The insulin injected before a meal is usually mealtime insulin. If you forget to inject a fast-acting insulin analogue before a meal, you can make up the injection after the meal. The fast-acting insulin analogues have a fast onset of action, about 15 minutes after subcutaneous injection, and can be injected immediately before or even immediately after a meal, without the need to inject 30 minutes before the meal, and reach the peak more quickly. If short-acting human insulin is forgotten to be injected before meal, it is usually not advisable to inject after meal, and close monitoring of blood glucose is required. Human insulin has a slower onset of action and is usually injected subcutaneously 30 minutes before meal. If injected after a meal, it can easily lead to hypoglycemia before the next meal.