Adjusting insulin

Objective: To adjust background insulin dose according to blood glucose levels

In a non-diabetic person, background insulin is produced throughout the whole days, as well as large pulses of insulin at the time of eating. We are trying to recreate this natural system for people with type 1 diabetes by using the basal bolus insulin regimen. This involves taking a long acting insulin (basal) as well as the rapid acting insulin (bolus) with each meal and with snacks.

The long acting insulin (e.g. glargine, detemir) should keep your blood glucose stable overnight and between meals. It is usually given once a day. It can be injected at any time of the day, but it is important to keep to a similar time of day each time you inject it.

How do you know if your background insulin dose is correct? The key is to look at your blood glucose monitoring. You must test your blood glucose before bed and before breakfast. If the background insulin dose is right for you, your blood glucose will stay controlled overnight and the reading before breakfast will be between 4 and 7 mmol/l. You also need to look at the bedtime reading. If the readings before bed and on waking are similar, this indicates the background insulin dose is correct.

If the before breakfast reading is above 7 mmol/l: you may not have had enough background insulin - you may need to increase the dose. But check your reading before bed. If this is also high, it may be that you just went to bed with a high reading and you actually need to increase your insulin dose with your evening meal / dinner.

If the before breakfast reading is below 4 mmol/l or if you had a night-time hypo: you may have had too much background insulin - you may need to reduce the dose.

Do not make any changes based on just one reading. Look for a pattern of similar events happening over 3 consecutive days. And only increase or decrease your background insulin dose by small amounts (2 to 4 units).

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Objective: To calculate and apply insulin correction doses

OK, so life's not perfect. Although we want you to give the correct dose of insulin to cover the carbohydrate in your food, things can go wrong. There might be an error in your calculation or there may just be other things going on upsetting your blood glucose.

If your blood glucose is higher than it should be before eating, you should give yourself additional insulin to correct this and bring is down to target - this is called the correction dose. This means that you give yourself the right amount of insulin to cover the carbohydrate in the food, but also give an extra dose to bring the blood glucose down to the pre-meal target (less than 7 mmol/l).

How do you work out your correction dose?

Start by calculating your total daily insulin dose (both rapid and long acting)

Divide this number into 100

THIS IS YOUR CORRECTION DOSE

You use this to get your pre-meal blood glucose down to 7 mmol/l

It tells you how much 1 unit of insulin will reduce your blood glucose by

Here's a calculation:

If your total daily insulin dose is 32 units (12 units rapid and 20 units long acting)

Divide this number into 100

This gives your correction dose = 3

You use this to get your pre-meal blood glucose down to 7 mmol/l

It tells you that 1 unit of insulin will reduce your blood glucose by 3 mmol/l

If your blood glucose is 10 mmol/l before lunch, you need to take an additional 1 unit of insulin with the food insulin to get the blood glucose down to 7 mmol/l.

But remember, this calculation is only the starting point. You may well need to adjust your correction dose. Some people need more insulin and some people need less. It is only by trying it out and testing your blood glucose that you will be able to tell if you have got it right.

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