Short-Acting Insulin Management in Hospitalized Patients
Core Principle: Abandon Sliding-Scale Monotherapy
Sliding-scale insulin used as the sole regimen is explicitly condemned by all major diabetes guidelines and must be immediately discontinued in favor of scheduled basal-bolus therapy. Only approximately 38% of patients on sliding-scale alone achieve mean glucose <140 mg/dL, versus 68% with scheduled basal-bolus regimens, without increased hypoglycemia when properly implemented. 1
Initial Dosing Strategy
For Insulin-Naïve or Low-Dose Patients
Start with a total daily dose (TDD) of 0.3–0.5 units/kg/day, divided 50% as basal insulin (once daily) and 50% as prandial insulin (split among three meals). 1
Example for a 70 kg patient:
- TDD = 0.4 units/kg × 70 kg = 28 units/day
- Basal insulin (glargine/detemir): 14 units once daily at bedtime
- Prandial insulin (lispro/aspart/glulisine): 14 units total → approximately 5 units before each meal (breakfast, lunch, dinner)
For High-Risk Patients
Use lower starting doses of 0.1–0.25 units/kg/day for:
Example for an 80 kg elderly patient:
- TDD = 0.15 units/kg × 80 kg = 12 units/day
- Basal: 6 units once daily
- Prandial: 2 units before each meal
For Patients on High-Dose Home Insulin
Reduce the total daily dose by 20% upon hospital admission if the patient was receiving ≥0.6 units/kg/day at home. 1
Timing of Short-Acting Insulin Administration
Administer rapid-acting insulin (lispro, aspart, glulisine) 0–15 minutes before meals—ideally immediately before eating—for optimal postprandial glucose control. 1, 2
Never give rapid-acting insulin at bedtime as a sole correction dose, as this markedly increases the risk of nocturnal hypoglycemia. 1
Titration Protocols
Prandial Insulin Titration
Increase each meal dose by 1–2 units (approximately 10–15%) every 3 days based on the 2-hour postprandial glucose reading. 1
Target postprandial glucose: <180 mg/dL 1
Example titration schedule:
- Days 1–3: Give 5 units lispro before lunch; measure 2-hour postprandial glucose daily
- Day 4: If average postprandial glucose >180 mg/dL → increase lunch dose to 6–7 units
- Days 4–6: Continue monitoring
- Day 7: Reassess and adjust again if needed
Basal Insulin Titration (Concurrent Management)
Increase basal insulin by 2 units every 3 days if fasting glucose is 140–179 mg/dL; increase by 4 units every 3 days if fasting glucose ≥180 mg/dL. 1
Target fasting glucose: 80–130 mg/dL 1
Correction (Supplemental) Insulin Dosing
Correction insulin must always supplement—never replace—scheduled basal and prandial doses. 1
Simplified Sliding Scale (Adjunct Only)
Add the following to scheduled prandial doses:
- Pre-meal glucose >250 mg/dL → add 2 units rapid-acting insulin 1
- Pre-meal glucose >350 mg/dL → add 4 units rapid-acting insulin 1
Example: If a patient is scheduled for 5 units lispro before lunch and pre-meal glucose is 280 mg/dL:
- Give 5 units (scheduled) + 2 units (correction) = 7 units total
Individualized Correction Dosing
Calculate Insulin Sensitivity Factor (ISF) = 1500 ÷ TDD 1
Correction dose = (Current glucose – Target glucose) ÷ ISF 1
Example for a patient on 40 units/day TDD:
- ISF = 1500 ÷ 40 = 37.5 mg/dL per unit
- If current glucose is 250 mg/dL and target is 120 mg/dL:
- Correction = (250 – 120) ÷ 37.5 = 3.5 units (round to 3–4 units)
Glucose Monitoring Requirements
For patients eating regular meals:
- Check glucose before each meal and at bedtime (minimum 4 times daily) 1
For patients with poor oral intake or NPO:
- Check glucose every 4–6 hours 1
During active titration:
- Measure 2-hour postprandial glucose after each meal to guide prandial adjustments 1
- Measure fasting glucose daily to guide basal adjustments 1
Critical Threshold: When to Stop Basal Escalation
When basal insulin approaches 0.5–1.0 units/kg/day without achieving glycemic targets, stop further basal increases and add or intensify prandial insulin instead. 1
Clinical signals of "over-basalization":
- Basal dose >0.5 units/kg/day 1
- Bedtime-to-morning glucose differential ≥50 mg/dL 1
- Episodes of hypoglycemia despite overall hyperglycemia 1
- High glucose variability throughout the day 1
Example: For a 70 kg patient, stop escalating basal insulin beyond approximately 35–70 units/day and focus on prandial coverage.
Hypoglycemia Management
Treat any glucose <70 mg/dL immediately with 15 grams of fast-acting carbohydrate, recheck in 15 minutes, and repeat if needed. 1
If hypoglycemia occurs without an obvious cause, reduce the implicated insulin dose (basal or prandial) by 10–20% immediately before the next administration. 1
Example: If a patient experiences hypoglycemia 2 hours after lunch while on 6 units lispro:
- Reduce lunch lispro to 5 units (approximately 17% reduction)
- Continue monitoring closely
Special Clinical Situations
NPO or Poor Oral Intake
Use a basal-plus-correction regimen (basal insulin with correction doses only) rather than scheduled prandial insulin. 1
Never completely withhold basal insulin, even when NPO, as it suppresses hepatic glucose production independent of food intake. 1
Glucocorticoid Therapy
Increase prandial and correction insulin by 40–60% in addition to basal insulin when patients are on high-dose glucocorticoids. 1
Example: If baseline prandial dose is 5 units per meal:
- Increase to 7–8 units per meal during steroid therapy
- Focus increases on lunch and dinner doses, as morning steroids cause afternoon/evening hyperglycemia 1
Continuous Tube Feeding
Use NPH insulin every 12 hours or regular insulin every 6 hours rather than rapid-acting analogs to cover continuous carbohydrate delivery. 1
Approximate insulin need at 1 unit per 10–15 grams of carbohydrate in the enteral formula. 1
Transition from IV to Subcutaneous Insulin
Give the first subcutaneous basal insulin dose 2–4 hours before stopping the IV insulin infusion to prevent rebound hyperglycemia and recurrent ketoacidosis. 1, 3
Calculate subcutaneous TDD as 60–80% of the 24-hour IV insulin infusion amount during stable control. 1, 3
Example: If a patient received 2 units/hour IV insulin (48 units/24 hours):
- Subcutaneous TDD = 48 × 0.7 = 34 units/day
- Basal: 17 units once daily
- Prandial: 17 units total → approximately 6 units before each meal
Common Pitfalls to Avoid
Do not use sliding-scale insulin as monotherapy—this reactive approach is condemned by all major diabetes guidelines and causes dangerous glucose fluctuations. 1
Do not delay adding prandial insulin when basal insulin exceeds 0.5 units/kg/day without achieving targets. 1
Do not continue escalating basal insulin beyond 0.5–1.0 units/kg/day without addressing postprandial hyperglycemia—this leads to over-basalization with increased hypoglycemia risk. 1
Do not rely solely on correction doses without adjusting scheduled basal and prandial insulin—correction doses must supplement, not replace, scheduled insulin. 1
Do not give rapid-acting insulin at bedtime as a sole correction dose—this markedly raises nocturnal hypoglycemia risk. 1
Expected Clinical Outcomes
With properly implemented basal-bolus therapy, approximately 68% of patients achieve mean glucose <140 mg/dL, compared with 38% using sliding-scale insulin alone. 1
Correctly executed basal-bolus regimens do not increase overall hypoglycemia incidence compared with inadequate sliding-scale approaches. 1
Target glucose range for non-critically ill hospitalized patients: 140–180 mg/dL 1
Practical Example: Complete Regimen for a 75 kg Patient
Scenario: 75 kg patient with type 2 diabetes, admission glucose 280 mg/dL, eating regular meals
Initial Orders:
- Basal insulin (glargine): 15 units subcutaneously once daily at bedtime (0.4 units/kg × 75 kg ÷ 2)
- Prandial insulin (lispro): 5 units subcutaneously before each meal (breakfast, lunch, dinner)
- Correction insulin (lispro): Add 2 units for pre-meal glucose >250 mg/dL; add 4 units for >350 mg/dL
- Glucose monitoring: Before each meal and at bedtime
Day 4 Adjustment (if fasting glucose 190 mg/dL and lunch postprandial glucose 220 mg/dL):
- Increase basal insulin to 19 units (4-unit increase for fasting ≥180 mg/dL)
- Increase lunch lispro to 6 units (1-unit increase for postprandial >180 mg/dL)
- Continue other doses unchanged
Day 7 Reassessment: Continue titration every 3 days until targets achieved