Background Vitamin D deficiency is an established risk factor for osteoporosis and fragility fractures in the elderly. However, its prevalence and association with specific anatomic fracture sites remain incompletely understood. This study aimed to assess vitamin D status and investigate its variation across fracture sites in elderly patients with fragility fractures. Methods A total of 2543 hospitalized patients aged ≥60 years with fragility fractures were included. Serum 25(OH)D concentrations were measured by liquid chromatography–tandem mass spectrometry. Demographic characteristics, admission indications, and comorbidities were extracted from electronic medical records to assess the prevalence of vitamin D deficiency and identify associated risk factors. A generalized linear model with a gamma distribution was used to analyze the association between serum 25(OH)D concentration and fracture site, adjusting for age, sex, sampling season, and comorbidities. Results Overall, 35.9% of patients were vitamin D deficient (20 ng/mL), 44.2% were insufficient (20–30 ng/mL), and 19.9% were sufficient. The median serum 25(OH)D concentration was 22.60 ng/mL (IQR: 17.30–28.30). Multivariable analysis showed that age (OR 1.036 per year), female sex (OR 1.358), winter season (OR 2.040), and a history of cerebral infarction (OR 1.660) were independently associated with vitamin D deficiency (all p 0.05). Serum 25(OH)D concentrations differed significantly across fracture sites ( p 0.05): hip fractures (22.20 ng/mL) and multiple fractures (20.95 ng/mL) had the lowest levels, while vertebral fractures (25.40 ng/mL) had the highest. Conclusion Vitamin D deficiency is highly prevalent in older adults with fragility fractures and is significantly associated with advancing age, female sex, winter season, and a history of cerebral infarction. After multivariable adjustment, serum 25(OH)D concentrations differed significantly across fracture sites. This difference may reflect the dual role of vitamin D in neuromuscular function and bone metabolism, underscoring the need for longitudinal interventional studies to further explore these relationships.
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