An 86-year old man was admitted to hospital with gradual decline in mobility and leg weakness. Co-morbidities included atrial fibrillation, hypertension and osteoarthritis. The adjusted serum calcium on admission was 3.42 mmol/l; bone profile showed phosphate 0.56 mmol/l, alkaline phosphatase 140 U/l, albumin 34 g/l, parathyroid hormone 21.4 pmol/l. He was vitamin-D replete (68 nmol/l) with normal renal function. The hypercalcaemia was not thought to be due to any medications. Urgent treatment was commenced with 45 mg disodium pamidronate intravenously and 4 hourly intravenous fluid replacement. Further investigations included a negative myeloma screen, normal serum ACE, unremarkable plain film chest X-ray, 24-hour urine calcium output 2.5 mmol/24 h (2.57.5 mmol/24 h). Parathyroid ultrasound scan identified a nodule posterior to the right thyroid lobe measuring 1.4×1×2.7 cm with a concordant focus of delayed washout on nuclear medicine parathyroid uptake scan. Pamidronate therapy led to a reduction of calcium to 2.98 mmol/l over 4 days, but the effect was short lasting, necessitating a second dose of intravenous pamidronate. However, the calcium again increased to 3.14 mmol/l within 4 days and Cinacalcet 30 mg daily was commenced. Due to persistent hypercalcaemia requiring continuous intravenous fluid replacement and not responding to medical therapy, an urgent surgical referral was made to the Surgical Endocrine unit at our linked tertiary centre. He was transferred to the tertiary unit and had a parathyroidectomy which revealed a large adenoma of the right superior gland. The left side was not explored due to convincing findings on the right and a sufficient drop in intraoperative PTH (204 mmol/l). He was transferred back to our hospital for further rehabilitation and recovered well, being discharged shortly thereafter. Adjusted calcium levels remained <2.6 mmol/l, PTH 3.8 mmol/l and no further intravenous fluids, bisphosphonate or calcimimetics were required. This uncommonly encountered case highlights non-malignant hypercalcaemia resistant to medical therapy and successful non-elective inpatient parathyroidectomy as part of the armamentarium for treatment of patients, even the very elderly, who are either symptomatic or requiring continuous intravenous fluid replacement. This is in contrast to the majority of patients with hypercalcaemia, managed in an outpatient setting, where there are clear guidelines indicating surgical management. Early parathyroid adenoma localisation studies and discussion with the Endocrine Surgical team should be considered if concerns are raised over resistant hypercalcaemia secondary to primary hyperparathyroidism, to facilitate definitive treatment and optimise outcomes.