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 ½ 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 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.
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