The Difference Between Basal and Bolus Insulin

Vials of insulin.
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If you have diabetes, two types of insulin, basal insulin and bolus insulin, help you maintain an optimal blood sugar level, replicating the body's normal function as closely as possible. Basal insulin, also referred to as background insulin, regulates your glucose levels in between meals, and bolus insulin is extra insulin needed to manage your glucose levels after a meal.

Background Insulin and Bursts of Insulin

The body needs insulin for glucose management and metabolism. When you eat, your food is digested and converted into glucose (sugar) so it can be used for energy. Every cell in the body needs energy from glucose to function properly. Some of the glucose from food is used immediately by the cells, and some is stored in the liver as glycogen, a reserve molecule that is used later for energy.

Insulin is needed to store excess glucose in the liver and to transfer it from the blood to the cells, where it is needed for energy.

Bursts of Insulin

The pancreas secretes more insulin right after a meal to manage the rapid increase of blood glucose that comes from food. This process quickly returns blood glucose to normal levels after eating.

Background Insulin

Between the glucose that is consumed through food and the glucose that is gradually released from the liver, the body gets a constant supply of glucose. In addition to the insulin release after a meal, the pancreas also constantly makes and releases a small amount of insulin into the blood to help manage the regular release of stored glucose in between meals. Basal insulin, the background insulin that is normally supplied by the pancreas, is released 24 hours a day, whether or not a person eats.

Basal and Bolus Insulin in Diabetes

If you have type 1 diabetes, the beta cells of the pancreas that normally produce the insulin have largely shut down. Both your basal insulin and your bolus insulin must be obtained through injections or from an insulin pump in order to process all of the glucose taken in through food or released by the liver.

Type 2 diabetes, which is characterized by a decreased cellular response to insulin, rather than a decrease in insulin itself, may also require insulin treatment, although this treatment is not as common as it is with type 1 diabetes.

Bolus insulin replaces the extra insulin the pancreas would naturally make in response to glucose taken in through food. The amount of bolus insulin needed depends on the size of the meal. Basal insulin replaces the background insulin that your body would normally make between meals to maintain constant blood glucose levels.

Types of Basal and Bolus Insulins

Long-acting basal insulins include NPH (neutral protamine Hagedorn), Levemir (detemir), and Lantus (glargine). They begin working within two hours after injection and are released slowly, lasting up to 24 hours to provide the background insulin that is needed around the clock.

Fast-acting bolus insulins, such as NovoLog, Apidra, Humalog, and Regular, generally begin working within 15 minutes. The exception is Regular, which has an onset of about 30 minutes. Each of these bolus insulins is designed to be taken just before a meal and to have a duration of up to five hours for NovoLog, Apidra, and Humalog, and seven hours for Regular.

This means that a person with type 1 diabetes would have to take multiple injections of bolus insulin each day to cover meals and snacks, along with basal insulin to keep the glucose in check.

Basal and Bolus Insulin With Insulin Pumps

An insulin pump would typically provide a constant low dose of fast-acting insulin that would act as the basal background insulin. Before meals, you would take a larger dose of fast-acting insulin to cover the anticipated caloric intake. This satisfies both the basal and bolus needs using the same fast-acting insulin.

A Word From Verywell

Whether you are planning on injecting your insulin with a syringe or using an insulin pump, you would begin by discussing your options with your doctor or dietician. The type of insulin most likely to control your blood sugar depends on a number of factors, including your typical blood sugar, your lifestyle, and how busy you are.

Your dose and schedule will be calculated with a healthcare professional, who will also make sure that you know how to measure the insulin, how to calculate the amount of insulin you need, and how to increase or decrease your dose if you eat more or less than anticipated during a meal or snack. And last, but often very important in managing diabetes, dietary guidelines will be discussed so that you can maintain a healthy blood sugar level, good nutrition, and a healthy weight.

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