Basal-Bolus Approach MDI or PUMP

Adjusting Insulin: a basal-bolus approach

The terms “basal” and “bolus” are used both in injected insulin and pump programs. But what exactly is a Basal-Bolus approach to insulin adjustment? How is basal insulin different from bolus insulin? Here we'll explain the theory behind adjusting insulin in both Multiple Daily Injection (MDI) as well as Insulin Pump Therapy programs.

What’s the Difference Between Basal and Bolus?

In an intensive insulin program, a differentiation is made between basal and bolus insulin.

"Basal"

Basal insulin is the background insulin which keeps blood glucose steady in the absence of food and exercise. A healthy pancreas secretes a small amount of basal insulin into the bloodstream every few minutes, to match the small amounts of glucose released by the liver on a continuous basis, so that glucose can be used by the body’s cells for basic energy needs. In this way, basal insulin offsets internal sources of glucose (rather than covering the foods we eat, which are an external glucose source).

For individuals with type 1 diabetes on a Multiple Daily Injections (MDI) program, basal insulin is provided by injecting “peakless” long-acting insulin (such as Lantus® or Levemir®).

For individuals with type 1 diabetes and on an Insulin Pump program, basal insulin is provided by infusing rapid-acting insulin (such as Humalog®, Novorapid®, or Apidra®) in tiny doses every few minutes.

"Bolus"

Bolus insulin is a dose of rapid-acting insulin which is delivered either to:

  • cover the carbohydrate-containing food which we eat. This is called a “carb bolus” (or “bolus for carbs”) and is specified by an Insulin-to-Carb (I:C) Ratio.
  • correct high blood glucose. In this case, the bolus is called a “correction bolus” and is specified by some variation of an Insulin Sensitivity Factor (ISF), such as a Correction Formula, Sliding Scale, or ISF setting on a pump.

Bolus insulin is provided by rapid-acting insulin in both MDI and pump programs, either injected via syringe/pen or infused via an insulin pump, respectively.

Does my child need the same amount of insulin at all times?

Both basal and bolus insulin needs vary from person to person, and may be different at different times of the day. That is, your child may:

  • need more basal insulin in the morning than in the afternoon. This variation can be accommodated with different programmed settings if your child uses an insulin pump; on injected insulin programs the strategy is to find the “best fit” for the daily (or twice daily) dose of basal insulin.
  • have a different I:C ratio for breakfast than for lunch or supper. Children typically need more insulin to cover their breakfast carbs (as compared to other meals).
  • have different insulin sensitivity at different times of the day. You may find that a larger correction dose is needed in the early morning than is needed in the afternoon, for example.

For more detailed information and practice exercises:

An excellent in-depth but easy-to-understand self-learning program on insulin dose adjustment for parents of children with diabetes is provided online by BC Children’s Hospital. To access this resource, we encourage you to visit their website.

Next Steps in adjusting insulin in an MDI program:

Assessing Basal Insulin Doses

References:

The above information was adapted with permission from The Alberta Children’s Hospital Diabetes Clinic information handouts.

The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.

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