Society of Diabetic Nephropathy Prevention Journal of Nephropharmacology 2345-4202 15 2 2026 07 01 Vitamin D supplementation in chronic kidney disease; effects on proteinuria, disease progression, and cardiovascular outcomes e12882 e12882 10.34172/npj.12882 EN Farzaneh Futuhi https://orcid.org/0000-0001-7137-2408 Zahra Sahraei https://orcid.org/0000-0002-0178-8624 Behzad Azimi https://orcid.org/0000-0002-4909-6969 Journal Article 10.34172/npj.12882 2026 04 12 2026 06 08 Chronic kidney disease (CKD) is commonly accompanied by vitamin D deficiency, largely due to impaired renal conversion of 25-hydroxyvitamin D [25(OH)D] to its biologically active form, 1,25-dihydroxyvitamin D [1,25(OH)₂D]. In addition to its classical role in calcium–phosphate homeostasis and bone metabolism, vitamin D exerts multiple extra-skeletal effects, including modulation of renal function, cardiovascular health, and endocrine pathways, primarily through activation of the vitamin D receptor (VDR) and suppression of the renin–angiotensin–aldosterone system (RAAS). This narrative review synthesizes current evidence on the impact of vitamin D supplementation encompassing nutritional forms (cholecalciferol and ergocalciferol) and active or analog forms (calcitriol, paricalcitol, and calcifediol) on proteinuria, CKD progression, and cardiovascular outcomes. A targeted literature search was conducted across PubMed, Web of Science, Scopus, DOAJ, and Google Scholar. Evidence from multiple randomized trials and meta-analyses indicates that active vitamin D analogues, particularly paricalcitol, are associated with consistent reductions in proteinuria among patients with CKD. Nutritional vitamin D, especially cholecalciferol, has also demonstrated potential antiproteinuric effects in selected populations. Observational data consistently show that vitamin D deficiency is independently associated with accelerated decline in estimated glomerular filtration rate (eGFR) and increased risk of progression to end-stage renal disease (ESRD); however, interventional studies have not conclusively demonstrated that vitamin D supplementation slows CKD progression. Similarly, while observational studies link low vitamin D levels with increased cardiovascular morbidity and higher mortality, randomized trials have not consistently shown significant improvements in major cardiovascular outcomes. Overall, vitamin D supplementation, particularly active analogues, appears beneficial for proteinuria reduction. Still, its effects on renal disease progression and cardiovascular endpoints remain uncertain, underscoring the need for larger clinical trial studies.