Situation: A 70-year-old man with type 2 diabetes, chronic kidney disease (estimated glomerular filtration rate 28 mL/min/1.73 m²), and atrial fibrillation is admitted to the adult medical ward with an infected foot ulcer. On admission, his international normalized ratio (INR) is 2.6 and his capillary blood glucose is 286 mg/dL (15.9 mmol/L). On the third day, after the infusion has been stopped, the nurse realizes that at 11:30 the client received 10 units of subcutaneous regular insulin instead of the ordered 4 units. At 12:10 he is alert, sweaty, and able to swallow, and his capillary blood glucose is 58 mg/dL (3.2 mmol/L). His lunch tray has not yet arrived. What should the nurse do FIRST?

After a medication error, the nurse first assesses and monitors the client: regular insulin given 40 minutes ago has begun to act and peaks in 2 to 4 hours, so the extra 6 units can cause hypoglycemia over the next several hours. A glucose of 58 mg/dL (3.2 mmol/L) is hypoglycemia (below 70 mg/dL, 3.9 mmol/L), and because he is alert and able to swallow, the rule of 15 applies: 15 g of fast-acting carbohydrate, recheck in 15 minutes, then a meal. The physician is notified right after treatment, and the incident report follows.

Clinical context A medication error involving subcutaneous regular insulin has produced symptomatic hypoglycemia. The immediate priority is not documentation or notification, but rapid correction of the low glucose in a patient who can safely take oral carbohydrate.

Why the glucose is low Regular insulin given subcutaneously begins to act within 30 to 60 minutes and peaks at 2 to 4 hours. The client received 10 units instead of 4 units, an excess of 6 units. At 40 minutes after injection, the insulin is already lowering glucose, and the effect will continue to intensify over the next several hours. A capillary glucose of 58 mg/dL (3.2 mmol/L) is below the hypoglycemia threshold of 70 mg/dL (3.9 mmol/L), and the client is symptomatic with diaphoresis.

Why oral carbohydrate is correct The client is alert and able to swallow, which makes the oral route safe and appropriate. The rule of 15 is the standard first intervention for nonsevere hypoglycemia in an awake, cooperative patient: give 15 g of fast-acting carbohydrate, recheck glucose in 15 minutes, and repeat if the level remains below 70 mg/dL. The narrative review by Urbanová and colleagues confirms that 15 g of rapid-acting carbohydrate, preferably glucose, remains the recommended initial dose for nonsevere hypoglycemia in insulin-treated adults, with repeat dosing after 15 minutes if hypoglycemia persists ^[1]. This recommendation has remained stable despite advances in insulin delivery and glucose monitoring ^[1].

Why the other options are not first Watch out! Intravenous 50% dextrose is reserved for severe hypoglycemia when the patient cannot swallow, is unconscious, or has altered mental status. This client is alert and able to swallow, so oral carbohydrate is safer and avoids an unnecessary IV intervention. Serving lunch alone is insufficient because the meal has not arrived and the glucose is already low; a measured fast-acting carbohydrate dose provides predictable, rapid correction. Notifying the physician is important after a medication error, but treatment of hypoglycemia takes priority over notification and incident reporting. The physician should be informed promptly after the immediate glucose correction is initiated.

Monitoring after treatment Because the excess regular insulin will continue to act for several hours, a single correction is not the end of care. Key point! Recheck capillary glucose 15 minutes after the oral carbohydrate, and then follow with a meal or snack containing complex carbohydrate and protein to prevent recurrence. Continued monitoring is essential because the insulin peak has not yet been reached.

Medication error response sequence

Priority order	Action	Rationale
1	Assess and treat hypoglycemia	Glucose 58 mg/dL with symptoms requires immediate correction
2	Recheck glucose in 15 minutes	Confirms response and guides repeat dosing [1]
3	Notify physician	Reports the error and the client's status after initial treatment
4	Complete incident report	Documents the error and interventions for quality review

Clinical pearl The case report by Kim and colleagues illustrates that insulin delivery problems can produce unexpected hypoglycemia, but in this scenario the cause is a clear dosing error . The nursing response remains the same: correct the low glucose first using the least invasive route the patient can safely tolerate, then address the error through proper channels.