A 54-year old female presented with fluctuating consciousness and seizures 4-weeks after gastric sleeve surgery. On admission blood glucose was 1.1 mmol/l, GCS was 10 and she was tachycardic. Examination was otherwise unremarkable. Her GCS improved after Glucagon and Glucogel. She described episodes of disorientation, slurred speech, fatigue and dysthesia since her surgery. These occurred particularly in the morning and her symptoms improved after eating. Her fluctuating consciousness continued necessitating intubation. Blood glucose levels were poorly documented at this time. Cerebral imaging and lumbar puncture were normal but an EEG showed non-convulsive status epilepticus. Administration of Levetiracetam led to resolution of seizure activity. Over the following days she had recurrent hypoglycaemia, particularly in the early morning, which had no temporal relation to meals. Her gastric sleeve diet was therefore abandoned. During one episode of hypoglycaemia (2.7 mmol/L), Insulin and C-peptide were found to be inappropriately raised (36.3 mU/L and 2.08 nmol/L respectively; reference ranges <13.0 mU/L and 0.36-1.12 nmol/L), raising the likely diagnosis of insulinoma. MRI of pancreas demonstrated a 16 mm pancreatic head mass, however an Octreotide scan was negative. Interestingly, review of a CT scan from 2007 showed that a small pancreatic lesion had been present then. At a surgical MDT, Whipples procedure, tumour enucleation and radiofrequency ablation were all considered but due to the patients BMI (39) these were felt to be either too high-risk or too technically challenging. Good glycaemic control was achieved with Diazoxide (200 milligrams BD). The plan is to reassess the patient for curative surgery if she can loose weight. This unusual case raises the possibility that the insulinoma had contributed to her weight gain. Its presence was only revealed following gastric sleeve surgery and commencement of the post surgery diet. We will discuss this in more depth and review the causes of hypoglycaemia post bariatric surgery.