1/2 of the insulin is given as the basal rate and the other 1/2 is divided
into three premeal boluses. [1, 2]
The calculator below will help you to
estimate the initial insulin requirements.
Basal Rate
The basal rate is adjusted after evaluating blood
glucose levels throughout a 24-hour period.
Blood glucose levels are obtained:
- Before meals
- One hour post-prandial
- At bedtime
- 12:00 A.M.
- 3:00 A.M.
If adjustments to the basal rate are required, the
overnight basal rate is adjusted first. The basal rate is adjusted by 0.1 to 0.2 U/hr increments to keep the premeal and overnight blood glucose levels to within 30 mg/dl (1.7mmol/L) of the desired glucose range [2]
. Some patients have decreased basal insulin requirements between the hours of
12 AM and 3 AM and will need to have the basal rate decreased during those
hours. Patients who experience Dawn phenomenon
(resistance to insulin due to increased growth
hormone levels usually occurring ~ 5 AM) will need an increased basal rate
during the early morning hours.
Example basal rate settings for a patient with
Dawn phenomenon.
| Begin Time | Basal Rate |
| 12:00 AM | 0.6 U/hour |
| 4:00 AM | 0.8 U/hour |
| 10:00 AM | 1.0 U/hour |
Pre-meal Boluses
Boluses are adjusted according to postmeal blood glucose. The
pre-breakfast bolus will usually be ~ 8 units. Pre-lunch and pre-dinner
boluses are usually ~ 4 units. Correction of the bolus may be
needed if the premeal blood sugar is unacceptably high or low.
Covering
Carbohydrate
- The amount of insulin required
to cover a particular carbohydrate intake (Insulin/Carb ratio) may be estimated
from the "450 or 500 Rule":
- 450/total insulin dose=grams of carbohydrate
covered by 1 unit of insulin [4]
The
Insulin/Carb ratio may also be calculated using the patient's history. The
calculator below will help you to approximate the insulin required to cover a
given carbohydrate intake using the patient's total carbohydrate intake.
Correction Bolus
- The amount of insulin
necessary to correct an elevated premeal sugar may be estimated by the "1500
rule" (for regular insulin) or the "1800 rule" (for Humalog).
-
For a patient on regular insulin the 1500 rule
states that:
1500 divided by total daily insulin dose =
mg/dl that 1 unit of insulin will lower the blood glucose.
Premeal Insulin Bolus Calculation Using
Correction Bolus (using "1500 or 1800 Rules") and Carbohydrate Content of Meal
(using "450 or 500 Rules"):
References:
1.MiniMed Technologies: The Insulin Pump Therapy Book Insights From The Experts.
Hollywood, FL, MiniMed Technologies, 1998
2. Fredrickson L, Rubin RR, Rubin S. Optimal
pumping: a guide to good health with diabetes. Northridge, Calif: MiniMed, 2001:14-20
3. Walsh J
and Roberts R, Pumping Insulin by Published by Torrey Pines Press, 2000
4. Walsh J, Roberts R, Lois Jovanovic-Peterson
L, Stop the Rollercoaster: How to Take Charge of Your Blood Sugars in Diabetes Torrey Pines Press, 1996.
More information on the insulin pump is available
at:
