Vitamin D2 Pregnancy: Should not be used in pregnancy unless the potential benefit outweighs the potential hazards to the fetus (limited data; animal studies show fetal abnormalities with hypervitaminosis D). Should not be administered to breast-feeding mothers (excreted in milk; can cause infant hypercalcaemia - monitor infant serum calcium if used). US label: Pregnancy Category C.

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.

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: 300,000 IU as a single dose

Route: Intramuscular injection

Frequency: Every 3-6 months

Adults and elderly: this eMC product (Ergocalciferol 300,000 IU Solution for Injection) is typically administered as a single IM dose of 300,000 IU every 3-6 months. Paediatric (children 1-12 years): a bolus dose of 300,000 IU is generally given in 2 divided doses (not a per-kg dose). For all age groups the dose should be individualised by the clinician per clinical response and requirements. Monitor serum and urinary calcium, phosphate and BUN at regular intervals (initially weekly) to achieve optimum response and avoid hypercalcaemia; give calcium and phosphorus supplements where necessary. The range between toxic and therapeutic dosage is narrow.

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

Hypersensitivity to the active substance or any excipient
Hypercalcaemia
Evidence of vitamin D toxicity / hypervitaminosis D
Decreased renal function
Metastatic calcification

Side effects

Hypercalcaemia (very common)
Elevated serum creatinine (very common)
Hypercholesterolaemia, muscle weakness, muscle pain
Nausea, vomiting, anorexia, constipation
Polyuria, nephrocalcinosis, cardiac arrhythmias (associated with hypercalcaemia)

Interactions

Magnesium-containing antacids: hypermagnesaemia may develop in patients on chronic renal dialysis
Digitalis glycosides: hypercalcaemia in patients on digitalis may precipitate cardiac arrhythmias
Verapamil: atrial fibrillation may recur when supplemental calcium and ergocalciferol induce hypercalcaemia
Anticonvulsants (e.g. carbamazepine, phenobarbital, phenytoin, primidone): vitamin D requirements may be increased
Thiazide diuretics: hypoparathyroid patients may develop hypercalcaemia

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. 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.

Pathways