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Vitamin D2

Ergocalciferol

Brand names: various

Ergocalciferol (vitamin D2) is a vitamin D preparation used to prevent and treat vitamin D deficiency and associated conditions such as rickets and osteomalacia.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It is hydroxylated in the liver and kidney to active calcitriol, which promotes intestinal absorption of calcium and phosphate and supports bone mineralisation.

Prescribing in practice

  • Avoid in hypercalcaemia and use with caution where there is a risk of hypercalcaemia (for example sarcoidosis or renal impairment), as excessive intake causes vitamin D toxicity with hypercalcaemia.
  • Ensure adequate calcium intake when correcting deficiency and confirm the diagnosis before prolonged high-strength treatment.
  • Take account of total vitamin D from all supplements and combination products to avoid inadvertent overdose.

Monitoring

Monitor serum calcium (and renal function where relevant) during higher-dose treatment, particularly in patients predisposed to hypercalcaemia.

Counselling the patient

  • Do not take additional vitamin D supplements without advice, as too much can be harmful.
  • Report symptoms of high calcium such as nausea, excessive thirst, constipation or confusion.

Evidence & guidelines

Vitamin D supplementation to prevent and treat deficiency is supported by NICE guidance and UK public health recommendations.

Reference: NICE NG121; Royal Osteoporosis Society; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

Pathways