Calcium Supplement Pregnancy: During pregnancy and lactation treatment should be under the direction of a physician. Requirements for calcium are increased in pregnancy and lactation, but in deciding on the required supplementation allowance should be made for availability of these agents from other sources. If calcium and iron supplements are both required they should be taken at different times.

Calcium Carbonate

Brand names: Calcichew, Adcal, Calcichew D3 (with colecalciferol)

Used in: Osteoporosis

Calcium carbonate is a calcium salt used as a calcium supplement, in osteoporosis prophylaxis (often with vitamin D) and as a phosphate binder in chronic kidney disease.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Dietary deficiency and as an adjunct in osteoporosis therapy: 2 chewable tablets per day (fetched SPC product: Adcal 1500 mg chewable tablets)

Route: Oral — the tablets should be chewed, not swallowed whole, and taken just prior to, during or immediately following a meal

Frequency: Preferably one tablet each morning and evening

The SPC gives this regimen for 'Adults, elderly and children' as a single statement and provides no separate paediatric or per-kg dose. PHOSPHATE BINDING: for use in binding phosphate in the management of renal failure in patients on renal dialysis, the dose should be adjusted for the individual patient and is dependent on the serum phosphate level — no fixed dose is stated in the source. The elemental calcium content per tablet is not stated in the fetched sections; the clinician should confirm the elemental calcium equivalent from the full SPC before converting between products, since calcium products are commonly prescribed by elemental calcium content. Allowances should be made for calcium and vitamin D supplements from other sources. With long-term treatment it is advisable to monitor serum and urinary calcium levels and kidney function, and to reduce or stop treatment temporarily if urinary calcium exceeds 7.5 mmol/24 hours. Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrase-isomaltase insufficiency should not take this medicine. FOR CROSS-REFERENCE ONLY (different product and indication): a US over-the-counter antacid label containing calcium carbonate (Advance Pharmaceutical, 2017) directs 'take one to four tablets daily, do not take more than 4 tablets in 24 hours, do not use the maximum dosage for more than 2 weeks' — that is antacid dosing, not calcium supplementation, and the tablet strength is not stated.

Dose adjustments

Renal

Severe renal failure untreated by renal dialysis is an absolute contraindication. Patients with mild to moderate renal failure (or mild hypercalciuria) should be supervised carefully with periodic checks of plasma calcium levels and urinary calcium excretion. In patients with a history of renal stones, urinary calcium excretion should be measured to exclude hypercalciuria.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Absolute: hypercalcaemia resulting for example from myeloma, bone metastases or other malignant bone disease, sarcoidosis, primary hyperparathyroidism and vitamin D overdosage
Absolute: severe renal failure untreated by renal dialysis
Absolute: hypersensitivity to any of the tablet ingredients
Relative: osteoporosis due to prolonged immobilisation, renal stones, severe hypercalciuria

Side effects

Constipation (rare)
Flatulence (rare)
Nausea (rare)
Gastric pain (rare)
Diarrhoea (rare)

Interactions

Thiazide diuretics — risk of hypercalcaemia should be considered since these drugs reduce urinary calcium excretion
Digitalis and other cardiac glycosides — hypercalcaemia must be avoided in digitalised patients; effects may be accentuated by oral calcium combined with vitamin D. Strict medical supervision and, if necessary, ECG and calcium monitoring are needed
Thyroxine, bisphosphonates, sodium fluoride, quinolone and tetracycline antibiotics, and iron — calcium salts may reduce their absorption; allow a minimum period of four hours before taking the calcium
Certain foods (e.g. those containing oxalic acid, phosphate or phytinic acid) may reduce the absorption of calcium
Systemic corticosteroid therapy reduces calcium absorption — take into account with concomitant therapy

Clinical monograph

How it works

It provides elemental calcium to support bone mineralisation and, in the gut, binds dietary phosphate to reduce its absorption in renal disease.

Prescribing in practice

Avoid in hypercalcaemia and severe hypercalciuria, and use with caution where there is a risk of milk-alkali syndrome or renal stones.
It reduces the absorption of several drugs, including some antibiotics, levothyroxine and bisphosphonates, so doses should be separated.
As a phosphate binder it is taken with food, whereas as a supplement absorption is best with food and adequate vitamin D.

Monitoring

Monitor serum calcium (and phosphate when used as a binder) particularly in renal impairment.

Counselling the patient

Separate this medicine in time from thyroid medication, certain antibiotics and bisphosphonates.
Take with food when used to lower phosphate.
Report symptoms such as nausea, constipation or confusion that could suggest high calcium.

Evidence & guidelines

Calcium with vitamin D supplementation is recommended by NICE within osteoporosis management for at-risk patients.

Reference: NICE CG146 (Osteoporosis); NICE CG182 (CKD); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Calcium lactate · Calcium supplement

Pathways