When to use a fixed dose versus an insulin sliding scale for glucose management?

Fixed Dose vs Insulin Sliding Scale for Glucose Management

Scheduled basal-bolus insulin regimens should be used instead of sliding scale insulin alone for hospitalized patients with diabetes, as sliding scale monotherapy is strongly discouraged and associated with inferior glycemic control and increased complications. 1, 2

Why Sliding Scale Insulin Alone Fails

Sliding scale insulin (SSI) is a reactive approach that treats hyperglycemia after it occurs rather than preventing it, leading to:

• Rapid blood glucose fluctuations that worsen both hyperglycemia and hypoglycemia 2
• Clinically significant hyperglycemia throughout hospitalization 2
• Poor glycemic control with only 38% of patients achieving mean blood glucose <140 mg/dL compared to 68% with basal-bolus regimens 2
• Increased hospital complications including postoperative wound infections and acute renal failure 1, 2

The fundamental problem: SSI regimens are often continued unchanged throughout hospital stays despite persistent poor control 2

When to Use Each Approach

Use Basal-Bolus Insulin (Fixed Dose) For:

• All patients with type 1 diabetes (mandatory - they require scheduled basal insulin) 1
• Hospitalized patients with type 2 diabetes and good oral intake - basal, prandial, and correction components 1
• Patients with poor or no oral intake - basal insulin or basal-plus correction regimen 1
• General surgery patients with type 2 diabetes - randomized trials show improved outcomes versus SSI 1

Sliding Scale Insulin Alone May Be Acceptable For:

• Patients without diabetes who have mild stress hyperglycemia 2
• Patients with well-controlled type 2 diabetes on oral agents at home who cannot maintain glucose <180 mg/dL (10.0 mmol/L) - though basal insulin may still be needed 1

Recommended Fixed-Dose Approach

Initial Dosing:

• Insulin-naive patients or low-dose users: Start 0.3-0.5 units/kg/day total daily dose 2

  • Allocate 50% to basal insulin
  • Allocate 50% to rapid-acting prandial insulin 2

• Patients on higher home insulin doses (≥0.6 units/kg/day): Reduce total daily dose by 20% during hospitalization to prevent hypoglycemia 1

• Elderly or high-risk patients: Use lower end of dosing range (renal failure, older age) 2

For Patients with Poor Oral Intake:

Use basal-plus approach rather than full basal-bolus 1:

• Single dose basal insulin: 0.1-0.25 units/kg/day 1
• Correction doses of rapid-acting insulin before meals or every 6 hours if NPO 1

This approach reduces hypoglycemia risk in patients with mild hyperglycemia (blood glucose <200 mg/dL) or decreased oral intake 1

Critical Safety Considerations

Hypoglycemia Risk:

The basal-bolus approach carries 4-6 times higher hypoglycemia risk than SSI alone 1:

• Blood glucose ≤70 mg/dL: Risk ratio 5.75 (95% CI 2.79-11.83) 1
• Blood glucose ≤60 mg/dL: Risk ratio 4.21 (95% CI 1.61-11.02) 1
• Incidence of mild hypoglycemia: 12-30% in controlled settings 1

To mitigate hypoglycemia:

• Implement hospital-wide hypoglycemia protocols for glucose <70 mg/dL 1
• Review treatment regimen after any glucose <70 mg/dL 1
• For fasting patients or those undergoing procedures, use basal-plus rather than full basal-bolus 1

What NOT to Do:

• Never use premixed insulin (70/30) in hospital - unacceptably high hypoglycemia rates 1
• Never use SSI as sole prolonged treatment - strongly discouraged 1
• Never administer prandial insulin before confirming oral intake - give immediately after meals with dose adjusted to intake 1

Transitioning from IV to Subcutaneous Insulin

When discontinuing IV insulin infusion 1:

• Administer subcutaneous basal insulin 2-4 hours before stopping IV infusion
• Convert at 60-80% of daily IV infusion dose 1

Special Populations

Older Adults:

Consider simplified regimens 1:

• Once-daily basal insulin may be reasonable option 1
• Use simplified sliding scale only as adjunct: 2 units for premeal glucose >250 mg/dL, 4 units for >350 mg/dL 1
• Stop sliding scale when not needed daily 1

Critical Care Setting:

• Use continuous IV insulin infusion with validated protocols 1
• This is the most effective method for achieving glycemic targets in ICU 1

Bottom Line Algorithm

1. Patient has type 1 diabetes? → Basal-bolus mandatory 1
2. Patient has type 2 diabetes with good oral intake? → Basal-bolus regimen 1
3. Patient NPO or poor intake? → Basal-plus approach 1
4. Patient has mild stress hyperglycemia without diabetes? → SSI alone may be acceptable 2
5. Never use SSI alone as prolonged sole therapy in patients with established diabetes 1