An 18-year-old woman with a history of hollow visceral myopathy presented with a small-bowel obstruction. High-dose opioid analgesia was required subsequently during hospital admission. She suffered two episodes of documented fasting hypoglycaemia, despite adjustment of parenteral carbohydrate administration. Investigations for non-insulin-mediated hypoglycaemia revealed a low morning cortisol of 109 nmol/L and an inappropriately low Adrenocorticotropic hormone (ACTH) level of 2.2 pmol/L. A diagnosis of secondary adrenal insufficiency was confirmed on repeat cortisol and ACTH testing. The 250 µg short Synacthen test cortisol response was normal, suggestive of acute rather than chronic ACTH deficiency. This pattern was consistent after further opioid exposure. Adrenal recovery occurred shortly after opioid cessation. Opioid-induced hypoadrenalism is likely an under-recognised clinical entity with potentially serious adverse patient outcomes. There are reported cases involving commonly prescribed opioids including fentanyl and tramadol. However, we believe this is the first reported clinical case of acute transient opioid-induced secondary hypoadrenalism associated with fasting hypoglycaemia.