Sliding Scale Insulin Should NOT Be Used
Sliding scale insulin (SSI) regimens should be discontinued for hospitalized non-critically ill adults with diabetes, as they provide no benefit in glycemic control and are associated with increased hyperglycemic events compared to basal-bolus insulin regimens. 1, 2
Why SSI Fails
The evidence against SSI is compelling and consistent:
Meta-analysis of 11 RCTs (1,322 patients) demonstrated that SSI resulted in significantly higher mean blood glucose levels (weighted mean difference +27.33 mg/dL) and increased incidence of hyperglycemic events compared to non-sliding-scale regimens, with no difference in severe hypoglycemia rates 1
Cochrane review (8 trials, 1,048 participants) found SSI resulted in mean blood glucose levels 14.8 mg/dL (0.8 mmol/L) higher than basal-bolus insulin (95% CI 7.8 to 21.8; p<0.001) 2
Prospective cohort study of 171 patients showed that when SSI was used alone, it was associated with a 3-fold higher risk of hyperglycemic episodes compared to no pharmacologic treatment (RR 2.85-3.25) 3
The Recommended Alternative: Basal-Bolus Insulin
Use a basal-bolus insulin regimen instead, which consists of:
- Basal insulin: Long-acting insulin analogue (e.g., glargine, detemir, degludec) given once or twice daily to provide background insulin coverage
- Bolus insulin: Rapid-acting insulin analogue (aspart, lispro, glulisine, or faster-acting insulin aspart) given before meals based on carbohydrate counting and premeal blood glucose 4
Key Implementation Points:
- Target glucose range: 5.6-10 mmol/L (100-180 mg/dL) for general ward patients, with consideration for higher targets in certain populations 5
- Dose calculation: Base bolus doses on carbohydrate intake, premeal blood glucose, and anticipated physical activity 4
- Correction doses: Can be added to meal-time bolus insulin (creating a "correction dose insulin" or CDI regimen), but this differs fundamentally from reactive SSI 6
Important Caveats
When Basal-Bolus May Increase Hypoglycemia Risk
The Cochrane review found that while basal-bolus insulin achieved better glycemic control, all 9 severe hypoglycemic episodes (blood glucose <40 mg/dL) occurred in the basal-bolus group (2.4% of 369 participants vs 0% in SSI group) 2. However, this risk must be weighed against the proven harm of persistent hyperglycemia.
Mitigation strategies:
- Ensure adequate patient education
- Monitor blood glucose frequently (at least before meals and bedtime)
- Adjust doses based on trends, not single values
- Consider higher glucose targets in patients at high risk for hypoglycemia (elderly, renal impairment, cognitive impairment)
Special Consideration for Bedtime Insulin
Recent evidence suggests that bedtime rapid-acting insulin is unnecessary for glucose levels <300 mg/dL (16.7 mmol/L). A quasi-experimental study found that eliminating bedtime SSI for glucose <300 mg/dL actually resulted in lower mean morning glucose levels (decrease of 16 mg/dL) 7.
Why SSI Persists Despite Evidence
Guidelines have advised against SSI for nearly 20 years 5, yet it remains widely used:
- 21% of nursing home residents were on SSI in week 2 of admission 6
- It's a "hallmark prescription for medical interns" despite being ineffective 5
The paradigm shift to basal-bolus insulin offers:
- Better patient outcomes
- Lower workload for healthcare providers 5
- More physiologic insulin delivery
Common Pitfall to Avoid
Do not confuse correction dose insulin (CDI) with traditional SSI. CDI involves giving variable correction doses alongside scheduled basal and bolus insulin, which is fundamentally different from reactive SSI alone. CDI is acceptable as part of a comprehensive basal-bolus regimen 6.