Insulin Therapy Guidelines

Initial Insulin Regimen Selection

The American Diabetes Association recommends starting with basal insulin at 10 units once daily (or 0.1-0.2 units/kg/day) for type 2 diabetes, and titrating aggressively every 3 days based on fasting glucose until targets are achieved 1, 2, 3
For type 2 diabetes, the initial approach is to begin with basal insulin alone, administering 10 units once daily or 0.1-0.2 units/kg body weight at the same time each day, and continuing metformin (unless contraindicated) and possibly one additional non-insulin agent 1, 2, 3, 4
For type 1 diabetes, basal-bolus therapy is required from diagnosis, with a total daily dose of 0.5 units/kg/day (range 0.4-1.0 units/kg/day), split into 40-60% basal insulin and 40-60% prandial insulin divided before meals 1, 2, 5

The American Diabetes Association recommends injecting subcutaneously into the abdomen, thigh, or deltoid, and rotating injection sites within the same region to prevent lipodystrophy 4
Basal insulin should be administered at the same time every day, any time of day, while rapid-acting insulin should be given 0-15 minutes before meals 1, 4

The target fasting glucose is 80-130 mg/dL, and basal insulin should be titrated aggressively every 3 days based on fasting glucose until targets are achieved 1, 2, 3
If fasting glucose is 140-179 mg/dL, basal insulin should be increased by 2 units every 3 days, and if fasting glucose is ≥180 mg/dL, basal insulin should be increased by 4 units every 3 days 1, 2
Daily fasting glucose monitoring is mandatory during titration, and hypoglycemia should be treated promptly 1, 2, 3

Patients should be educated on self-monitoring of blood glucose, hypoglycemia recognition and treatment, injection technique and site rotation, insulin storage and handling, and "sick day" management rules 1, 2, 3, 4
Patients should understand that type 2 diabetes is progressive and insulin becomes necessary as beta-cell function declines, not due to patient failure 1, 3, 4

Metformin should be continued unless contraindicated, as it reduces insulin requirements, prevents weight gain, and improves cardiovascular outcomes 1, 2, 3, 4
Sulfonylureas should be stopped when advancing beyond basal-only insulin to prevent hypoglycemia, and DPP-4 inhibitors and GLP-1 receptor agonists should be discontinued with complex insulin regimens 1, 2, 3

Sliding scale insulin as monotherapy is condemned by all guidelines, as it treats hyperglycemia reactively rather than preventing it 1, 2, 7
Delaying insulin initiation in patients not achieving goals with oral agents prolongs hyperglycemia exposure, and continuing to escalate basal insulin beyond 0.5-1.0 units/kg/day without adding prandial coverage causes overbasalization with increased hypoglycemia 1, 2, 6

For hospitalized patients, insulin should be started at 0.3-0.5 units/kg/day total (50% basal, 50% bolus) for those eating regular meals, and reduced by 20% if ≥0.6 units/kg/day to prevent hypoglycemia 2
For patients with renal impairment, the total daily dose should be reduced by 50% for CKD Stage 5 with type 2 diabetes, and by 35-40% for CKD Stage 5 with type 1 diabetes, and titrated conservatively with eGFR <45 mL/min/1.73 m² 2