What is the proper protocol for a patient with diabetes to use sliding scale insulin (SSI) therapy?

Sliding Scale Insulin Should Be Strongly Avoided as Monotherapy

Sliding scale insulin (SSI) alone is explicitly condemned by the American Diabetes Association and should not be used as the primary insulin strategy for hospitalized patients with diabetes. 1

Why SSI Fails as Monotherapy

SSI is a reactive approach that treats hyperglycemia after it occurs rather than preventing it, leading to dangerous glucose fluctuations and poor outcomes 2, 3. The evidence is clear:

• Only 38% of patients on SSI alone achieve adequate glycemic control (mean blood glucose <140 mg/dL) compared to 68% with scheduled basal-bolus regimens 2, 3
• SSI monotherapy is associated with increased hospital complications including postoperative wound infections and acute renal failure 2, 3
• SSI regimens often continue throughout hospitalization without modification, even when control remains poor 2

The Correct Approach: Scheduled Insulin Regimens

For Patients with Good Oral Intake

Use a basal-bolus regimen with three components: 1

1. Basal insulin (long-acting): Provides 24-hour background coverage
2. Prandial insulin (rapid-acting): Given before meals to cover food intake
3. Correction insulin: Supplemental doses for hyperglycemia (this is the only appropriate use of "sliding scale" dosing)

Initial dosing algorithm: 2, 3

• Start with 0.3-0.5 units/kg/day total daily dose
• Give 50% as basal insulin (once daily)
• Give 50% as prandial insulin (divided before three meals)
• Add correction doses using a simplified scale: 2 units for glucose >250 mg/dL, 4 units for glucose >350 mg/dL 2

For Patients with Poor Oral Intake or NPO Status

Use a basal-plus approach: 1, 2

• Give 0.1-0.25 units/kg/day as basal insulin
• Add correction doses of rapid-acting insulin only when glucose exceeds 180 mg/dL
• Never rely on correction insulin alone 1, 2

Limited Acceptable Uses of SSI

SSI might be appropriate only in these specific situations: 2

• Patients with mild stress hyperglycemia without pre-existing diabetes
• Patients with well-controlled diabetes (HbA1c <7%) on minimal home therapy who develop only mild hyperglycemia during hospitalization
• Patients who are NPO with no nutritional replacement and only mild hyperglycemia
• Patients who are new to steroids or tapering steroids

Critical Safety Considerations

The basal-bolus approach carries higher hypoglycemia risk than SSI alone (risk ratio 5.75), but this is manageable with proper protocols: 3

• Implement hospital-wide hypoglycemia protocols for glucose <70 mg/dL
• Review and adjust the regimen after any glucose <70 mg/dL
• Use lower starting doses (0.1-0.25 units/kg/day) for high-risk patients: elderly (>65 years), renal failure, or poor oral intake 2, 3
• Reduce home insulin doses by 20% during hospitalization for patients on ≥0.6 units/kg/day 2, 3

Titration and Monitoring

Adjust basal insulin every 3 days based on fasting glucose patterns: 1

• Target fasting glucose: 80-130 mg/dL
• Increase by 2 units if fasting glucose is 140-179 mg/dL
• Increase by 4 units if fasting glucose is ≥180 mg/dL

Adjust prandial insulin based on 2-hour postprandial glucose: 1

• Target postprandial glucose: <180 mg/dL
• Increase by 1-2 units every 3 days if consistently elevated

Common Pitfalls to Avoid

• Never use SSI as monotherapy for patients with type 1 diabetes 2, 3
• Never give rapid-acting insulin at bedtime as this significantly increases nocturnal hypoglycemia risk 1, 2
• Never use premixed insulin (70/30) in hospitals due to unacceptably high hypoglycemia rates 2
• Never abruptly discontinue oral medications (especially metformin) when starting insulin 4, 5

Transitioning from IV to Subcutaneous Insulin

When discontinuing IV insulin infusion: 3

• Administer subcutaneous basal insulin 2-4 hours before stopping IV infusion
• Convert at 60-80% of the daily IV infusion dose
• Calculate based on average insulin infused during the previous 12 hours