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A major randomized trial found that high-dose vitamin D3 supplementation didn't reduce deaths in dialysis patients. The SIMPLIFIED trial — one of the largest dialysis trials ever — followed nearly 3,900 patients for up to 7.5 years and found no significant difference in all-cause mortality. Researchers say the findings don't support routine population-wide supplementation with high-dose cholecalciferol in this group.
Despite vitamin D deficiency being extremely common — and linked to higher mortality — among patients on kidney dialysis, a large randomized trial found that correcting it with high-dose supplementation doesn't actually improve survival. The SIMPLIFIED trial enrolled 3,866 dialysis patients across 55 UK centers, randomizing them to receive oral cholecalciferol (60,000 IU every two weeks) or standard care for up to 7.5 years.
The results were clear: no significant reduction in all-cause mortality (45.5% vs. 48.5%), and no meaningful improvements in cardiovascular hospitalizations, infections, or fractures. A modest reduction in a composite cardiovascular events score (MACE) was observed, but researchers cautioned it was largely driven by revascularization procedures and the trial wasn't powered for that outcome.
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Why it matters: Current KDIGO guidelines recommend correcting vitamin D deficiency in dialysis patients, but this trial challenges the assumption that doing so translates to better outcomes. Researchers are calling on KDIGO to factor these findings into future guideline updates.
