Correction Doses

What is a correction dose?

A correction dose is the amount of extra short-acting insulin you need to take if your blood glucose is too high. Everybody’s dose is different and over time, you will get a feel for how much extra insulin to take as a correction dose.

Paul’s pre-lunchtime blood glucose reading is 14 mmol/L. He takes 2 extra units of insulin to bring his glucose level down to 8 mmol/L.

If you are just about to eat you can add your correction dose into your calculated mealtime insulin dose. You may also take a correction dose at other times when glucose is high (e.g. during illness), but should avoid taking a correction dose within 2-3 hours of your last short-acting insulin dose, as there is a risk of a low glucose event (hypo).

Insulin sensitivity factor (ISF)

The amount of insulin that you need to reduce blood glucose varies a lot from person to person, but on average 1 unit of insulin will reduce glucose by around 3 mmol/L. Your insulin sensitivity factor is a measure of how much 1 unit of insulin will reduce your blood glucose level by:

If 1 unit of insulin drops your blood glucose by 3 mmol/L then your insulin sensitivity factor is 1:3

If 1 unit of insulin drops your blood glucose by 5 mmol/L then your insulin sensitivity factor is 1:5

Calculating your starting correction dose/ISF

For most people, a good starting point is an ISF of 1:3. But if you want to calculate a starting ISF more accurately, then follow the steps below:

Calculate your average total units of injected insulin over 24 hours. You can do this by combining your total bolus insulin injections and your basal insulin injections over a 24-hour period. Then add these two values together for your total daily dose (TDD).

Total dose over a 24 hour period (on average of bolus insulin plus total dose over a 24 hour period (on average) of basal insulin = your total daily dose

The 100 Rule

Divide 100 by your total daily dose i.e. 100 ÷ TDD. This means that 1 unit of insulin will reduce your blood glucose by approximately X mmol/L.

100 divided by TDD = 'X' mmol/L of blood glucose will be reduced per single unit of insulin

For example, if the total daily insulin dose (TDD) is 30 units:

This means that 1 unit of insulin will reduce your blood glucose by approximately 3 mmol/L (you can round up or down to the nearest unit) and your ISF is 1:3.

Always check your ISF calculations with a health care professional before using them and be aware that your ISF may change over time. By regular glucose monitoring, you can work out if your ISF is correct and make small adjustments to it if needed.

To download a pdf guide on correction doses please click here.

Insulin pumps

If you use an insulin pump then you should consult your healthcare team and/or review advice on the insulin pump e-learning course as the ISF calculations may be slightly different e.g. 130 ÷ TDD is often used to calculate a starting ISF.

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