MD Notes

creation date: 2025-11-28 09:17
tags: Pharmacology

Insulin

Background

Insulin is a peptide hormone secreted by the pancreas (beta cells). Use of exogenous insulin is indicated when there is inadequate production of endogenous insulin.

Insulin binds to insulin receptors on the plasma membranes throughout the body. Generally, insulin activity causes the translocation of glucose transporters to the membrane resulting in the influx of glucose from the blood into the cell.

Additionally, insulin causes the following effect depending on the cell type:

  • Hepatic cells: promotes glycogenesis, inhibits gluconeogenesis
  • Adipocytes: promotes lipogenesis, inhibits lipolysis
  • Muscle cells: promotes glycogenesis and protein synthesis, inhibits protein catabolism
  • Pancreatic beta cells: inhibits glucagon release
  • Brain cells: involved in appetite regulation

Dosing

Starting Dose

A simplified regimen is:

  • Total daily insulin (TDI) = ~0.4 units/kg
    • Basal/long acting = 1/2 TDI
    • Short acting before each meal = (1/2 TDI)/3 for each of 3 meals

Titration

The dosing is then adjusted based on serum glucose levels (adjusting the levels of each meal) and basal levels.

Goal is to minimize hypoglycemia while managing glucose levels.

Sliding Scale

In the hospital, a sliding scale insulin regimen is common as an adjunct to a basal-postprandial regimen. This is a reactive insulin administration based on the blood glucose.

Types

Rapid-Acting

Characteristics
  • Peak: 1 hr
  • Duration: 3-4 hrs
Use
  • Pre-prandial bolus
Examples
  • Insulin aspart (Fiasp, NovoLog)
  • Insulin glulisine (Apidra)
  • Insulin lispro (Ademelog, Humalog, Lyumjev)

Short-Acting

Characteristics
  • Peak: 2-3 hrs
  • Duration: 4-6 hrs
Use
  • Pre-prandial bolus
Examples
  • Regular insulin (IV)

Intermediate-Acting

Characteristics
  • Peak: 6-10 hrs
  • Duration: 10-16 hrs
Use
  • Basal insulin (BID)
Examples
  • NPH

Long-Acting

Characteristics
  • Peak: none
  • Duration: 24 hrs
Use
  • Basal insulin (once daily PM post-prandial)
  • Used as basal in hospital
Examples
  • Insulin glargine (Lantus)
  • Insulin detemir (Levemir)

Ultralong-Acting

Characteristics
  • Peak: none
  • Duration: 36+ hrs
Use
  • Basal insulin
Examples
  • Insulin icodec (Awiqli) - once weekly

References

Tools / Guidelines

Diabetes Canada - Insulin Prescribing

Additional Reading

Backlinks