Bolus insulin is an insulin dosage that is given in the form of an injection for the purposes of short-acting and rapid-acting results. In patients with type 1 diabetes, different types of insulin are given. The long-acting insulin is given for ensuring a steady regulation of insulin levels. This is called basal insulin. This ensures that the blood sugar levels are stable. Short-acting insulin on the other hand is given as a single dose specifically during meal times in order to ensure blood sugar control. This is called bolus insulin. In people without diabetes, the pancreas normally makes insulin in response to the food consumed as it contains glucose. This level of insulin secretion depends upon the size of the meal. However, in people with type 1 diabetes, the pancreas does not produce insulin. This is due to beta cell destruction. In order to compensate for this loss of insulin, a bolus insulin dosage is given prior to the consumption of meals so that there is availability of insulin to absorb the glucose generated from the food digested. Injecting a bolus insulin dosage ensures the normalcy of blood sugar levels. Bolus insulin comes in two types – short-acting insulin, and rapid-acting insulin. The difference among the two lies in the speed of action, the duration of onset action, the speed at which insulin enters the bloodstream, and the time taken to reach peak action. In the case of short-acting insulin, the blood sugar levels are reduced in a period of half an hour, and rapid-acting insulin reduces blood sugar levels in a span of 15 minutes. Short-acting insulins take around 15 minutes to start onset action, reaches peak action in a duration of two to four hours, and acts totally for a time period of five to eight hours. Rapid-acting insulins take around five to 15 minutes for onset action, reaches peak action in a duration of 30 to 90 minutes, and lasts for a duration of three to five hours. Bolus insulin is given to cover for the carbohydrate consumption. That is the reason the bolus insulin dosage is calculated as an insulin to carbohydrate ratio. It is the number of grams of carbohydrate covered by one unit of insulin. Normally, 12 to 15 grams of carbohydrate content in the food requires one unit of rapid-acting insulin; however, the range of carbohydrate varies up to 5 grams depending upon a person’s insulin sensitivity, the time of the day, physical activity, and stress levels. The general insulin requirement for a bolus insulin dosage is calculated in terms of carbohydrate coverage insulin dose in meal and high blood sugar correction dose. The carbohydrate coverage insulin dose is the total grams of carbohydrate in the meal divided by the grams of carbohydrate disposed by one unit of insulin. High blood sugar correction dose is calculated by dividing the difference between the actual blood sugar level and the target blood sugar level with the insulin sensitivity factor. The insulin sensitivity factor is the amount of blood sugar level reduced by one unit of insulin. So, the total mealtime insulin dosage would be the carbohydrate coverage insulin dose plus the high blood sugar correction dose.