How does sliding scale insulin (SSI) work?

How Sliding Scale Insulin Works

Mechanism and Approach

Sliding scale insulin (SSI) is a reactive approach that administers rapid-acting or short-acting insulin based on current blood glucose readings, typically before meals or at scheduled intervals, with the dose increasing as blood glucose rises—but this method is strongly discouraged by all major guidelines as the sole regimen for hospitalized patients with diabetes. 1, 2

The Reactive Problem

• SSI treats hyperglycemia after it has already occurred rather than preventing it, leading to a cycle of blood glucose fluctuations between hyper- and hypoglycemia 2, 3
• The approach provides no basal insulin coverage, meaning patients have no background insulin to suppress hepatic glucose production or maintain stable glucose levels between meals 1, 2
• In practice, SSI regimens are often continued throughout hospitalization without modification, even when glucose control remains persistently poor 2, 4

Clinical Evidence Against SSI Alone

• Meta-analysis of 11 randomized controlled trials (1,322 patients) showed SSI resulted in significantly higher mean blood glucose levels (weighted mean difference = 27.33 mg/dL) and increased hyperglycemic events compared to basal-bolus regimens 5
• Only 12% of SSI injections successfully reduced elevated glucose to target range (90-130 mg/dL), while 84% of injections were subtherapeutic with glucose remaining elevated 4
• Randomized trials consistently demonstrate that basal-bolus regimens achieve target glucose control in 68% of patients versus only 38% with SSI alone 2, 3

When SSI Might Be Acceptable (Limited Circumstances)

• Patients with mild stress hyperglycemia without pre-existing diabetes 2
• Patients with well-controlled diabetes (HbA1c <7%) on minimal home therapy who have mild hyperglycemia during hospitalization 1
• Patients who are NPO with no nutritional replacement and only mild hyperglycemia 1
• Patients who are new to steroids or tapering steroids 1

The Preferred Alternative: Basal-Plus or Basal-Bolus

All major guidelines (American Diabetes Association, Endocrine Society, Diabetes Canada, Australian Diabetes Society) recommend scheduled insulin regimens with basal insulin as the foundation, using correction doses of rapid-acting insulin for hyperglycemia rather than SSI alone. 1, 2

For patients with good oral intake:

• Start with basal-bolus regimen: 0.3-0.5 units/kg total daily dose, divided 50% basal (once daily) and 50% prandial (before meals) 1, 2, 3
• Add correction doses using a sliding scale on top of scheduled insulin 1, 2

For patients with poor oral intake or NPO:

• Use basal-plus approach: 0.1-0.25 units/kg/day of basal insulin plus correction doses of rapid-acting insulin for hyperglycemia 6, 3
• This provides background insulin coverage while allowing flexibility for unpredictable nutrition 6, 3

Common Pitfalls to Avoid

• Never use SSI alone for type 1 diabetes—this is dangerous as these patients require basal insulin to prevent diabetic ketoacidosis 2, 3
• Avoid continuing the same SSI regimen without adjustment when glucose control remains poor—if correction doses are frequently needed, increase scheduled insulin doses accordingly 2, 3
• Do not use premixed insulin (70/30) in hospitals due to unacceptably high hypoglycemia rates 1, 3
• For patients on high insulin doses at home (≥0.6 units/kg/day), reduce total daily dose by 20% during hospitalization to prevent hypoglycemia 2, 3

Documentation and Monitoring Challenges

• Studies reveal that approximately 30% of anticipated care points involving SSI had missing information about execution, timing, glucose levels, or insulin doses 4
• This documentation failure compounds the ineffectiveness of SSI and makes dose adjustments nearly impossible 4

Bottom Line

Sliding scale insulin works by giving increasing doses of rapid-acting insulin in response to elevated glucose readings, but this reactive approach is ineffective and potentially harmful when used alone. The evidence overwhelmingly supports using scheduled basal insulin with correction doses rather than SSI as a sole regimen. 1, 2, 5