal function of digestive enzymes.
- Calcium has a role in the process of cell division and specialisation.
- Calcium is needed for the maintenance of normal bones.
- Calcium is needed for the maintenance of normal teeth.
Calcium in food
According to NIH ODS, dairy products are the main source for most people, followed by calcium-fortified plant drinks and some leafy greens. A supplement fills the gap between what you eat and 800 mg, so it helps to know your typical day before choosing a dose.
Questions
Citrate or carbonate?
Citrate does not depend on a meal, carbonate should be taken with one. Carbonate holds more calcium per gram. Choose by the calcium per dose and the price per day.
How much calcium at once?
NIH ODS says absorption is best up to about 500 mg at a time. The products here already divide or limit the dose that way, so follow the label.
Is the powder dairy-free?
The Swanson calcium citrate powder is labelled dairy-free. Calcium carbonate is a mineral salt, not a dairy product.
Who should ask a doctor first?
NOW Foods advises talking to a doctor if you are pregnant, breastfeeding, ill or taking medicines. Swanson does not recommend its powder for pregnant or breastfeeding women. If you take medicines, ask a pharmacist whether timing matters.
Can I take calcium every day?
Within the daily dose on the label, yes. Do not combine several calcium products without adding up the amounts.
Sources
- Regulation (EU) No 1169/2011, Annex XIII (reference intakes)
- Regulation (EU) No 432/2012 (permitted health claims)
- NIH Office of Dietary Supplements: Calcium fact sheet
- EFSA (2012): Scientific opinion on the tolerable upper intake level of calcium
Content reviewed by Inese Kalniņa, dietitian.
2026-07-21