What is Basal Insulin?
Basal insulin refers to longer-acting insulin formulations designed to cover the body's basal metabolic insulin requirement by regulating hepatic glucose production throughout the day and night, in contrast to bolus or prandial insulin which manages glycemic excursions after meals. 1
Physiologic Role and Mechanism
Basal insulin provides relatively uniform insulin coverage between meals and during sleep, with its principal action being to restrain hepatic glucose production and limit hyperglycemia overnight and between meals. 1 This mimics the sustained baseline insulin secretion pattern of healthy pancreatic beta cells, which normally maintain steady insulin levels throughout the day, separate from the meal-related insulin bursts. 2, 3
Available Formulations
Intermediate-Acting Options
- NPH insulin can be administered once or twice daily and represents the traditional intermediate-acting basal insulin option. 1
Long-Acting Insulin Analogs
- Insulin glargine is available as U-100 or U-300 formulations, administered once daily. 1
- Insulin detemir is administered once or twice daily. 1
- Insulin degludec is available as U-100 or U-200 formulations, administered once daily. 1
Clinical Advantages and Considerations
Long-acting insulin analogs (degludec, glargine, detemir) demonstrate a modestly lower absolute risk for hypoglycemia compared with NPH insulin, particularly nocturnal hypoglycemia, though they cost more. 1 However, in real-world settings where patients are treated to conventional treatment targets, initiation of NPH compared with detemir or glargine U-100 did not increase hypoglycemia-related emergency department visits or hospital admissions. 1
When comparing human and analog insulins, cost differences can be large while differences in hypoglycemia risk are modest and differences in glycemic efficacy minimal. 1
Role in Treatment Algorithms
Basal insulin is the preferred initial insulin formulation in patients with type 2 diabetes. 1 It can be added to metformin and other oral agents, with starting doses estimated based on body weight (0.1-0.2 units/kg/day) and the degree of hyperglycemia. 1
The effectiveness of basal insulin is highly dependent on appropriate use, patient selection and training, dose adjustment for changes in diet, activity, or weight, and titration to acceptable, safe glucose targets. 1 The way insulin is administered—including dose, timing of injection, and glycemic targets—has a greater impact on adverse effects than differences among insulin formulations. 1
When Basal Insulin Alone Is Insufficient
Although the majority of patients with type 2 diabetes requiring insulin therapy can be successfully treated with basal insulin alone, some will require prandial insulin therapy with shorter-acting insulins due to progressive diminution in their insulin secretory capacity. 1 When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, adding prandial insulin becomes more appropriate than continuing to escalate basal insulin alone. 1