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The Basal/Bolus Insulin Regimen

As previously discussed in Unit 1: “Type 1 Diabetes”, the goal of insulin therapy in Type 1 diabetes mellitus is to mimic the physiologic production of insulin by the pancreas.  This can be approximated using a basal/bolus insulin regimen, as depicted in Figure 2.

Figure 2 – The dark yellow represents a normal physiologic insulin profile throughout the day with post-prandial insulin spikes at 10 am, 2 pm, and 8 pm due to carbohydrate ingestion at mealtimes (breakfast, lunch, and dinner). A rapid-acting insulin is strategically administered as a bolus (represented by the bold, blue lines) 15 minutes before meals to achieve paired timing of insulin action with the absorption of carbohydrates (discussed further in “Rapid-acting insulins”). Additional rapid-acting insulin may also be administered at these times to correct for pre-prandial hyperglycemia to bring post-prandial blood sugars down into the goal glycemic range (most often 70-150mg/dL) within 2 hours after a meal. Note that overnight, while sleeping and fasting between meals, glucose production still occurs due to the release of glucose from glycogen stores in the liver. Thus, basal insulin is also needed (represented by the bold, black line). Image Attribution:  “Basal/bolus regimen mimics normal insulin profile” by Magaji and Johnston (2011) BY License for non-commercial reuse, Version 1.0

Basal insulin covers background/basal glucose release from the liver. This hepatic glucose production usually occurs to maintain normal blood glucose during fasting. Pancreatic insulin production never drops to zero, so in patients who are insulin deficient, basal insulin administration mimics the basal insulin production from the pancreas to maintain control over hepatic glycogenolysis.

  • The method of basal insulin delivery dictates what type of insulin is used as the “basal insulin.”  Basal insulin delivery is accomplished either by:
    1. The administration of long-acting injectable insulin when using multiple daily injections
    2. Through the programmed delivery of a continuous, low-rate infusion of rapid-acting insulin when using insulin pump [CSII] therapy.

A bolus is the administration of a single, usually larger dose of short- or rapid-acting insulin.

Bolus insulin is used:

  1. Cover spikes in blood glucose due to ingestion of carbohydrates/glucose from food
  2. As needed to:
    1. Bring high blood sugars back into a normal range
    2. Treatment of ketonemia (or ketonuria)

Administration of bolus insulin occurs by giving:

  1. A single injection of rapid-acting insulin is given via syringe or insulin pen when using multiple daily injections.
  2. Alternatively, boluses can be delivered by an insulin pump when the user directs the pump to “push” the desired amount of rapid-acting insulin over a short time (seconds to minutes).

Other insulin regimens exist that involve combinations of other types of insulin (aside from rapid-acting and basal insulin), but these go beyond the scope of this book.

Also, remember that the classic basal/bolus regimen may not be necessary for treating Type 2 diabetes depending on the initial severity of their presentation and ability to achieve A1c goals over time.

Quiz Yourself:

Bibliography:

  1. Vasudev Magaji, Jann M. Johnston; Inpatient Management of Hyperglycemia and Diabetes. Clin Diabetes 1 January 2011; 29 (1): 3–9. https://doi.org/10.2337/diaclin.29.1.3

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General Inpatient Management of Pediatric Diabetes Mellitus at University of Iowa Stead Family Children's Hospital Copyright © 2023 by Alex Tuttle is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.

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