Basal Insulin Testing

Core Concepts

• Basal insulin testing is done to verify that your blood sugar is steady when nothing except your basal insulin affects your blood sugar
• Always verify your basal insulin dose before working on correction boluses or meal boluses
• The easiest way to verify your basal insulin dose is to look at your blood sugar when fasting; if it’s flat, your dose is set accurately 
• Make at least 2 fasting tests to verify your trend before making changes to your basal insulin
• Always make at least 2 fasting tests to confirm the effect of your change

Instructions for Testing

1. To avoid fasting for a full 24 hours, you can simply skip breakfast, lunch and dinner on different days
2. Make sure you are feeling well and have a stable blood sugar
3. Log your meals and insulin doses in the Carbon Health Diabetes Program app during the day of testing
4. Your last meal before fasting should be low in fat to prevent a delayed rise in BG
5. Avoid snacking, insulin corrections, and exercise. Water is OK, but avoid caffeine and alcohol
6. Start evaluating 4–5 hrs after your last meal
7. You should start with BG between 100 and 150 mg/dL. Stop basal testing and treat if BG < 70 mg/dL or > 250 mg/dL
8. Evaluate for at least 5 hours; a change of ≥30 mg/dL during this period suggests an adjustment is needed.

Overnight test

1. Start fasting after an early dinner at 6 PM
2. Start evaluating at 10 PM
3. End the test by having breakfast at 7 AM the morning after

Morning Test

1. Start fasting after a late dinner, no later than 11 PM
2. Start evaluating around 4 AM
3. End the test by having lunch around 12 PM

Afternoon Test

1. Start fasting after breakfast, no later than 8 AM
2. Start evaluating at 12 PM
3. End the test by having dinner later than 5 PM

Evening test

1. Start fasting after lunch, no later than 1 PM
2. Start evaluating at 5 PM
3. End the test by having late dinner no earlier than 10 PM

Sample Basal Testing Schedules