SAT-547 Doxycycline induced hypoglycemia within 24 hours

Abstract Disclosure: F. Abdulle: None. H. Dave: None. A. Abushamma: None. A. Diwakar: None. Hypoglycemia is defined as blood glucose BG levels below 60 mg/dL and is considered a serious medical emergency. It requires immediate treatment, as untreated, it may lead to neurological deficits. While hypoglycemia in non-diabetic patients is rare, certain medications contribute. Doxycycline, a broad-spectrum tetracycline, commonly prescribed for pneumonia. We present a case of a non-diabetic male who developed hypoglycemia following treatment with oral doxycycline for suspected community-acquired pneumonia. A 66-year-old male with a past medical history of diastolic heart failure and obstructive sleep apnea presented with dyspnea. He was admitted to the inpatient hospital floor for acute hypoxic respiratory failure, likely in the setting of heart failure. CT revealed mild infiltrates, and IV ceftriaxone and oral doxycycline 100 mg were initiated. After the second dose of doxycycline, the patient became acutely diaphoretic, with a BG reading of 20 mg/dL and a (POC) point-of-care glucose of 40 mg/dL. Vitals were stable. Doxycycline was discontinued, he was managed with a D10 drip and transferred to the intensive care unit. Management continued with a D10 boluses, and POC checks hourly; ranging between 48-136 mg/dL. Endocrinology were consulted. Possible causes of hypoglycemia, including insulin autoimmune hypoglycemia, insulinoma, sulfonylureas, hypothyroidism, and adrenal insufficiency, were ruled out. The latter was confirmed with a negative cosyntropin stimulation test, showing an appropriate cortisol response (basal 11.7 µg/dL, 30 minutes 21.7 µg/dL, 60 minutes). C-peptide levels were found to be 0.8 ng/mL and insulin antibodies were negative. The patient was transferred to a regular nursing floor and discharged without further hypoglycemic events. Hypoglycemia in non-diabetic patients is a rare occurrence. Drug-induced hypoglycemia is the most common etiology. Limited case reports have described doxycycline-induced hypoglycemia in non-diabetics. Further, these document hypoglycemic events after six days of doxycycline use. The elimination half-life of doxycycline is estimated between 15 and 20 hours. Our patient received the first dose on 11/14/2024 at 15:30 and second dose on 11/15/2024 at 06:30. He developed hypoglycemia two hours after the second dose, with symptoms resolving by 12:20. This timeline suggests that the first dose of doxycycline was likely the cause. Our case is the first reported doxycycline-induced hypoglycemia occurring within 24 hours, which is consistent with the drug’s half-life. The mechanism by which doxycycline causes hypoglycemia remains unclear, but theories suggest it may increase insulin sensitivity or prolong insulin half-life by inhibiting its degradation in the liver. Given that doxycycline is commonly prescribed in outpatient settings, it is vital for clinicians to be aware of this rare but potentially serious side effect. Presentation: Saturday, July 12, 2025