What is the effect of 1 unit of Novorapid (insulin aspart) on blood glucose levels, measured in mmol/L?

Insulin Sensitivity Factor for NovoRapid (Insulin Aspart)

The expected blood glucose reduction from 1 unit of NovoRapid (insulin aspart) typically ranges from 1.5-3.0 mmol/L, though this varies significantly based on individual insulin sensitivity, timing relative to meals, and baseline glucose levels.

General Insulin Sensitivity Estimates

While the provided guidelines do not specify exact glucose reduction per unit for NovoRapid, clinical practice and the evidence suggest:

• Individual variability is substantial - insulin sensitivity differs based on body weight, insulin resistance, time of day, and concurrent medications 1
• The "1500 rule" or "1800 rule" is commonly used in clinical practice to estimate insulin sensitivity factor (ISF), though these specific calculations are not detailed in the provided guidelines
• Correction doses in simplified regimens suggest that 2-4 units of rapid-acting insulin are used for glucose elevations of approximately 5.5-11 mmol/L above target, implying roughly 1.4-2.8 mmol/L reduction per unit 1

Context-Dependent Glucose Reduction

Postprandial vs. Correction Dosing:

• When used for meal coverage, NovoRapid's glucose-lowering effect is partially offset by food absorption, making direct per-unit calculations less applicable 2
• For correction doses (without concurrent food intake), the glucose reduction per unit is more predictable and typically falls in the 2-3 mmol/L range for insulin-sensitive individuals 1

Timing Considerations:

• NovoRapid demonstrates peak action within 1-3 hours of administration 3
• The glucose nadir (lowest point) typically occurs 3-4 hours post-injection when used without food 3
• Exercise timing significantly affects glucose reduction, with reductions of 3.8-4.7 mmol/L observed during 60-minute exercise sessions following NovoRapid administration 3

Clinical Application in Hospital Settings

Simplified Sliding Scale Recommendations: The American Diabetes Association guidelines for older adults suggest 1:

• For premeal glucose >13.9 mmol/L (250 mg/dL): give 2 units of rapid-acting insulin
• For premeal glucose >19.4 mmol/L (350 mg/dL): give 4 units of rapid-acting insulin

This implies an expected reduction of approximately 2.8 mmol/L per unit (5.5 mmol/L reduction from 2 units) in the higher glucose ranges.

Safety Considerations

Hypoglycemia Risk:

• Major hypoglycemic events occur in approximately 0.83 times the rate compared to regular human insulin, though this difference was not statistically significant 4
• Night-time hypoglycemia requiring parenteral treatment occurs less frequently with insulin aspart (1.3% vs 3.4% of patients) 4
• Post-exercise hypoglycemia is a particular concern, with ultra-rapid formulations showing reduced risk compared to standard aspart 3

Target Glucose Ranges:

• For hospitalized patients, target glucose of 7.8-10.0 mmol/L (140-180 mg/dL) is recommended 5
• Fasting goals of 5.0-8.3 mmol/L (90-150 mg/dL) are appropriate for stable patients 1

Practical Dosing Approach

Initial Correction Dose Calculation:

• Start conservatively with the assumption that 1 unit will reduce glucose by approximately 2.0 mmol/L in insulin-sensitive individuals
• Adjust based on observed response over 3-4 hours 1
• For insulin-resistant patients or those on higher total daily doses, expect smaller reductions per unit (potentially 1.0-1.5 mmol/L per unit)

Common Pitfalls:

• Stacking insulin doses within 3-4 hours increases hypoglycemia risk significantly 1
• Ignoring meal timing - NovoRapid given with food will have different net glucose effects than correction doses alone 2
• Overlooking exercise effects - physical activity can amplify insulin action by 3.8-4.7 mmol/L during the activity period 3