Calcium Citrate Tetrahydrate

Calcium

Highly bioavailable calcium form; does not require stomach acid for absorption.

Part of Calcium Minerals
Compare all forms

Typical dose

500-1000 mg of calcium citrate (providing ~105-2...

Oral Oral safety: low

About this supplement

Calcium Citrate Tetrahydrate is a specific hydrated form of calcium citrate, a calcium salt of citric acid. It contains four water molecules per formula unit, making it a stable crystalline hydrate. This form is widely used in dietary supplements and fortified foods due to its excellent bioavailability, particularly in individuals with low stomach acid or those taking acid-reducing medications. Unlike calcium carbonate, it does not require stomach acid for absorption, making it suitable for older adults and those with digestive issues. The tetrahydrate form provides approximately 21% elemental calcium by weight. It is considered one of the most bioavailable and well-tolerated calcium supplements available.

How much to take

Typical amount
500-1000 mg of calcium citrate (providing ~105-210 mg elemental calcium) per day, often divided into two doses to enhance absorption.
Suggested range
500-1200 mg daily (as calcium citrate)

Potential benefits

Benefits linked to this supplement form:

Bone Health

Research strength: Very strong

 Muscle Function

Research strength: Very strong

 Cardiovascular Health

Research strength: Strong

 Bone Health Support

Research strength: Very strong

 Bone Health & Osteoporosis Prevention

Research strength: Very strong

 Nerve Transmission

Research strength: Very strong

 Improved Absorption in Low Acid Conditions

Research strength: Very strong

Things to watch for

Possible side effects linked to this form:

Hypercalcemia

How serious: Severe

 Constipation

How serious: Mild

 Kidney Stones

How serious: Moderate

 Gas and Bloating

How serious: low

Health goals

Needs and goals this form may help with:

Other forms of Calcium

Compare absorption and active amounts with sibling forms:

Calcium
Calcium 2-aminoethylphosphate
Calcium acetate
Calcium alpha-ketoglutarate
Calcium alpha-ketoisocaproate
Calcium Arginine alpha-ketoisocaproate
Calcium Ascorbate
Calcium Beta-Hydroxybutyrate
Calcium Bisphosphonate
Calcium borate
Calcium borogluconate
Calcium Carbonate
Calcium Caseinate

Slow-digesting milk protein; provides sustained amino acid release.
Calcium Citrate
Calcium Citrate (anhydrous)

Highly bioavailable calcium form; does not require stomach acid for absorption.
Calcium Citrate Malate

Highly absorbable calcium source; often used in fortified foods.
Calcium d-Glucarate
Calcium Folinate
Calcium Formate
Calcium fructate
Calcium Fructo-Oligosaccharides
Calcium Fructoborate
Calcium fructopyranose borate
Calcium Glycerol Gluconate
Calcium hydroxycitrate
Calcium hydroxyisopcaproate
Calcium hydroxymethylbutyrate
Calcium Iodide
Calcium leucine alpha-ketoisocaproate
Calcium Magnesium Butyrate
Calcium Magnesium Citrate
Calcium magnesium phytate
calcium Octanoate
Calcium Oligofructose
Calcium Palmitate
Calcium pangamate
Calcium Phosphate
Calcium phytate
Calcium Potassium Phosphate Citrate
Calcium pyruvate
Calcium Silicate
Calcium Stearate
Calcium sulfide
Calcium tartrate
Potassium Caseinate

Slow-digesting milk protein; often used in shakes and medical foods.
Sodium Caseinate

Slow-digesting milk protein; common in meal replacements and medical nutrition.
Compare all forms in the table
Technical details â–¼

Chemical ID (CAS)

5785-44-4

Formula

Ca3(C6H5O7)2·4H2O

Physical properties

White, fine, crystalline powder. Odorless. Slightly hygroscopic. Soluble in dilute hydrochloric and nitric acids, slightly soluble in water, practically insoluble in ethanol. The tetrahydrate form is stable under normal storage conditions.

How it’s made

Typically produced synthetically by reacting citric acid with a calcium source (such as calcium carbonate or calcium hydroxide) in an aqueous solution, followed by crystallization under controlled conditions to yield the tetrahydrate form. The process involves purification, filtration, drying, and milling to achieve the desired particle size.