<p>Hypocalcaemia is common in elderly patients and is usually attributed to vitamin D deficiency or inadequate calcium intake. Recurrent symptomatic hypocalcaemia despite long-term supplementation is uncommon and suggests an underlying metabolic abnormality. We report a 75-year-old woman with recurrent hypocalcaemic spasms over two years, with increased frequency over three months, requiring repeated intravenous calcium therapy. Despite prolonged oral calcium and vitamin D supplementation, she continued to develop symptoms. Biochemical evaluation revealed low-normal parathyroid hormone levels, normal renal function, and clinical response to magnesium during acute episodes. A diagnosis of functional hypoparathyroidism secondary to magnesium deficiency was considered. Treatment with calcium citrate, calcitriol, and oral magnesium resulted in sustained clinical improvement. This case highlights the importance of evaluating magnesium status in elderly patients with refractory hypocalcaemia.</p>