Adjusting insulin

Objective: To be able to adjust insulin doses according to food and blood glucose
 
On the Windfal course, you learnt about adjusting your insulin dose according to the carbohydrate content of food and your blood glucose level (measured before meals and before bed and before breakfast).
 
This is complicated. People can forget what to do and perhaps they lose the motivation to apply this system day to day.
 
So these pages are to remind you of the principles of adjusting your insulin dose. There are three sections given below. You can just click through to them. When you have read through anything you feel rusty about, why not try the 'Quiz'!

1. How to work out your insulin to carbohydrate (CP) ratio

Objective: To adjust rapid acting insulin doses according to meal carbohydrate

After eating, your blood glucose rises as the food is digested and absorbed into your body. In non-diabetic people, insulin is released from their islet cells to control their blood glucose levels. In people with type 1 diabetes, these cells have been damaged and you have to inject insulin to control your blood glucose level.

The increase in blood glucose comes from digesting carbohydrate. So if you know how much carbohydrate is in your food, you can give yourself enough insulin to control your blood glucose level. However, different people need different amounts of insulin per portion of carbohydrate. People come in different shapes and sizes and some people are still producing small amounts of insulin of their own.

Start with: 1 unit of insulin per CP

CP is a carbohydrate portion = 10g of carbohydrate

Usual requirements: Between and 3 units of insulin per CP

Most people start with using 1 unit of rapid acting insulin (e.g. novorapid, humalog) for every CP they eat. This may need to be increased or decreased. You may need to take more or less insulin per CP at different times of the day. So you have to work out what's right for you!

How do you know if your insulin to carbohydrate ratio is correct? The key is to look at your blood glucose monitoring. You must test your blood glucose before each meal. If you have taken enough insulin with a meal, this will control your blood glucose levels and the reading you get before your next meal will be between 4 and 7 mmol/l. 
  • If you have taken enough insulin with breakfast, your blood glucose before lunch will be between 4 - 7 mmol/l.
  • If you have taken enough insulin with lunch, your blood glucose reading before dinner will be between 4 - 7 mmol/l.
  • If you have taken enough insulin with dinner, your blood glucose reading before bed will be between 4 - 7 mmol/l.
If the reading is above 7 mmol/l: you did not have enough insulin - you need to increase the amount of insulin per CP.

If the reading is below 4 mmol/l or if you have a hypo between meals: you had too much insulin - you need to reduce the amount of insulin per CP.

Do not make any changes based on just one reading. Look for a pattern of similar events happening over 2 or 3 days. And only make one change at a time or it gets too confusing.

Click here if you would like to see an example. Click here if you're ready for the 'Quiz'!

Click here if you would like to go back to 'Adjusting insulin'.

2. How to work out if your background insulin dose is right for you

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).

Click here if you would like to see an example. Click here if you're ready for the 'Quiz'!

Click here if you would like to go back to 'Adjusting insulin'.

3. How to work out and apply insulin correction doses

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.

Click here if you would like to see another example. Click here if you're ready for the 'Quiz'!

Click here if you would like to go back to 'Adjusting insulin'.

Working on it!