Final answer:
A patient should administer short-acting insulin before meals and eat 15 minutes after injection for optimal glucose control.
Step-by-step explanation:
When administering short-acting insulin with a peak effect of 15 minutes, it is generally recommended that the patient should inject insulin before meals. After taking the insulin injection, it is best to wait for 15 minutes before eating. Therefore, the correct answer to when a patient should administer short-acting insulin and when it is recommended to eat after injection is: Before meals; 15 minutes after injection. This timing is suggested because the peak action of insulin coincides with the increase in blood glucose levels from the meal, allowing for optimal glucose control.