Vitamin D in Dialysis Patients
Dialysis patients (CKD stage 5) have essentially zero renal 1α-hydroxylase activity. Cholecalciferol supplementation raises 25(OH)D but doesn't convert to active calcitriol. Managing CKD-MBD in dialysis requires active vitamin D analogues, calcimimetics, and calcium/phosphate balance under nephrology supervision.
The active analogues
- Calcitriol (Rocaltrol) — the natural active hormone 1,25(OH)₂D. Effective for PTH suppression; risk of hypercalcaemia and vascular calcification.
- Paricalcitol (Zemplar) — synthetic analogue; PTH suppression with less calcium/phosphate rise than calcitriol. Widely used.
- Doxercalciferol (Hectorol) — 1α-hydroxyvitamin D₂; activated in liver rather than kidney; commonly used in dialysis.
- Calcifediol (Rayaldee) — extended-release 25(OH)D₃; used earlier in CKD to boost 25(OH)D and secondary PTH.
Cholecalciferol still has a role
Dialysis patients often have very low 25(OH)D even with active analogue therapy. Standard cholecalciferol (1,000-2,000 IU/day or 50,000 IU/week) to raise 25(OH)D above 30 ng/mL is standard alongside active analogues. Supports non-renal functions of vitamin D (immune, muscle, bone matrix quality).
Calcimimetics
Cinacalcet (Sensipar) and etelcalcetide (Parsabiv) sensitise the parathyroid calcium-sensing receptor, suppressing PTH without raising serum calcium. Often combined with lower doses of active vitamin D to control PTH while minimising vascular calcification.
KDIGO targets in dialysis
- Serum calcium: within normal range (avoid hypercalcaemia).
- Serum phosphate: toward normal.
- PTH: 2-9× upper limit of normal (roughly 130-585 pg/mL depending on assay).
- Avoid over-suppression of PTH (< 2× ULN) — adynamic bone disease.
What dialysis patients should NOT do
- Do not self-adjust vitamin D analogue doses.
- Do not stop calcimimetics without nephrology input.
- Do not use calcium-based supplements (e.g., Tums) as antacid without discussing with your kidney team — chronic accumulation contributes to vascular calcification.
- Do not take OTC magnesium without checking — dialysis alters magnesium handling.
- Sun exposure limits do not apply — even significant sun does not raise calcitriol without renal 1α-hydroxylase.