Insulin Therapy Guidelines

Introduction to Insulin Therapy

The American Diabetes Association recommends insulin therapy for patients with type 1 diabetes and those with type 2 diabetes who have not achieved adequate glycemic control with other agents 1
Insulin therapy encompasses multiple formulations with distinct pharmacokinetic profiles, ranging from ultra-rapid-acting analogs to long-acting basal insulins, each designed to address specific glycemic patterns throughout the day 1

Insulin lispro, aspart, and glulisine have an onset of 5-15 minutes, peak of 1-2 hours, and duration of 3-5 hours 2, 3
Regular (short-acting) insulin has an onset of 30 minutes, peak of 2-4 hours, and duration of 6-8 hours 2, 5
NPH (Neutral Protamine Hagedorn) insulin has an onset of 1-2 hours, peak of 4-6 hours, and duration of 12-18 hours 2, 5
Insulin glargine and detemir have a duration of 18-24 hours, with a relatively peakless profile 2
Insulin degludec has an ultra-long duration of more than 42 hours, providing the most stable basal coverage 7

The American Diabetes Association recommends starting with basal insulin at 10 units daily or 0.1-0.2 units/kg/day, continuing metformin for ongoing metabolic benefits 1, 7
For type 1 diabetes, automated insulin delivery (hybrid closed-loop) systems are the preferred regimen, providing the highest flexibility and lowest hypoglycemia risk 3, 4
For type 2 diabetes, the initial regimen should include basal insulin, with the option to add prandial insulin or a GLP-1 receptor agonist if necessary 1, 7

Insulin must be injected subcutaneously, never intramuscularly, to ensure predictable absorption 3, 4
Approved injection sites include the abdomen, thigh, buttock, and upper arm, with the abdomen providing the fastest absorption 3, 4
A systematic rotation protocol within one anatomical area is recommended to prevent lipohypertrophy and erratic absorption 7, 9

Blood glucose monitoring is integral to insulin therapy and must be performed regularly, with a focus on fasting and postprandial glucose levels 1, 7
Continuous glucose monitoring (CGM) is superior to blood glucose monitoring and improves outcomes with all insulin regimens 3, 4
HbA1c monitoring should be performed every 3 months until target is achieved, then every 3-6 months 1, 7

In patients with renal impairment, lower insulin doses are required, and titration should be based on clinical response with increased hypoglycemia vigilance 1
For steroid-induced hyperglycemia, NPH insulin administered concomitantly with morning glucocorticoid dose is the standard approach 6
In hospital settings, critically ill patients require IV insulin infusion, while non-critically ill patients can use subcutaneous insulin with a target glucose range of 140-180 mg/dL 7

Overbasalization can be avoided by adding prandial insulin or a GLP-1 receptor agonist rather than continuing to increase basal dose 8
Therapeutic inertia should be avoided by reassessing and modifying the regimen every 3-6 months, without delaying intensification when goals are unmet 1, 8

Patient education is crucial and should include hypoglycemia recognition and treatment, glucagon administration, injection technique, and sick day management 7, 9
Dose adjustment principles should be based on basal insulin, prandial insulin, and correction insulin, with adjustments made according to glucose levels and insulin sensitivity factor 2, 5
Cost considerations should be taken into account when choosing basal insulin, with a focus on person-specific considerations, including cost 1