Objectives: To determine the prevalence of vitamin D deficiency and hyperparathyroidism in older patients with low trauma fractures, and to develop a statistical model to predict the serum level of 25‐hydroxyvitamin D required to prevent secondary hyperparathyroidism. Method: Descriptive cohort study conducted in an aged care centre in Melbourne, Australia. Participants comprised 107 patients aged over 65 years with low trauma fractures. Serum 25‐hydroxyvitamin D (25OHD), parathyroid hormone (PTH) and plasma creatinine levels were measured. Anthropometric data, Barthel index, Mini‐Mental State Examination and use of diuretics were also assessed. Results: Fifty‐one per cent of patients had 25OHD <30 nmol/L and 86% had 25OHD <50 nmol/L. Thirty‐two per cent had secondary hyperparathyroidism which was significantly associated with vitamin D deficiency and use of frusemide. Statistical models demonstrated higher PTH at serum 25OHD below 60 nmol/L. Conclusions: Vitamin D deficiency is common among older people. Serum 25OHD may need to be greater than 60 nmol/L to prevent secondary hyperparathyroidism.