Insulin Delivery

Overview

Insulin Delivery tracks the amount of insulin administered for diabetes management. This metric captures both basal (background) insulin that maintains glucose control between meals and bolus (mealtime) insulin that covers carbohydrate intake and corrects high blood glucose levels. Accurate insulin delivery data is fundamental to diabetes self-management and clinical decision-making.

How It's Measured

Insulin delivery is tracked through connected diabetes devices:

• Insulin pumps: Automatically log all programmed and delivered insulin with timestamps
• Smart insulin pens: Record dose amounts, timing, and pen temperature
• Manual logging: Patient-entered data for traditional pen or syringe injections
• Data includes:
  • Dose amount in international units (IU)
  • Delivery type (basal vs. bolus)
  • Timestamp of delivery
  • For pumps: programmed vs. actually delivered amounts
  • Extended/square wave bolus information

Health Significance

Insulin delivery data serves multiple critical purposes in diabetes care:

• Dose optimization: Enables fine-tuning of insulin regimens based on patterns
• Hypoglycemia investigation: Correlates low glucose events with preceding insulin doses
• Adherence assessment: Identifies missed doses or inconsistent timing
• Total daily dose trends: Tracks changes in insulin requirements over time
• Basal-bolus balance: Ensures appropriate distribution for glycemic control
• Time-in-range improvement: Data-driven adjustments to increase optimal glucose time

Clinical Interpretation Guidelines

When reviewing insulin delivery data for clinical decisions:

1. Total Daily Dose (TDD) analysis:
   • Calculate average TDD over 7-14 days for stable assessment
   • Significant changes in TDD may indicate illness, activity changes, or insulin resistance shifts
   • TDD >1.5 IU/kg suggests significant insulin resistance
2. Basal-bolus ratio:
   • Typical ratio: 40-50% basal, 50-60% bolus
   • High basal percentage may indicate insufficient bolus dosing or carb counting errors
   • High bolus percentage may suggest inadequate basal rates
3. Bolus timing assessment:
   • Pre-meal timing (15-20 minutes before) optimal for most rapid-acting insulins
   • Delayed bolusing contributes to postprandial hyperglycemia
4. Correction dose patterns:
   • Frequent correction boluses suggest basal or carb ratio inadequacy
   • Time of day patterns reveal specific adjustment opportunities
5. Pump-specific metrics:
   • Suspend time: Excessive suspension indicates overcorrection risk
   • Temporary basal use: Patterns around exercise or illness
   • Auto-mode percentage: Indicator of system compatibility
6. Smart pen insights:
   • Missed dose patterns: Identify problematic times or days
   • Dose consistency: Variations may indicate carb counting issues

Caveats & Limitations

• Programmed vs. delivered: Pump malfunctions may create discrepancies
• Injection site issues: Lipohypertrophy affects absorption, not captured in data
• Insulin type matters: Onset and duration vary by formulation
• Missing data: Injections with non-connected devices not automatically captured
• Does not equal absorption: Delivery confirmed does not guarantee proper absorption
• Context required: Data meaningless without corresponding glucose and carb information
• Device-specific limitations: Not all pumps/pens integrate with HealthKit
• Temperature sensitivity: Insulin degradation not reflected in delivery data

Additional Notes

For comprehensive diabetes management, insulin delivery data should be reviewed alongside continuous glucose monitoring (CGM) data, carbohydrate intake, and physical activity. The most valuable insights come from overlaying insulin doses with glucose response curves to identify timing and dosing opportunities. Automated insulin delivery (AID) systems provide the most complete picture, as they capture micro-adjustments that manual regimens cannot. When counseling patients, focus on patterns over individual doses and celebrate improvements in time-in-range rather than scrutinizing specific values.