What is the target blood glucose range for inpatients to avoid hypoglycemia and how do different types of insulin, such as rapid-acting (e.g. lispro, aspart), short-acting (e.g. regular insulin), intermediate-acting (e.g. NPH insulin), and long-acting (e.g. glargine, detemir) insulins, work according to the American Diabetes Association (ADA) guidelines?

Inpatient Blood Glucose Targets and Insulin Pharmacology

ADA-Recommended Blood Glucose Targets to Avoid Hypoglycemia

For critically ill patients, the American Diabetes Association recommends maintaining blood glucose between 140-180 mg/dL (7.8-10.0 mmol/L) once insulin therapy is initiated, with insulin started when glucose persistently exceeds 180 mg/dL. 1, 2

For noncritically ill hospitalized patients, premeal glucose targets should be <140 mg/dL (7.8 mmol/L) with random blood glucose <180 mg/dL (10.0 mmol/L), provided these can be safely achieved. 1, 2

Critical Hypoglycemia Prevention Thresholds

• Reassess the insulin regimen immediately when blood glucose falls below 100 mg/dL, as this predicts hypoglycemia within 24 hours. 2

• Modify the regimen when blood glucose drops below 70 mg/dL, unless easily explained by missed meals. 2

• Hypoglycemia is formally defined as any blood glucose <70 mg/dL (3.9 mmol/L). 3

Target Refinements by Clinical Context

• More stringent targets of 110-140 mg/dL may be considered for select patients (such as post-cardiac surgery) only if achievable without significant hypoglycemia. 1

• Avoid glucose targets <110 mg/dL as they increase hypoglycemia risk and mortality without improving outcomes. 4

• Elderly hospitalized patients require particular caution, as they have impaired counterregulatory responses and often fail to perceive hypoglycemic symptoms. 1

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How Different Insulin Types Work

Rapid-Acting Insulins (Lispro, Aspart, Glulisine)

• Onset of action: 10-15 minutes after subcutaneous injection. 5

• Peak effect: 1-2 hours. 5

• Duration: 3-5 hours. 5

• Clinical use: Administered immediately before meals (or immediately after in young children) to cover prandial glucose excursions. 5

• Lispro was shown in clinical trials to achieve comparable glycemic control to regular insulin when used with basal insulin (NPH or glargine), with similar rates of severe hypoglycemia (1-2% in type 2 diabetes, 8-10% in pediatric type 1 diabetes on pump therapy). 5

Short-Acting Insulin (Regular Human Insulin)

• Onset of action: 30-60 minutes after subcutaneous injection.

• Peak effect: 2-4 hours.

• Duration: 6-8 hours.

• Clinical use: Must be administered 30-45 minutes before meals, making it less convenient than rapid-acting analogs. 5

• Regular insulin is the preferred formulation for intravenous continuous insulin infusion in critically ill patients due to its short half-life (<15 minutes IV), allowing rapid dose titration. 1

Intermediate-Acting Insulin (NPH)

• Onset of action: 1-2 hours after subcutaneous injection.

• Peak effect: 4-8 hours.

• Duration: 12-18 hours.

• Clinical use: Administered once or twice daily as basal insulin, though its pronounced peak increases hypoglycemia risk compared to long-acting analogs.

• NPH was used as the basal insulin comparator in multiple trials, showing similar efficacy but higher rates of severe hypoglycemia compared to long-acting analogs like glargine. 6

Long-Acting Insulins (Glargine, Detemir)

• Onset of action: 1-2 hours after subcutaneous injection. 6

• Peak effect: Relatively peakless profile (glargine has minimal peak). 6

• Duration: 20-24 hours (glargine), 12-24 hours (detemir, dose-dependent). 6

• Clinical use: Administered once or twice daily to provide steady basal insulin coverage, preferred over NPH due to lower hypoglycemia risk. 6

• In a 5-year study of type 2 diabetes patients, glargine showed comparable efficacy to NPH but with lower rates of severe symptomatic hypoglycemia (7.8% vs 11.9%). 6

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Recommended Insulin Regimens for Hospitalized Patients

Noncritically Ill Patients with Good Nutritional Intake

• The basal-bolus regimen is preferred, consisting of scheduled basal insulin (glargine or detemir) plus rapid-acting prandial insulin before meals and correction doses. 1, 2

• For insulin-naive patients, start with 0.3-0.5 units/kg total daily dose, with half as basal and half divided before meals. 2

• Lower doses (0.1-0.25 units/kg) are appropriate for patients at high hypoglycemia risk, including elderly (>65 years), renal failure, or poor oral intake. 2

Noncritically Ill Patients with Poor Oral Intake or NPO

• Basal-plus correction insulin is recommended, using long-acting basal insulin with correction doses only, avoiding prandial insulin. 1, 2

• For patients with mild hyperglycemia (blood glucose <200 mg/dL), this approach reduces hypoglycemia risk compared to full basal-bolus. 2

Critically Ill Patients

• Continuous intravenous insulin infusion is required, using regular insulin at 0.1 units/kg/hour (typically 5-7 units/hour in adults) after an initial bolus of 0.15 units/kg. 4

• Target glucose decline of 50-75 mg/dL per hour; if glucose does not fall by 50 mg/dL in the first hour, verify adequate hydration then double the infusion rate hourly. 4

• Use validated computerized or written protocols for insulin infusion adjustments to minimize hypoglycemia risk. 1, 4

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Critical Pitfalls to Avoid

• The sole use of sliding-scale insulin (SSI) in the inpatient setting is strongly discouraged by the ADA, as it is associated with poor outcomes and excludes basal insulin. 1, 4

• Never stop IV insulin abruptly—ensure 1-2 hour overlap with subcutaneous basal insulin to prevent rebound hyperglycemia. 4

• When transitioning from IV to subcutaneous insulin, calculate basal insulin dose as 60-80% of total daily IV insulin dose, or use half of the 24-hour IV insulin total as long-acting basal insulin. 4

• Each hospital should adopt and implement a hypoglycemia management protocol, with episodes documented in the medical record and tracked. 1