In an adult patient who is critically ill in the intensive care unit, what is the recommended blood glucose target range and insulin infusion protocol, including adjustments for pre‑existing diabetes, high‑dose steroids, and short ICU stays with enteral nutrition?

Blood Glucose Management in Critically Ill ICU Patients

Initiation Threshold

Initiate insulin therapy when blood glucose persistently exceeds 180 mg/dL on two consecutive measurements in any critically ill adult patient, regardless of diabetes history or other factors. 1

• This threshold applies universally to all ICU populations including medical, surgical, cardiac, neurological, septic, and trauma patients 2
• The 180 mg/dL trigger is intentionally set lower than the target range to prevent prolonged exposure to harmful hyperglycemia 1
• Persistent hyperglycemia ≥180 mg/dL causes osmotic diuresis, endothelial glycocalyx dysfunction, immune impairment, and increased infection risk 1, 2

Target Blood Glucose Range

Maintain blood glucose between 140–180 mg/dL for all critically ill adults once insulin therapy is initiated. 1, 2, 3

• This recommendation is based on the landmark NICE-SUGAR trial, which demonstrated that intensive glucose control (80–110 mg/dL) increased mortality by 2.5% absolute risk and produced a 10–15-fold increase in severe hypoglycemia compared to the 140–180 mg/dL target 4, 3
• The 2024 Society of Critical Care Medicine guidelines provide a conditional recommendation with moderate certainty to avoid lower targets (80–139 mg/dL) specifically to reduce hypoglycemia risk 1

Exception for Highly Selected Patients

• A more stringent target of 110–140 mg/dL may be considered only for post-cardiac surgery patients if and only if this can be achieved without significant hypoglycemia 1, 4, 3
• Do not apply tighter targets to general ICU populations, as this increases mortality without benefit 2, 3

Insulin Delivery Method

Use continuous intravenous insulin infusion as the preferred route for all critically ill patients requiring glycemic control. 1, 2, 3

• The 2024 Society of Critical Care Medicine guidelines provide a conditional recommendation (very low certainty) favoring IV insulin over subcutaneous insulin in critically ill adults 1, 2
• IV insulin's short half-life (<15 minutes) permits rapid titration in response to fluctuating hemodynamics, nutrition, and insulin resistance 2, 3
• Never use subcutaneous insulin in hemodynamically unstable patients, during hypotension, or shock due to unpredictable absorption 2, 3

Standard Dosing Protocol

• Start continuous IV regular insulin at 0.1 units/kg/hour after confirming serum potassium >3.3 mEq/L 4, 2
• For severe hyperglycemia >300 mg/dL or diabetic ketoacidosis, consider an initial IV bolus of 0.15 units/kg before starting the infusion 4, 2
• For non-DKA hyperglycemia, a loading bolus is optional and not universally required 2

Monitoring Requirements

Monitor blood glucose every 1–2 hours during insulin infusion until values stabilize, then reduce to every 2 hours once stable. 1, 2, 3

• The 2024 Society of Critical Care Medicine guidelines recommend frequent monitoring at ≤1-hour intervals or continuous glucose monitoring when available during periods of glycemic instability 1, 2
• Monitor serum potassium closely, as insulin drives potassium intracellularly; maintain K+ >3.3 mEq/L before initiating insulin 4, 2

Protocol-Driven Care

Implement a validated insulin infusion protocol with explicit clinical decision support tools (computerized or paper-based) to guide titration. 1, 2

• The 2024 Society of Critical Care Medicine guidelines provide a conditional recommendation with moderate certainty for using protocols with explicit decision support tools over protocols without such tools 1
• Protocols must demonstrate low hypoglycemia rates in validation studies before implementation 1, 2
• Computerized decision support systems improve glycemic control and reduce hypoglycemia compared to protocols lacking explicit guidance 2, 3

Special Populations and Adjustments

Patients with Pre-existing Diabetes

• The same 180 mg/dL initiation threshold and 140–180 mg/dL target range apply regardless of diabetes history 1, 2
• Observational data suggest potential benefit from personalized targets matching chronic prehospital control (indicated by HbA1c), but this remains a research recommendation pending high-quality interventional trials 1

Patients on High-Dose Steroids

• Apply the standard 180 mg/dL threshold and 140–180 mg/dL target; steroid-induced hyperglycemia does not warrant different targets 1, 2
• Anticipate higher insulin requirements due to steroid-induced insulin resistance 2

Short ICU Stays with Enteral Nutrition

• Even for anticipated short ICU stays, initiate IV insulin at the 180 mg/dL threshold to prevent prolonged hyperglycemia 1, 2
• Continuous enteral feeding does not change the target range; maintain 140–180 mg/dL 4, 2
• When transitioning to subcutaneous insulin for step-down, administer basal insulin 1–2 hours before discontinuing the IV infusion to ensure adequate overlap 4

Critical Pitfalls to Avoid

• Never use sliding-scale insulin alone as the primary regimen; it causes unacceptable glycemic variability and increased complications 2, 3
• Do not target glucose <140 mg/dL in unselected critically ill patients; this increases mortality and severe hypoglycemia risk 4-fold without improving outcomes 1, 2, 3
• Do not delay insulin initiation when glucose exceeds 180 mg/dL; persistent hyperglycemia causes progressive harm through osmotic diuresis and immune dysfunction 1, 2
• Never discontinue IV insulin without prior subcutaneous dosing, especially in patients with type 1 diabetes or DKA, as this precipitates rapid metabolic decompensation 4

Hypoglycemia Management

Implement a hypoglycemia management protocol before starting insulin therapy and treat hypoglycemia (≤70 mg/dL) immediately without delay. 1, 2

• Even a single episode of mild hypoglycemia (<80 mg/dL) is associated with increased mortality and prolonged ICU length of stay 5
• Severe hypoglycemia (<40 mg/dL) dramatically increases mortality risk, especially with prolonged or repeated episodes 2, 3
• Use protocols that demonstrate low hypoglycemia rates in validation studies 1, 2