MON-807 Vitamin D Deficiency Treatment with Long Term High-Dose Intermittent Dosing Appears Equally Safe and More Effective than Daily Dosing.

Abstract Disclosure: R.D. Paparodis: None. D. Bantouna: None. N.G. Angelopoulos: None. S. Livadas: None. J.C. Jaume: None. D.T. Papadimitriou: None. INTRODUCTION Vitamin D deficiency (VDD) (25(OH)D < 30ng/ml) is an extremely common endocrine condition, affecting bone health and predisposing to illness. Its correction (maintain D: 40-60 ng/ml) can follow several formats, often unsuccessful [Paparodis et al. Nutrients 2023. Dec 28;16(1):111]. Several studies suggest a lower dose daily dosing (LDDD) as the preferred strategy, as compared to high dose intermittent dosing (HDID), but safety and compliance - related efficacy outcomes are missing. We designed the present study to address this issue. Methods We performed a retrospective review of all the patients attending our Endocrine Clinics over 10 years, in regard to serum vitamin D concentrations, treatments used and duration and patient adherence, including adverse events, such as nephrolithiasis, hypercalcemia or high vitamin D (>100 ng/ml). The effects of the historically used LDDD were compared to HDID. Our clinics’ dosing regimen depended on baseline D as follows: D < 10 ng/ml: initial loading with 25.000 IU 3/week for 2 months, followed by 25.000 IU 1/week ever after. D 10-19.9 ng/ml: initial loading with 25.000 IU 2/week for 2 months, followed by 25.000 IU 1/week for 2 months and then 25.000 IU every 2 weeks thereafter. D 20-29.9 ng/ml: initial loading with 25.000 IU 1/week for 2 months, followed by 25.000 IU 1/2 weeks for 2 months and then 25.000 IU every month thereafter. Corrections compelled doubling the dose for 2 months when insufficient (D<30ng/ml) or halving the dose when overly sufficient (D>60ng/ml). Results Overall, we evaluated 12,188 patients and 2248 adhered to their treatment strategy >80%. Historical controls (CON) included 673 patients with current use of LDDD for 8-120 months, and 1575 patients on HDID intervention arm (INT) followed for 3.7±2.1 years. Adequacy was found in 319/673 CON (47.4%) after a mean 17.5±24.1 months of treatment with 1772±1994IU daily vs. 1482/1575 (94.1%) on INT arm after 2 months, 765/849 (89.0%) at 1 year, 554/621 (89.1%) at 2 years, 392/436 (89.9%) at 3 years, 254/287 (92.0%) at 4 years and 181/200 (90.5%) at 5 years (Overall adequacy n=3628/2968, 91.4%). Increased D was found in n=0 CON and n=3 INT subjects (129.2, 174.1, 100.9ng/ml), without clinical consequences. Hypercalcemia (>10.4mg/dl) was noted in n=3 CON and n=8 INT (p>0.05), (n=1 not related to hyperparathyroidism). Nephrolithiasis ensued in n=4 CON and n=5 INT (3/4 and 4/5 respectively with history of micro-or nephrolithiasis), p>0.05. Conclusions: HDID appears safe and more effective in treating VDD than LDDD regimens, probably due to better compliance. The proposed regimen attained a remarkably high and sustained success rate, without increased risk of complications, and should be evaluated further in prospective, randomized controlled trials. Presentation: Monday, July 14, 2025