Treating High Blood Glucose with Injections or Insulin Pump
When your child’s blood glucose is elevated, extra rapid-acting insulin treating high blood glucose should be given to bring it back to the target range.
To do this, your child’s diabetes health care team may have assigned ONE of the following:
- Insulin Sensitivity Factor (ISF)
- Correction Number
- Correction Formula, or
- Sliding Scale
These are four different approaches with the same goal: correcting high blood glucose.
1. Insulin Sensitivity Factor
The Insulin Sensitivity Factor (ISF) indicates how sensitive an individual’s body is to insulin; it tells you how many points (in mmol/L) blood glucose drops when 1 unit of rapid-acting insulin is delivered.
For example, an ISF of 3 means one unit of insulin would drop blood glucose by 3 mmol/L (such as from 12.0 to 9.0); an ISF of 15 means one unit of insulin would drop blood glucose by 15 mmol/L (such as from 20.0 to 5.0).
ISF varies from person to person, based on a number of factors including: body size, body composition, age, and activity level. In general, smaller people are more insulin sensitive than bigger people; those with a lean body composition are more insulin sensitive than those with a higher percentage of body fat; younger children are more insulin sensitive than older children; and more active people are more insulin sensitive than less active people.
An individual person’s insulin sensitivity is affected by:
- Weight changes (gain or loss)
- Growth (both the change in size as well as the release of growth hormones)
- Change in physical activity levels (ex. sensitivity decreases when hockey season ends and your child’s activity level decreases)
- Prolonged periods of inactivity (ex. illness, sitting for long periods of travel)
- Change in seasons (sensitivity increases in spring)
- Stress (stress hormones decrease insulin sensitivity)
- Menstrual cycle
Your child’s ISF will need to change over time as he grows (which may be indicated by an increase in his Total Daily Dose of insulin) and as marked changes in any of the above factors occur.
The concept of ISF is used by an insulin pump to calculate a correction bolus. For those using injections, Insulin Sensitivity Factor (ISF) can be used to calculate how many units of insulin are needed to treat a high blood glucose, either by applying the finger-counting technique presented in (2) below, or by plugging the ISF into a Correction Formula shown in (3) below.
2. Correction Number
A Correction Number is based on ISF. The number provides you with a method for counting how many points (mmol/L) blood glucose will drop when 1 unit of rapid-acting insulin is delivered.
For example, a correction number of “4” means 1 unit of rapid-acting insulin will lower blood glucose 4 points. If the blood glucose is 18 and you give 1 extra unit of rapid-acting insulin, it will lower it to 14; 2 extra will lower it to 10; and 3 extra will lower it to the target blood glucose of 6.
An easy way to use the Correction Number to calculate how many units of insulin are needed to treat high blood glucose is to hold up a finger for every unit of insulin you “count out”. Using the example above: 18 minus 4 is 14 (hold up 1 finger for that first unit of insulin needed); 14 minus 4 is 10 (hold up a second finger) – is 10.0 your target blood glucose? If so, stop here and give 2 units of insulin (for the 2 fingers you are holding up). If not, continue subtracting where you left off: 10 minus 4 is 6 (hold up another finger, three in total now) – is 6.0 where you want to end up? If so, give 3 units of insulin (for the 3 fingers you are holding up.) If you want to end up at a blood glucose of 8.0, which is half way between 6 and 10, you would give 2.5 units of insulin, a dose halfway between 2 and 3 “fingers.”
3. Correction Formula
A correction formula uses ISF to compare the current blood glucose reading to a target blood glucose reading as follows:
Correction dose (in Units of insulin) = (Current BG) – (Target BG)
That is, the amount of insulin that should be delivered to correct an out-of-range blood glucose reading is calculated by: finding the difference between the current BG and the desired BG, and then dividing that difference by an individual’s ISF.
If blood glucose is higher than the target, you will add a correction bolus of insulin to bring blood glucose down, closer to the target.
If blood glucose is lower than the target, you will take away some insulin from a carb bolus to bring blood glucose up, closer to the target.
Example A: If your child’s current blood glucose reading is 15.0, his target blood glucose is 8.0, and his ISF is 10.0, the number of units of insulin he should be given to correct this high BG is 0.7 units:
15.0 – 8.0 = 0.70
Example B: If your child’s current blood glucose reading is 5.0, his target blood glucose is 8.0, and his ISF is 10.0, the number of units of insulin that should be taken away from his carb bolus to correct this lower-than-target BG is 0.3 units:
5.0 – 8.0 = -0.30U
If your child uses an insulin pump, these calculations will be made by the pump’s bolus calculator. Correction boluses can be delivered via a pump in increments as small as 0.05U.
If your child receives his insulin via injections, after using the above formula to calculate the correction bolus required, doses may be rounded to the nearest 1/2 unit. For Example A above, this would be 0.5U, and for Example B, negative .5U.
(Note: If you are using diluted insulin for injections, doses may be rounded to the nearest 1/4 unit, which would be .75U for Example A, and negative .25U for Example B).
Helpful Hint: If your child’s target blood glucose is expressed as a range (rather than a single number), aim for the centre of the target range. For example, if your child’s target range is 7.0 to 10.0 mmol/L, use 8.5 as your target BG in calculating blood glucose corrections.
4. Sliding Scale
Instead of providing a Correction Number, ISF, or Correction Formula as outlined above, your child’s doctor may provide you with a Sliding Scale. A Sliding Scale is a chart specifying how much insulin to give for a certain range of high blood glucose readings. A Sliding Scales is the result of the calculations outlined above, so no calculations are needed in order to use the Sliding Scale.
A sample sliding scale may look like this example (for a target of 6-12 mmol/L):
- If blood glucose is 12-15: give 0.5 units of insulin
- If blood glucose is 16-20: give 1.0 units of insulin
- If blood glucose is over 20: give 1.5 units of insulin
Note! These numbers are an example ONLY! Your child’s individualized sliding scale will be different.
A sliding scale recommends the same insulin dose for a range of blood glucose readings. That is, in the example above, 0.5 units of insulin would be given for a BG of 12.0, as well as a BG of 15.9. Sliding Scales are used most commonly for those on injections, as the calculation of a correction dose of .8U (for a BG of 16.0), and the correction dose of 1.2U (for a BG of 20.0) would both be rounded to the same number, 1.0U. So the sliding scale specifies for a BG of 16.0 or a BG of 20.0 and for everything in between, give 1.0U of insulin.
If you feel your child’s Correction Formula, Correction Number, Insulin Sensitivity Factor (ISF), or Sliding Scale is not working to correct high blood glucose to the target range (at least 50% of the time), these numbers may need to change to better reflect your child’s insulin needs.
For more information, consult your child’s diabetes health team or…
The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.
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