Dicalcium phosphate

Grades and forms

Dicalcium phosphate (calcium hydrogen phosphate, CaHPO4) contains 29.5 % calcium on an anhydrous basis, so 339 mg of powder delivers 100 mg of calcium. Supplement manufacturers use it in two roles: as a calcium and phosphorus source, and as a filler in tablets and capsules. The role decides the grade you buy.

The material is traded as the anhydrous salt and as the dihydrate (CaHPO4·2H2O). The identifiers and figures on this page refer to the anhydrous form. The dihydrate carries water of crystallisation, so it contains less calcium per gram. Recalculate the label claim from the certificate of analysis if you switch between them.

Physical form matters as much as hydrate state. Fine powder grades suit blending, capsule filling and wet granulation. Coarser granular grades are designed for direct compression, where flow and compactibility count more than fineness. Assay, particle size distribution and bulk density are stated on the specification sheet.

SoleChem sends the specification sheet and certificate of analysis with its quote. State the hydrate, physical form and grade you need in the quote form.

EU regulatory status

Calcium salts of orthophosphoric acid are listed in Annex II of Directive 2002/46/EC as a substance that may be used in food supplements. Calcium and phosphorus both appear in Annex I of the same Directive. The guide to permitted forms explains how the two annexes work together.

Calcium phosphates are also authorised food additives in the E341 group under Regulation (EC) No 1333/2008. Check the purity criteria for E341 in Regulation (EU) No 231/2012. Confirm the exact sub-designation and the conditions of use in food supplements before you label a filler use.

The EU has not set harmonised maximum levels for calcium in food supplements. Member states apply their own limits, and these may also cover phosphorus. The maximum levels guide explains how national rules differ.

Formulation notes

Dicalcium phosphate is practically insoluble in water. It suits tablets, capsules and powder blends, but not clear drinks or liquid shots. In suspended or reconstituted powders it gives a chalky mouthfeel and settles out.

In tablets it is a long-established direct-compression filler. It fragments under compression, which helps tablet strength without heavy binder loads. The dihydrate can lose water when heated during drying or coating, which may change tablet hardness and weight. Check process temperatures against the grade before scale-up.

For capsules, whether a calcium claim fits one shell depends on the bulk density on the specification sheet and the capsule size. Calcium salts are bulky per milligram of element, so higher claims usually need tablets or several capsules.

Label-claim arithmetic on the anhydrous basis:

• 100 mg calcium per serving needs about 339 mg of dicalcium phosphate.
• 200 mg calcium per serving needs about 678 mg.
• 500 mg calcium per serving needs about 1,695 mg.

These figures exclude overage and assume the theoretical calcium content. Use the assay on the certificate of analysis for production, or the elemental content calculator. When dicalcium phosphate is used only as a filler, it still adds calcium and phosphorus to the product. Account for that in the declared nutrient content and against national maximum levels.

How dicalcium phosphate compares to other calcium forms

Calcium carbonate and tricalcium phosphate deliver more calcium per gram. Calcium citrate delivers less but differs in solubility and taste. Dicalcium phosphate sits between them and is the form most often chosen when the filler and mineral roles overlap. The calcium forms guide and the calcium carbonate vs calcium citrate comparison cover the wider choice.