A 3-year-old is lethargic and has been drinking more fluids than normal for weeks. Conjunctivae are dry. Vital signs show tachycardia. What should you suspect?

• A. Organophosphate exposure
• B. Carbon monoxide exposure
• C. Anaphylactic shock
• D. Hyperglycemia

Answer: (D)

Osmotic diuresis from hyperglycemia is the key idea. When blood glucose rises, the kidneys can’t reabsorb all the glucose, so water follows into the urine, producing increased urination and thirst. The result in a small child is dehydration, which shows up as dry conjunctivae and a rapid pulse, and the lethargy can follow from reduced circulating volume and metabolic stress. This pattern is most consistent with hyperglycemia, likely from new-onset type 1 diabetes mellitus, and it may progress to diabetic ketoacidosis if not addressed.

Organophosphate exposure would present with cholinergic signs (excess secretions, bradycardia, bronchorrhea). Carbon monoxide exposure typically causes headache, confusion, and hypoxia-related symptoms rather than a polyuria/polydipsia dehydration picture. Anaphylactic shock features airway swelling, hypotension, and urticaria or wheezing. The patient’s combination of polyuria/polydipsia, dehydration, and tachycardia points to hyperglycemia as the best explanation.