Vitamin D analogue (cholecalciferol) Pregnancy: Considered safe and recommended at standard doses. NICE recommends 10 mcg (400 IU) daily for all pregnant and breastfeeding women.

Colecalciferol (Vitamin D3)

Brand names: Fultium-D3, Desunin, Invita D3, Stexerol-D3, Aviticol, Pro D3

Adult dose

Dose: Maintenance / preventive: 800–2000 IU OD (NOS 2018 guidelines). Loading regimens for proven deficiency (25-OH vit D <25 nmol/L): 50,000 IU once weekly for 6 weeks (total 300,000 IU); or 20,000 IU twice weekly for 7 weeks; or 4000 IU OD for 10 weeks. Then maintenance 800–2000 IU OD.

Route: Oral

Frequency: Once daily (maintenance) or once weekly (loading)

Max: 10,000 IU/day chronic; loading regimens up to 50,000 IU/week

Take with main fatty meal for absorption. Many UK products are fungal-derived — confirm vegetarian/vegan acceptability with patient.

Paediatric dose

Route: Oral

Frequency: Once daily

Universal supplementation (NICE PH56): birth–4 yrs 400 IU OD; >4 yrs and adults at risk 400–800 IU OD. Treatment of rickets/deficiency: <6 months 3000 IU OD for 8–12 weeks; 6 mo–12 yrs 6000 IU OD for 8–12 weeks; >12 yrs adult dose. BNFc.

Dose adjustments

Renal

Use alfacalcidol or calcitriol if eGFR <30 — colecalciferol requires renal 1α-hydroxylation.

Hepatic

Caution; severe hepatic impairment may impair 25-hydroxylation.

Clinical pearls

Universal recommendation in UK (NICE PH56, RCPCH, NHS): 400 IU/day for ALL infants and toddlers, and 400 IU/day for adults at risk (limited sun exposure, dark skin, elderly, pregnant, breastfeeding) — OTC pharmacy supply.
Diagnosis: 25-hydroxyvitamin D level (NOT 1,25). Deficiency <25 nmol/L; insufficiency 25–50; sufficient ≥50. Recheck 3 months after loading — measuring earlier is unreliable.
ALWAYS check calcium and renal function before high-dose loading — granulomatous disease (sarcoidosis, TB, lymphoma) can cause life-threatening hypercalcaemia with vitamin D supplementation.
Vegan/halal: most UK preparations are sheep-wool lanolin derived; D3 from lichen is available (e.g., Vitabiotics) for vegans.
Combination with calcium (Adcal-D3, Accrete D3) for osteoporosis prevention/management — note increased CV risk signal with HIGH calcium intake (>1500 mg/day).
After bariatric surgery: high-dose colecalciferol commonly required (3000–6000 IU/day); annual monitoring.

Contraindications

Hypercalcaemia or vitamin D toxicity
Metastatic calcification
Renal calculi (active)
Sarcoidosis or other granulomatous disease (relative — extra-renal 1α-hydroxylation can cause hypercalcaemia)
Williams syndrome

Side effects

Hypercalcaemia (rare at typical doses; risk with very high cumulative doses or granulomatous disease)
Hypercalciuria, nephrocalcinosis (with chronic high dose)
Constipation, GI upset
Headache
Pruritus, rash (rare)

Interactions

Thiazide diuretics: additive ↑ Ca — caution combining at high doses
CYP3A4 inducers (phenytoin, carbamazepine, phenobarbital, rifampicin): ↑ vitamin D metabolism — consider higher dose
Orlistat: ↓ absorption — separate by ≥2 hours
Cholestyramine, colestipol: ↓ absorption
Glucocorticoids (long-term): antagonise vitamin D effects on calcium absorption
Digoxin: hypercalcaemia ↑ digoxin toxicity

Monitoring

25-OH vitamin D 3 months after loading then annually if deficient
Adjusted calcium at baseline; recheck if symptoms or high-dose loading
Renal function in elderly/CKD

Reference: BNFc; BNF 90; BNF for Children 2024; NICE PH56 (Vitamin D 2014, updated 2017); NOS Vitamin D & Bone Health 2018; RCPCH Vitamin D Guidance. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Pathways