What is the recommended approach for managing blood glucose levels in a patient with diabetes using an insulin sliding scale?

Insulin Sliding Scale: An Outdated and Ineffective Approach

Sliding scale insulin (SSI) as monotherapy should not be used for hospitalized patients with diabetes, as it is associated with inferior glycemic control, increased complications, and dangerous glucose fluctuations compared to scheduled basal-bolus insulin regimens. 1, 2, 3

Why Sliding Scale Insulin Fails

SSI is a reactive approach that treats hyperglycemia only after it occurs, rather than preventing it. 3 This fundamental flaw leads to:

• Rapid blood glucose fluctuations that exacerbate both hyperglycemia and hypoglycemia 2, 3
• Poor glycemic control: Only 38% of patients on SSI achieve mean blood glucose <140 mg/dL, compared to 68% with basal-bolus regimens 2, 3
• Increased hospital complications, including postoperative wound infections and acute renal failure 2, 3
• Clinically significant hyperglycemia that persists throughout hospitalization 2

The VA/DoD guidelines explicitly state that SSI regimens "should be discouraged" because they do not produce favorable in-hospital outcomes compared to regimens using basal and preprandial insulin. 1

The Recommended Alternative: Basal-Bolus Insulin

For Hospitalized Patients with Good Oral Intake

Start with a scheduled basal-bolus regimen consisting of basal insulin, prandial insulin before meals, and correction doses as needed. 1, 2, 3

Initial dosing:

• For insulin-naive patients or those on low-dose insulin: Start with 0.3-0.5 units/kg/day total daily dose 2, 3
• Allocate 50% as basal insulin (given once daily) and 50% as rapid-acting prandial insulin (divided before meals) 2, 3
• For patients on high-dose home insulin (≥0.6 units/kg/day): Reduce total daily dose by 20% during hospitalization to prevent hypoglycemia 2, 3

Lower-risk dosing:

• For elderly patients (>65 years), those with renal failure, or poor oral intake: Use 0.1-0.25 units/kg/day 4, 2

For Patients with Poor or No Oral Intake

Use a basal-plus approach: basal insulin with correction doses of rapid-acting insulin only. 2, 3

• Start with 0.1-0.25 units/kg/day of basal insulin 2
• Add correction doses of rapid-acting insulin only when blood glucose exceeds 180 mg/dL 2
• Continue basal insulin coverage even with minimal intake, rather than relying solely on correction doses 4

Evidence Supporting Basal-Bolus Over Sliding Scale

Randomized controlled trials consistently demonstrate superiority of basal-bolus regimens:

• Better glycemic control: Basal insulin with preprandial correction doses and basal-bolus-plus-correction regimens both produced superior glycemic control compared to SSI alone 1
• Fewer treatment failures: Both basal-bolus approaches resulted in fewer treatment failures than SSI 1
• Reduced surgical complications: Basal-bolus insulin reduced risk for postsurgical complications 1
• Lower complication rates: Patients achieved better glucose control with reduced hospital complications including wound infections and acute renal failure 2, 3

A meta-analysis found that despite heterogeneity in results, the trend consistently favored basal-bolus regimens over SSI for clinical outcomes. 5

Limited Acceptable Uses of Sliding Scale Insulin

SSI might be acceptable only as an adjunct (not monotherapy) in these specific situations: 2

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

Even in these situations, SSI should be used as a temporary adjunct to scheduled basal insulin, not as monotherapy. 4, 2

Practical Implementation: Simplified Correction Doses

When correction insulin is needed as an adjunct to scheduled basal-bolus therapy, use a simplified approach: 4

• 2 units of rapid-acting insulin for premeal glucose >250 mg/dL 4, 2
• 4 units of rapid-acting insulin for premeal glucose >350 mg/dL 4, 2

If correction doses are frequently required, increase the scheduled basal or prandial insulin doses accordingly rather than continuing to rely on corrections. 2

Critical Safety Considerations

Hypoglycemia Risk

The basal-bolus approach carries a 4-6 times higher hypoglycemia risk than SSI alone (OR 5.75,95% CI 2.79-11.83 for blood glucose ≤70 mg/dL). 3

Mitigation strategies: 3

• Implement hospital-wide hypoglycemia protocols for glucose <70 mg/dL
• Review and adjust the treatment regimen after any glucose <70 mg/dL
• Use basal-plus (rather than full basal-bolus) for fasting patients or those undergoing procedures
• Reduce total daily insulin by 50% in patients with decreased oral intake

Monitoring Requirements

• Point-of-care glucose monitoring before each meal and at bedtime for patients eating regular meals 4
• Target glucose range: 140-180 mg/dL for non-critically ill hospitalized patients 4, 2
• For patients with poor oral intake: Check glucose every 4-6 hours 4

Common Pitfalls to Avoid

• Never use SSI as monotherapy for hospitalized patients with diabetes—this is explicitly condemned by all major diabetes guidelines 1, 2, 3
• Never administer rapid-acting insulin at bedtime—this increases risk of nocturnal hypoglycemia 4
• Avoid premixed insulin (70/30) in hospitals—it has unacceptably high hypoglycemia rates 4, 2
• Do not continue SSI regimens without modification even when control remains poor—this is a common error 2

Transitioning from IV to Subcutaneous Insulin

When discontinuing IV insulin infusion: 3

• Administer subcutaneous basal insulin 2-4 hours before stopping IV infusion 3
• Convert at 60-80% of daily IV infusion dose 3
• Calculate the daily dose based on the average insulin infused during the previous 12 hours 2