Prolonged Clinical Remission of Type 1 Diabetes Sustained by Calcifediol and Low-Dose Basal Insulin: A Case Report

herein, we describe an unusually prolonged duration (31 months) of the clinical remission phase in a 22-year-old Italian man with new-onset type 1 diabetes. shortly after the disease diagnosis, the patient was treated with calcifediol (also known as 25-hydroxyvitamin D3 or calcidiol), coupled with low-dose basal insulin, to correct hypovitaminosis D and to exploit the anti-inflammatory and immunomodulatory properties of vitamin D. during the follow-up period, the patient retained a substantial residual beta-cell function and remained within the clinical remission phase, as evidenced by an insulin dose-adjusted glycated hemoglobin value <9. At 24 months, we detected a peculiar immunoregulatory profile of peripheral blood cells, which may explain the prolonged duration of the clinical remission sustained by calcifediol as add-on treatment to insulin.Plain language summary: we describe the case of a 22-year-old Italian man who was treated with a form of vitamin D called calcifediol shortly after the diagnosis of type 1 diabetes, which is an autoimmune condition leading to insulin deficiency and to the lifelong need for insulin therapy. calcifediol was administered, coupled with low-dose insulin, to correct vitamin D insufficiency and to exploit the anti-inflammatory properties of vitamin D. during the follow-up period (31 months), the patient unexpectedly remained on once-daily insulin injection therapy and maintained near-normal blood glucose levels. these findings suggest that calcifediol administration may represent a valid add-on treatment to insulin, with the aim of reducing daily insulin requirements and improving glucose control in patients with recent-onset type 1 diabetes.