What is Sliding Scale Insulin?
Sliding scale insulin (SSI) is a reactive, outdated approach to insulin dosing that should NOT be used as monotherapy in hospitalized patients with established diabetes—it treats hyperglycemia after it occurs rather than preventing it, leading to dangerous glucose fluctuations and poor outcomes. 1, 2, 3
Definition and Mechanism
Sliding scale insulin is a method where short-acting or rapid-acting insulin is administered in increasing doses based on current blood glucose readings, typically using a predetermined table or "scale" 3. The insulin dose increases as blood glucose rises, hence the term "sliding scale" 4.
- SSI has been used for over 80 years without substantial evidence supporting its effectiveness as standard care 3
- The approach is purely reactive—it responds to hyperglycemia after it has already occurred rather than preventing it 2, 3
- SSI provides no basal insulin coverage, leaving patients without continuous background insulin between correction doses 2
Why SSI Fails as Monotherapy
The evidence overwhelmingly demonstrates that SSI alone is associated with poor glycemic control and worse outcomes:
- When used alone without standing intermediate-acting insulin, SSI is associated with a 3-fold higher risk of hyperglycemic episodes compared to no pharmacologic treatment at all (RR 2.85-3.25) 5
- SSI monotherapy provides no benefit over routine diabetes medications in preventing hyperglycemia (33.3% vs 34.6% hyperglycemia rates) or hypoglycemia 6
- Basal-bolus regimens reduce postoperative complications compared to SSI alone 2
- SSI is associated with clinically significant hyperglycemia and poor clinical outcomes including infections, prolonged hospital stay, poor wound healing, and higher morbidity 7, 2
Limited Appropriate Uses
SSI alone may be acceptable ONLY in these specific scenarios:
- Patients without pre-existing diabetes who develop mild stress hyperglycemia during hospitalization 1, 2
- Patients with well-controlled type 2 diabetes (HbA1c <7%) managed by diet alone at home who develop mild hyperglycemia during hospitalization 1, 2
SSI should NEVER be used as monotherapy for:
- Patients with type 1 diabetes 2
- Patients with type 2 diabetes on insulin at home 2
- Patients with established insulin requirements 2
Recommended Alternative: Basal-Plus or Basal-Bolus Regimens
For hospitalized patients requiring insulin, use scheduled basal insulin with correction doses, not SSI alone:
- Basal-plus regimen: Basal insulin 0.1-0.25 units/kg/day once daily PLUS correction doses of rapid-acting insulin before meals or every 6 hours if NPO 1
- Basal-bolus regimen: 50% of total daily dose as basal insulin (glargine or detemir) once or twice daily, 50% as prandial insulin (aspart, lispro, or glulisine) divided before meals, PLUS correction insulin as needed 2
For Your Specific Patient on Fiasp and Basalog
In the context of your patient managed with Fiasp (insulin aspart) and Basalog (insulin glargine):
- Fiasp is the rapid-acting prandial insulin covering meals and used for correction doses 8
- Basalog is the basal insulin providing 24-hour background coverage 8
- If someone mentions "sliding scale" for this patient, they likely mean using Fiasp for correction doses as part of a complete basal-bolus regimen—NOT as monotherapy 2
- The correction doses should be calculated using an insulin sensitivity factor (1500 ÷ total daily dose) to determine how much one unit of Fiasp lowers blood glucose 8
Critical Safety Considerations
- Basal-bolus regimens provide better glycemic control but carry 4-6 times higher risk of hypoglycemia compared to SSI alone (RR 5.75 for blood glucose ≤70 mg/dL) 1
- Every hospital must implement standardized hypoglycemia management protocols when using scheduled insulin regimens 2
- For patients on high-dose insulin at home (≥0.6 units/kg/day), reduce total daily dose by 20% during hospitalization to prevent hypoglycemia 1