Between 1500 and 1700: Regular insulin’s duration extends up to 6–8 hours, but its pharmacodynamic activity is weakest during the late phase. By mid-afternoon, serum insulin levels have declined substantially, making hypoglycemia unlikely unless additional factors such as excessive exercise or skipped meals are involved.

Between 1200 and 1400: By this time, regular insulin is nearing the end of its effective window, with plasma levels falling as it is metabolized. While mild hypoglycemia is still possible in sensitive clients, this period does not correlate with the drug’s peak activity and is not the highest-risk interval.

Between 0900 and 1100: Regular insulin peaks about 2–4 hours after administration, producing its maximum glucose-lowering effect during this period. Insulin-driven cellular uptake of glucose is highest, increasing the likelihood of symptomatic hypoglycemia, especially without adequate carbohydrate intake.