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Vitamin D Supplement (Native Vitamin D3)

Colecalciferol 1000–2000 units/day

Brand names: InVita D3, Fultium-D3, Thorens (high-dose)

Adult dose

Dose: CKD stage 3–4: 1000–2000 units (25–50 micrograms) once daily. Vitamin D deficiency loading: 40,000–60,000 units weekly for 6–8 weeks, then maintenance 1000–2000 units/day.
Route: Oral
Frequency: Once daily (maintenance); once weekly (loading)
Max: 4000 units/day maintenance; loading doses up to 300,000 units as single bolus under specialist guidance
For 25-OH vitamin D insufficiency/deficiency in CKD stages 3–4. Unlike calcitriol/alfacalcidol (active forms), colecalciferol requires 1-alpha hydroxylation in the kidney — residual renal function is needed. In CKD stage 5/dialysis, use active vitamin D analogue (calcitriol or alfacalcidol) instead.

Paediatric dose

Route: Oral
Frequency: Once daily
Max: Age-based: infants 400 units/day; children 1–6 years: 600 units/day; children >6 years: 1000–2000 units/day
Concentration: 400 units/mL drops; 1000 units, 3000 units, 20,000 units capsules units/day/ml
Paediatric CKD: 1000–2000 units OD for CKD stage 3–4. Use active vitamin D analogues (alfacalcidol) in advanced CKD/dialysis. Specialist paediatric nephrology.

Dose adjustments

Renal

CKD stage 1–4: use colecalciferol (requires residual renal 1-alpha hydroxylase activity). CKD stage 5/dialysis: must use active vitamin D analogues (calcitriol or alfacalcidol) as 1-alpha hydroxylation is severely impaired.

Hepatic

Caution in severe hepatic impairment — 25-hydroxylation occurs in liver; impaired in severe disease; monitor 25-OH vitamin D levels

Clinical pearls

  • KDIGO CKD-MBD 2017: measure 25-OH vitamin D in all CKD patients; supplement if <50 nmol/L (deficient) or 50–75 nmol/L (insufficient) — same treatment thresholds as general population
  • Key distinction: colecalciferol (native D3) is appropriate for CKD stages 1–4 where residual renal function allows 1-alpha hydroxylation; in stage 5/dialysis, the kidney cannot activate D3 — use calcitriol or alfacalcidol instead
  • Vitamin D deficiency is near-universal in dialysis patients (90%+) and contributes to secondary hyperparathyroidism, bone disease, fatigue, and muscle weakness
  • Loading vs maintenance: rapid correction of severe deficiency (<25 nmol/L) requires loading doses (40,000 units/week × 6–8 weeks) before switching to daily maintenance
  • Do not use colecalciferol as a substitute for calcitriol/alfacalcidol in CKD stage 5 — native vitamin D cannot be adequately activated and will not suppress PTH effectively

Contraindications

  • Hypercalcaemia
  • Hypervitaminosis D
  • Nephrolithiasis with hypercalciuria
  • Sarcoidosis or granulomatous disease (increased sensitivity to vitamin D — risk of hypercalcaemia)

Side effects

  • Hypercalcaemia (excess dosing — nausea, confusion, polyuria, constipation)
  • Hypercalciuria
  • Nephrolithiasis (long-term excess)
  • Headache (hypercalcaemia)

Interactions

  • Thiazide diuretics — increased calcium reabsorption → hypercalcaemia risk
  • Digoxin — hypercalcaemia increases digoxin toxicity
  • Cholestyramine/colestipol — reduce vitamin D absorption (fat-soluble vitamin)
  • Calcium-based phosphate binders — additive hypercalcaemia risk with high vitamin D doses

Monitoring

  • 25-OH vitamin D levels (at baseline; at 3 months after loading; annually when stable)
  • Serum calcium (within 4 weeks of starting or dose increase)
  • Serum phosphate
  • PTH (every 3–6 months in CKD stage 3–5)

Reference: BNFc; BNF; KDIGO CKD-MBD Guidelines 2017; NICE NG203; NICE CG71 (Vitamin D deficiency). Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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