At what blood glucose level do I start sliding scale insulin?

When to Start Sliding Scale Insulin

You should not start sliding scale insulin as a standalone regimen—it is strongly discouraged and ineffective for glycemic control in hospitalized patients. 1

The Evidence Against Sliding Scale Insulin Monotherapy

Multiple major diabetes organizations explicitly recommend against using sliding scale insulin (SSI) alone:

• The American Diabetes Association strongly discourages the sole use of SSI in the inpatient hospital setting. 1
• A 2025 systematic review of clinical practice guidelines found consensus across 10 major guidelines (ADA, Endocrine Society, Diabetes Canada, International Diabetes Foundation, and others) that sliding scale insulin should be avoided. 1
• SSI is a "reactive" approach that treats hyperglycemia after it occurs rather than preventing it, leading to poor glycemic control and rapid glucose fluctuations. 1

What You Should Use Instead

For hospitalized patients requiring insulin, use a basal-bolus regimen with scheduled insulin covering both basal and nutritional needs, plus correction doses. 1

The Preferred Approach:

• Basal insulin (glargine, detemir, degludec, or NPH) provides background coverage 1
• Prandial insulin (rapid-acting analogs: lispro, aspart, or glulisine) covers meals 1
• Correction insulin supplements when glucose exceeds targets 1

Evidence Supporting Basal-Bolus Over SSI:

• A randomized trial showed 68% of patients achieved glycemic control (mean glucose <140 mg/dL) with basal-bolus insulin versus only 38% with SSI alone, with no difference in hypoglycemia rates. 1
• Meta-analysis of 11 RCTs (1,322 patients) found SSI provided no benefits in glucose control but was associated with significantly higher mean glucose levels and more hyperglycemic events. 2

The Only Acceptable Use of Sliding Scale

Sliding scale correction doses may be used as an adjunct to scheduled basal-bolus insulin, not as monotherapy. 1, 3

When Adjusting Prandial Insulin in Older Adults:

The American Diabetes Association provides this simplified approach while titrating scheduled insulin 1, 3:

• For premeal glucose >250 mg/dL (>13.9 mmol/L): Give 2 units of rapid-acting insulin 1, 3
• For premeal glucose >350 mg/dL (>19.4 mmol/L): Give 4 units of rapid-acting insulin 1, 3
• Stop the sliding scale when not needed daily 1, 3

Critical Safety Points:

• Never use rapid-acting insulin at bedtime due to nocturnal hypoglycemia risk 1, 3
• Target premeal glucose of 90-150 mg/dL (5.0-8.3 mmol/L) in most patients 1, 3
• If correction doses are frequently required, increase the scheduled insulin doses rather than continuing to rely on sliding scale 1

Special Circumstances Where SSI Might Be Acceptable

The Society of Hospital Medicine identifies limited scenarios where SSI alone may be reasonable 1:

• Patients with HbA1c <7% (53 mmol/mol) on diet or low-dose oral agents only
• Patients with mild hyperglycemia who are NPO with no nutritional replacement
• Patients newly started on or tapering off corticosteroids
• Patients at high risk for hypoglycemia (end-stage liver/kidney disease, elderly, unknown drug overdose)

Common Pitfalls to Avoid

• The traditional practice of ordering SSI on admission and leaving it unchanged throughout hospitalization leads to persistent poor control 1
• SSI prescribed on admission is rarely modified even when control remains inadequate 1
• Documentation and monitoring deficiencies are common with SSI—one study found uncertainties or missing information in 30% of anticipated care points 4
• Only 6% of patients achieved good glycemic control through 5 days of SSI therapy in observational studies 4

Bottom Line

Do not start sliding scale insulin as your primary glycemic management strategy. Use scheduled basal-bolus insulin instead, with correction doses as a supplement only. 1 The evidence consistently demonstrates that SSI monotherapy is ineffective and should be discontinued in hospitals. 2