Insulin Therapy in Type 1 Diabetes

Introduction to Insulin Regimens

• The American Diabetes Association recommends a basal-bolus regimen with initial dosing of 0.5 units/kg/day, with approximately 50% as basal insulin and 50% as prandial insulin, adjusted based on blood glucose monitoring and individual needs, with higher doses possibly required during puberty, pregnancy, or medical illness 1, 2, 3, 4
• Intensive insulin therapy is the primary treatment for Type 1 diabetes, delivered through either multiple daily injections (MDI) of prandial and basal insulin or continuous subcutaneous insulin infusion (CSII) via insulin pump, as recommended by the American Diabetes Association 2, 3, 5, 6, 4, 7

Basal Insulin Titration

• Assess adequacy of basal insulin dose at every visit, and evaluate for overbasalization by checking elevated bedtime-to-morning glucose differential, elevated postprandial-to-preprandial differential, hypoglycemia, and high glucose variability 8
• Initial dosing for metabolically stable patients is 0.5 units/kg/day (range: 0.4-1.0 units/kg/day), with higher insulin requirements needed during puberty, pregnancy, and medical illness 2, 3, 4

Prandial Insulin Titration

• Initial prandial dosing is 4 units per day or 10% of basal insulin dose, with titration increasing by 1-2 units or 10-15% based on postprandial glucose values, and adjustment factors matching prandial insulin to carbohydrate intake, pre-meal blood glucose levels, and anticipated physical activity 8, 3, 4, 7, 9
• For advanced patients, consider fat and protein content of meals in prandial dosing calculations, in addition to carbohydrate intake and pre-meal blood glucose levels 1, 3, 4, 7, 9

Hypoglycemia Management

• For hypoglycemia, determine cause, and if no clear reason, lower corresponding dose by 10-20% 8
• Treat hypoglycemia with 15-20g of glucose (preferably glucose tablets) and recheck blood glucose after 15 minutes, repeating treatment if hypoglycemia persists, and prescribe glucagon for all individuals taking insulin and educate family members and caregivers on glucagon administration 6, 7, 9

Insulin Administration

• Three to four injections per day of basal and prandial insulin can be used, with insulin analogs recommended to reduce hypoglycemia risk 5, 2, 3, 4, 7
• The American College of Endocrinology recommends continuous subcutaneous insulin infusion (CSII) via insulin pump, which provides a slight advantage over multiple daily injections (MDI) in HbA1c reduction (-0.30% difference) and reduces rates of severe hypoglycemia, with sensor-augmented pumps having low glucose suspend features that can reduce nocturnal hypoglycemia 10

Special Considerations

• Consider sensor-augmented pumps with low glucose suspend features for patients not meeting glycemic targets or experiencing frequent/severe hypoglycemia 8, 3, 10, 11, 4
• Approximately 5-10% of patients diagnosed with type 1 diabetes may have negative islet antibody tests, indicating a different pathophysiology, but still require insulin therapy due to insulin deficiency, according to the American Diabetes Association 12
• Patients with type 1 diabetes should be screened for associated conditions such as thyroid dysfunction, vitamin B12 deficiency, and celiac disease, even in patients with negative islet antibodies, based on moderate-strength evidence 10

Adjunctive Therapies

• Pramlintide, an injectable amylin analog, can be used as an adjunct to mealtime insulin, and metformin may be considered in overweight/obese patients with poorly controlled type 1 diabetes to reduce insulin requirements 4, 5, 3
• GLP-1 receptor agonists, DPP-4 inhibitors, and SGLT2 inhibitors are currently not FDA-approved for type 1 diabetes but are being studied, with potential benefits including weight reduction, modest improvement in glycemic control, reduced insulin requirements, and possible cardiovascular benefits 5, 3, 4

Glycemic Targets and Monitoring

• The American Diabetes Association recommends target HbA1c levels of <7% for most adults with type 1 diabetes, with HbA1c testing at least twice per year in patients meeting treatment goals and quarterly testing in those whose therapy has changed or who are not meeting glycemic goals, based on moderate-strength evidence 4
• Target HbA1c < 7% for most adults, and < 7.5% for children with T1DM, with the goal of minimizing glycemic variability and hypoglycemia risk 13
• Blood glucose monitoring is essential for effective insulin therapy, with fasting plasma glucose values used to titrate basal insulin and both fasting and postprandial glucose values used to titrate mealtime insulin, based on high-strength evidence 4

Patient Education and Treatment Plans

• Patients should be educated on matching prandial insulin to carbohydrate intake, pre-meal blood glucose levels, and anticipated physical activity, as well as carbohydrate counting, fat and protein gram estimation, and sick day management 2, 5, 6, 3, 4, 7, 9
• Insulin treatment plans should be reevaluated every 3-6 months, according to the American College of Endocrinology 10
• Avoid sliding-scale insulin as the sole treatment strategy 10, 11

Therapy Comparison