How to Use This Calculator
Step 1: Find Your Total Daily Insulin
Add Up Your Basal Insulin
This is your long-acting insulin (like Lantus or Levemir)
Add Your Bolus Insulin
This is insulin you take with meals
Add Them Together
Example: 20 units basal + 15 units bolus = 35 total units
Step 2: Choose Your Correction Insulin
Rapid-Acting Insulin
Humalog, Novolog, Apidra, or Fiasp - works in 15 minutes
Regular Insulin
Humulin R or Novolin R - works in 30-60 minutes
Get Your ISF Result
See how much one unit of insulin drops your blood sugar
How the Calculator Works
The Math Behind It
For Rapid-Acting Insulin
We use the 1800 Rule: 1800 ÷ your total daily insulin
For Regular Insulin
We use the 1500 Rule: 1500 ÷ your total daily insulin
Get Your ISF Number
This tells you how much 1 unit drops your blood sugar
Real Example
Sarah's Situation
Sarah takes 30 units of insulin total per day
The Calculation
1800 ÷ 30 = 60 mg/dL per unit
What It Means
Each unit of insulin drops Sarah's blood sugar by 60 mg/dL
The Formulas
ISF = 1800 ÷ Total Daily Insulin
For rapid-acting insulin
ISF = 1500 ÷ Total Daily Insulin
For regular insulin
Understanding ISF
What is ISF?
ISF (Insulin Sensitivity Factor) is also called your "correction factor." It tells you how much one unit of insulin will lower your blood sugar.
Why It Matters:
- • Helps you correct high blood sugar safely
- • Prevents taking too much or too little insulin
- • Keeps you from going low (hypoglycemia)
How to Use Your ISF
When your blood sugar is high, use your ISF to figure out how much insulin you need to bring it back to your target.
Quick Example:
- • Your blood sugar is 200 mg/dL
- • Your target is 100 mg/dL
- • Difference: 100 mg/dL
- • ISF is 50 → Take 2 units (100 ÷ 50 = 2)
Risk Factors
Things that can affect how sensitive you are to insulin
Things That Increase Sensitivity
These make insulin work BETTER (you need less):
- Exercise and physical activity
- Losing weight if overweight
- Getting enough sleep
Things That Decrease Sensitivity
These make insulin work LESS (you need more):
- Being sick or having an infection
- Stress or not sleeping well
- Hormones (like during periods or growth spurts)
Lifestyle Changes
Better Blood Sugar Control
Check Blood Sugar Regularly
Test before meals and 2 hours after to see how insulin is working
Keep a Diabetes Log
Write down blood sugar, insulin doses, and how you feel
Time Your Insulin Right
Rapid-acting: 15 min before eating. Regular: 30 min before
Healthy Habits
Stay Active
Exercise makes insulin work better, but check blood sugar first!
Eat Regular Meals
Don't skip meals - it makes blood sugar harder to control
Drink Water
Staying hydrated helps your body process glucose better
How to Get Accurate Readings
Testing Your ISF
- Test when blood sugar is high and you haven't eaten for 4+ hours
- Give a correction dose based on your calculated ISF
- Wait 3-4 hours and check blood sugar again
- See if you reached your target - adjust ISF if needed
Important Tips
- Wash hands before testing (food on fingers affects results!)
- Check meter and strips aren't expired
- Don't correct if you took insulin in the last 3 hours
- Your ISF might change over time - recheck every few months
When to Seek Emergency Care
Get help right away if you have these symptoms:
Severe Low Blood Sugar (Hypoglycemia):
- Can't think clearly or feeling confused
- Shaking badly or having seizures
- Can't wake up or pass out
- Blood sugar below 55 mg/dL and not rising
Severe High Blood Sugar (DKA - Diabetic Ketoacidosis):
- Throwing up and can't keep fluids down
- Breathing really fast or having trouble breathing
- Fruity smell on breath
- Blood sugar over 300 mg/dL with ketones
Call Your Doctor Soon If:
- Blood sugar stays high even with correction doses
- You're getting low blood sugar a lot
- Your ISF doesn't seem to be working right