Diabetes Treatment: Type 1 and Type 2
Type 1 Diabetes Treatment
Most people with type 1 diabetes should be treated with multiple daily injections (MDI) of prandial and basal insulin—typically 3-4 injections per day—or continuous subcutaneous insulin infusion (CSII) using an insulin pump. 1, 2
Insulin Regimen Structure
Use rapid-acting insulin analogs (such as insulin aspart, lispro, or glulisine) before meals rather than regular human insulin to reduce hypoglycemia risk, particularly nocturnal hypoglycemia 1, 2
Basal insulin coverage should comprise approximately 50% of total daily insulin dose, with the remaining 50% as prandial insulin, though this varies based on carbohydrate intake patterns 1
Starting insulin dose is typically 0.5 units/kg/day for metabolically stable patients, with a range of 0.4-1.0 units/kg/day depending on clinical circumstances (higher during puberty, pregnancy, or acute illness) 1
Insulin Dose Adjustment
Match prandial insulin doses to three key factors: carbohydrate intake at meals, premeal blood glucose levels, and anticipated physical activity 1, 3, 2
For patients who master carbohydrate counting, consider incorporating fat and protein content into prandial dosing calculations for improved postprandial control 1
Technology Considerations
Automated insulin delivery (AID) systems combining insulin pumps with continuous glucose monitoring should be considered for most individuals with type 1 diabetes to improve time in target range, reduce A1C, and decrease hypoglycemia 1
Continuous subcutaneous insulin infusion (CSII) access should continue after age 65 for patients successfully using this therapy 1
Adjunctive Therapies (Limited Role)
Pramlintide is the only FDA-approved non-insulin adjunctive therapy for type 1 diabetes, though it requires concurrent reduction of prandial insulin to avoid severe hypoglycemia 1, 2
Metformin added to insulin therapy does not significantly improve A1C (reduction of only 0.11%, p=0.42) but may reduce insulin requirements by approximately 6.6 units/day and modestly decrease weight 1, 2
GLP-1 receptor agonists and SGLT2 inhibitors are not FDA-approved for type 1 diabetes and carry increased risk of diabetic ketoacidosis, particularly with SGLT2 inhibitors 1, 2
Type 2 Diabetes Treatment
Metformin is the preferred initial pharmacological agent for type 2 diabetes if not contraindicated and if tolerated, combined with lifestyle modifications including weight loss of at least 5%. 1
Initial Therapy Algorithm
Start metformin at or soon after diagnosis unless contraindicated (can be continued with declining renal function down to GFR 30-45 mL/min with dose reduction) 1
For markedly symptomatic patients with blood glucose ≥300-350 mg/dL or A1C ≥10-12%, consider initiating insulin therapy immediately (with or without additional agents) rather than waiting for metformin titration 1
Combination Therapy Selection
When metformin monotherapy fails to achieve A1C targets within 3 months, add a second agent based on the presence of cardiovascular disease, heart failure, or chronic kidney disease. 1
For patients with established atherosclerotic cardiovascular disease, heart failure, or chronic kidney disease: Add agents proven to reduce cardiorenal risk (GLP-1 receptor agonists or SGLT2 inhibitors) regardless of A1C level 1
For patients requiring weight management: Prioritize GLP-1 receptor agonists, which provide superior weight loss compared to other agents 1
For patients without cardiorenal disease: Choose from sulfonylureas, thiazolidinediones, DPP-4 inhibitors, SGLT2 inhibitors, GLP-1 receptor agonists, or basal insulin based on patient-specific factors including hypoglycemia risk, cost, and side effect profile 1
Insulin Initiation in Type 2 Diabetes
Begin with basal insulin (NPH, glargine, detemir, or degludec) once daily, typically at bedtime, or once-daily premixed insulin 1
Continue metformin when initiating insulin therapy for ongoing glycemic and metabolic benefits, including reduced weight gain and lower insulin requirements 1
Prefer GLP-1 receptor agonists over insulin when possible for better weight outcomes and lower hypoglycemia risk 1
If insulin is used, combine with a GLP-1 receptor agonist for greater efficacy, treatment durability, and favorable effects on weight and hypoglycemia 1
Treatment Intensification
Do not delay treatment intensification when glycemic targets are not met; reassess medication regimen every 3-6 months 1
Avoid overbasalization: If basal insulin doses exceed 0.5 units/kg/day without achieving targets, add prandial insulin rather than continuing to increase basal doses 1
For dual therapy failure: Add a third agent or transition to basal-bolus insulin regimen with rapid-acting insulin at meals 1
Common Pitfalls to Avoid
Clinical inertia: Failing to intensify therapy when A1C remains above target for more than 3 months is a major barrier to optimal outcomes 1
Abrupt discontinuation of oral medications: When starting insulin, continue oral agents (particularly metformin) to avoid rebound hyperglycemia 4
Ignoring cardiovascular risk: In patients with established cardiovascular disease or high risk, prioritize cardioprotective agents (GLP-1 RA or SGLT2 inhibitors) over glycemic control alone 1