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Your blood glucose levels before pregnancy

Testing your blood glucose, and target levels

Having good blood glucose control before and during pregnancy will help to keep you and your baby healthy.

What testing system you will be offered

If you have type 1 diabetes:

  • You should be offered a continuous glucose monitor to test your blood glucose during pregnancy. This is a small device that you attach to your stomach. It checks your blood glucose throughout the day, and sends you alerts if your levels get too high or too low. You will still need to do some finger prick tests if you have continuous glucose monitoring.

  • You should be offered a flash glucose monitor as an alternative, if you have trouble using a continuous glucose monitor or if you prefer the flash monitor. Flash is a device that you attach to your arm, and it is similar to continuous glucose monitoring. The main differences are that it does not send you alerts when your blood glucose gets too high or too low, and that you have to scan the device to see what your current blood glucose level is.

If you do not have type 1 diabetes, you may still be offered continuous glucose monitoring if you are having trouble with blood glucose control (for example, if you are having lots of hypos).

If you are using continuous or flash glucose monitoring, your care team should show you how to use the system and provide support if you have any trouble with it. They should tell you how to get help outside of office hours if you need it.

If you are not offered continuous or flash glucose monitoring, you should be offered a monitor and testing strips. Your diabetes care team will give you advice about how often to test. If your medications are changed to try to lower your blood glucose level, you should test more often than usual.

Target blood glucose levels

Your care team should talk with you about how to control your blood glucose, and agree ideal (or target) levels with you that are manageable without causing hypoglycaemia. You should usually aim for the following levels:

  • between 5 mmol/litre and 7 mmol/litre before breakfast ('fasting' level)

  • between 4 mmol/litre and 7 mmol/litre before meals at other times of the day.

The targets might be different before you go to bed and if you need to test after meals.

HbA1c levels

Your care team should offer you an HbA1c test every month. This tells you your average blood glucose level over the last 2 to 3 months. You should usually aim for a target HbA1c of below 48 mmol/mol (or 6.5%) before you get pregnant, as long as this doesn't cause problems with hypoglycaemia. Even if getting your HbA1c to this level is not possible, any decrease towards the target will help reduce the risk of problems for your baby. If your HbA1c is very high (above 86 mmol/mol, or 10%), your care team should strongly advise you not to try for a baby until it has fallen, because of the increased risk of serious problems.

Ketone testing

If you have type 1 diabetes, your care team should give you testing strips and a monitor so that you can test your blood ketone levels if your blood glucose levels are too high (known as hyperglycaemia) or if you are unwell (for example, if you are vomiting or have diarrhoea). The strips are used to check for a serious condition that can affect people with diabetes, called diabetic ketoacidosis, or DKA for short.

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