Correction Factor

The 1800 Rule For Determining Your Correction Factor

When your blood sugar goes unexpectedly high, a correction bolus can be used to bring it down. To use the right correction bolus, you first determine your correction factor. The 1500 Rule for Regular was originally developed by Paul Davidson, M.D. in Atlanta, Georgia. Because the blood sugar tends to drop faster and farther on Humalog and Novolog insulins, we modified the 1500 Rule to an 1800 Rule for these insulins. (Some use a 2000 rule for these insulins.) The 1800 Rule shows how far your blood sugar is likely to drop per unit of Humalog and Novolog insulin. The 1500 Rule shows how far it will drop per unit of Regular.

Numbers between 1600 and 2200 can be used to determine the correction factor. The number 1800 should work when the TDD is set correctly and the basal insulin makes up 50% of the TDD in someone with Type 1 diabetes. A number smaller than 1800 will work better when basal insulin doses make up less than 50% of the TDD, while a number higher than 1800 works better for those whose basal doses make up more than 50% of their TDD. Also, recheck your TDD and basal percentage to make sure they are correctly set.

Setting up your correction boluses can be done only after your basal doses have been tested for accuracy. If your basal doses are set too high, using a correction bolus may lead to lows, while basal doses that are too low will make it appear that correction boluses are not the right amount to bring high readings down as expected.

The 1800 Rule:

  • Works for Type 1 diabetes and most Type 2s
  • Estimates the point drop in mg/dl per unit of Humalog or Novolog
  • 1800/TDD = point drop per unit of Humalog (see Table)
  • Example:
    Someone’s Total Daily Dose of insulin = 30 units
    1800/30 u/day = a 60 point drop per unit of Humalog
  • The 1800 Rule allows you to set up an accurate personal Sliding Scale to lower unwanted highs!
The 2200 to 1600 Rules
2200 Rule 2000 Rule 1800 Rule 1600 Rule
Total Daily
Insulin Dose
Point Drop
per unit of
Hum. or Novolog
Point Drop
per unit of
Hum. or Novolog
Point Drop
per unit of
Hum. or Novolog
Point Drop
per unit of
Hum. or Novolog
20 110 mg/dl 100 mg/dl 90 mg/dl 80 mg/dl
25 88 mg/dl 80 mg/dl 72 mg/dl 64 mg/dl
30 73 mg/dl 67 mg/dl 60 mg/dl 53 mg/dl
35 63 mg/dl 57 mg/dl 51 mg/dl 46 mg/dl
40 55 mg/dl 50 mg/dl 45 mg/dl 40 mg/dl
50 44 mg/dl 40 mg/dl 36 mg/dl 32 mg/dl
60 37 mg/dl 33 mg/dl 30 mg/dl 27 mg/dl
75 29 mg/dl 27 mg/dl 24 mg/dl 21 mg/dl
100 22 mg/dl 20 mg/dl 18 mg/dl 16 mg/dl

Adapted from Using Insulin © 2003

Correction Dose Tips:

  • A properly set correction bolus allows you to bring down high blood sugars to within 30 mg/dl (1.7 mmol) of your target blood sugar after 5 hours with Novolog or Humalog insulins.
  • The mg/dl or mmol that your blood sugar drops per unit of insulin will generally be stable at breakfast, lunch, and dinner. If your correction factor varies at different times of the day, retest your basal doses to be sure they are correctly set.
  • Factors such as an extremely high blood sugar, ketoacidosis, infection, increased weight, or less activity can reduce how many points the blood sugar will drop per unit and cause more insulin to be needed to bring down a high blood sugar.
  • Loss of weight or increase in activity lowers your TDD and causes your blood sugar to fall farther per unit of insulin.
  • When an unexpected high blood sugar occurs, think about what may be causing it to rise. If illness, pain, or bad insulin is causing the problem, you may require a larger correction bolus.
  • If your high blood sugars often do not drop to your target, you may need a larger TDD and smaller correction factor.
  • If your high blood sugars frequently drop below your target, you may need a smaller TDD and larger correction factor. Recalculate your TDD and raise both your basal insulin and carb boluses appropriately. Use extra caution when correcting a high blood sugar near bedtime. Consider reducing the correction bolus to half its normal amount.

Pumping Insulin provides much more pump information and is the most helpful book ever written on insulin use.

Using Insulin takes you step-by-step toward excellent control. Whether you use one injection and pills, or six injections, you’ll learn far more from this book than from any other!