Calcium phosphate

How it works

It provides elemental calcium (with phosphate) for absorption, supporting serum calcium, bone mineralisation and neuromuscular function.

Prescribing in practice

• Avoid in hypercalcaemia, hypercalciuria and conditions with raised serum phosphate, including significant renal impairment, where the additional phosphate load can be harmful.
• Separate from oral tetracyclines, quinolones, levothyroxine, iron and bisphosphonates, whose absorption is reduced by calcium.
• Because it contains phosphate, it is generally less suitable than other calcium salts where phosphate restriction is required.

Monitoring

Monitor serum calcium, phosphate and renal function periodically, especially with long-term use or impaired renal function.

Counselling the patient

• Take as directed, generally with food.
• Leave a gap between this and antibiotics or thyroid tablets.
• Report symptoms of high calcium such as nausea, constipation, thirst or confusion.

Evidence & guidelines

Calcium salts are well established for correcting calcium deficiency; the choice of salt is guided by phosphate status and tolerability.