Calcium Citrate
Also known as: tricalcium citrate, calcium citrate tetrahydrate, Ca citrate
A calcium salt of citric acid that does not rely on stomach acid to dissolve, so it can be taken with or without food and is often chosen for older adults and people on acid-reducing medication. It carries about 21% elemental calcium, roughly half the density of carbonate, which means more tablets or capsules for the same dose. A meta-analysis found it is absorbed somewhat better than carbonate on a per-milligram basis.
Research summary
Supplies calcium for skeletal mineralization and cellular signaling; the citrate anion keeps calcium soluble across a range of gastric pH.
Dosage
Daily amounts, elemental (21% of the compound is the element).
| Lowest studied | Typical range | Highest studied | Upper limit |
|---|---|---|---|
| 200 mg | 200–500 mg | 1,000 mg | 2,000 mg |
NIH ODS — UL is 2,500 mg/day for adults 19–50 and 2,000 mg/day for adults 51+; the app uses the lower adult value (total intake from food plus supplements)
Doses are elemental calcium. Can be taken with or without meals. Splitting into 500 mg or smaller doses improves fractional absorption. Studies have used up to about 1,000 mg/day supplemental calcium as citrate. The tetrahydrate is about 21% calcium; anhydrous tricalcium citrate is closer to 24%, so confirm which grade the supplier ships.
Source material: synthetic (citric acid reacted with calcium carbonate)
As supplied: Tetrahydrate ≈ 21% Ca; anhydrous ≈ 24% Ca
Forms of Calcium
| Form | Typical dose | Element % | Formats | Price |
|---|---|---|---|---|
| Calcium Citrate | 200–500 mg | 21% | Capsule, Powder, Tablet, Gummy, Liquid | low |
| Calcium Carbonate | 250–600 mg | 40% | Capsule, Powder, Tablet, Gummy, Liquid | low |
| Calcium Citrate Malate | 250–500 mg | 23% | Capsule, Powder, Tablet, Liquid | mid |
| Calcium (Microcrystalline Hydroxyapatite, MCHC) | 250–700 mg | 24% | Capsule, Powder, Tablet | high |
Format suitability
- Capsule
- Powder
- Tablet
- Softgel
- Gummy
- Liquid
Bulky: 500 mg elemental needs about 2,400 mg of compound, which is three to four size-00 capsules or a large tablet. Powder and liquid formats are practical for higher doses. Mild sour note works well in flavored powders.
Formulation notes
Separate from iron, zinc, and thyroid hormone. Citrate raises aluminum absorption, which matters for people taking aluminum-containing antacids. Pairs with vitamin D3 and magnesium in bone formulas.
- Has an upper limit
Sources
Related ingredients
Calcium Carbonate
MineralThe most concentrated and least expensive common calcium salt, supplying about 40% elemental calcium by weight.
Typical: 250–600 mg
Vitamin D3 (Cholecalciferol)
VitaminThe form of vitamin D the body makes from sunlight and the most effective supplemental form for raising blood levels.
Typical: 1,000–2,000 IU
Folic Acid
VitaminFolic acid is the fully oxidized, synthetic form of folate used in food fortification and most supplements.
Typical: 400–800 mcg
Magnesium Oxide
MineralThe most concentrated magnesium source at about 60% elemental magnesium, which is why it dominates in multivitamins and small tablets.
Typical: 200–350 mg
Iron Bisglycinate
MineralFerrous iron chelated with two glycine molecules, the form most prenatal and gentle-iron products now use.
Typical: 18–30 mg