Insulin Dosing Guidelines
Initial Dosing Strategy
For insulin-naive patients with type 2 diabetes, start basal insulin at 10 units once daily or 0.1-0.2 units/kg body weight, administered at the same time each day. 1, 2 For patients with severe hyperglycemia (blood glucose ≥300-350 mg/dL or A1C ≥10%), consider higher starting doses of 0.3-0.5 units/kg/day as total daily dose, split between basal and prandial insulin. 1, 3
For type 1 diabetes, the total daily insulin requirement typically ranges from 0.4-1.0 units/kg/day, with 0.5 units/kg/day being standard for metabolically stable patients. 2 Divide this as approximately 50% basal insulin and 50% prandial insulin distributed among three meals. 1, 2
Evidence-Based Titration Algorithm
Increase basal insulin by 2 units every 3 days if fasting glucose is 140-179 mg/dL, or by 4 units every 3 days if fasting glucose is ≥180 mg/dL, until reaching target of 80-130 mg/dL. 1, 2 This systematic approach prevents prolonged hyperglycemia while minimizing hypoglycemia risk. 1
If hypoglycemia occurs without clear cause, immediately reduce the dose by 10-20%. 1, 2 Daily fasting blood glucose monitoring is essential during titration. 1, 2
Critical Threshold: Recognizing Overbasalization
When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, add prandial insulin rather than continuing to escalate basal insulin alone. 1, 2 Clinical signals of overbasalization include:
- Basal insulin dose >0.5 units/kg/day 1, 2
- Bedtime-to-morning glucose differential ≥50 mg/dL 1, 2
- Hypoglycemia episodes 1
- High glucose variability 1
Continuing to increase basal insulin beyond this threshold leads to suboptimal control and increased hypoglycemia risk without meaningful improvement in fasting glucose. 1, 2
Adding Prandial Insulin Coverage
Start with 4 units of rapid-acting insulin before the largest meal or 10% of the current basal insulin dose. 1, 2 Prandial insulin should be added when:
- Fasting glucose reaches target but A1C remains above goal after 3-6 months of basal insulin optimization 1
- Significant postprandial glucose excursions occur (>180 mg/dL) 1
- Basal insulin approaches 0.5-1.0 units/kg/day without achieving glycemic targets 1, 2
Titrate prandial insulin by 1-2 units or 10-15% every 3 days based on postprandial glucose readings. 1, 2
Foundation Therapy Considerations
Continue metformin unless contraindicated when initiating or intensifying insulin therapy. 1, 2 Metformin reduces total insulin requirements and provides complementary glucose-lowering effects. 2, 4
Consider adding a GLP-1 receptor agonist to basal insulin if not already prescribed, as this combination improves A1C while minimizing weight gain and hypoglycemia risk compared to intensified insulin regimens alone. 1, 2
Special Clinical Situations
For severe hyperglycemia (blood glucose ≥300-350 mg/dL, A1C ≥10-12% with symptoms), initiate basal-bolus therapy immediately rather than basal insulin alone. 1, 3 Start with 0.3-0.5 units/kg/day total daily dose, giving half as basal insulin and half as prandial insulin divided among meals. 2, 3
For hospitalized patients on high-dose home insulin (≥0.6 units/kg/day), reduce the total daily dose by 20% upon admission to prevent hypoglycemia. 2 Lower doses (0.1-0.25 units/kg/day) are recommended for high-risk patients including elderly (>65 years), those with renal failure, or poor oral intake. 2
Administration Guidelines
Administer basal insulin at the same time each day, with timing dependent on the patient's schedule. 1, 2 Inject subcutaneously in the thigh, abdominal wall, or upper arm, rotating sites within the same region. 5 The shortest needles (4-mm pen, 6-mm syringe) are safest, most effective, and less painful. 4
Do not mix or dilute insulin glargine with other insulin preparations due to its low pH. 2, 5
Common Pitfalls to Avoid
Never delay insulin initiation in patients not achieving glycemic goals with oral medications. 1, 2 Many months of uncontrolled hyperglycemia should be specifically avoided. 1
Do not rely on correction insulin (sliding scale) alone without scheduled basal and prandial insulin—this approach is associated with poor glycemic control and increased complications. 3
Avoid continuing to escalate basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this leads to overbasalization with increased hypoglycemia risk. 1, 2
Do not abruptly discontinue oral medications when starting insulin due to risk of rebound hyperglycemia. 4
Monitoring Requirements
Assess adequacy of insulin dose at every clinical visit, looking for signs of overbasalization. 1, 2 Reassess and modify therapy every 3-6 months to avoid therapeutic inertia. 2 During active titration, reassess every 3 days. 1, 2