Your patient takes regular insulin and NPH twice a day for glucose control. When should they be taught to be alert for signs of hypoglycemia?

The correct time for the patient to be alert for signs of hypoglycemia is late afternoon and early morning due to the pharmacokinetics of the insulins being used.

Regular insulin has a rapid onset and is designed to cover glucose levels during meal times, typically peaking around 2 to 4 hours after administration. NPH (Neutral Protamine Hagedorn) insulin, being an intermediate-acting insulin, has a delayed onset with a peak effect around 4 to 6 hours after injection. The combination of these two types of insulin, especially when taken twice a day, increases the risk of hypoglycemia during the periods following their peak action.

In the context of the dosing schedule likely used with twice-daily injections, the late afternoon would be a time when levels of NPH insulin begin to decrease, but if there's been unexpected activity or insufficient carbohydrate intake, hypoglycemia could occur. Early morning is another critical time as NPH may still be present in circulation, potentially lowering glucose levels before breakfast if the patient did not consume enough food or if there was an unaccounted factor like increased physical activity.

In contrast, the other options do not align as well with this pattern of action for the insulins involved.