summary
Vitamin D deficiency is very common in the elderly, and the geriatric patient is probably at even greater risk. Vitamin D plays an important role in calcium homeostasis; recent studies point to a possible causal link between vitamin D deficiency and the development and severity of depression. In this article we focus on an 80-year-old patient with depression and severe vitamin D deficiency and give advice on the diagnosis and treatment of vitamin D deficiency. To supplement the current multidisciplinary guidelines on depression, we recommend routine testing of serum vitamin D level prior to confirming the diagnosis of depression in the elderly.