Information for the public

Checking your own blood glucose, and target levels

Having high blood glucose makes you more likely to get other health problems, so keeping your glucose levels as close to normal as possible is very important. Your diabetes care team will help you with this.

You will need to test your blood glucose every day, to make sure it does not get too high or too low – this is called self‑monitoring.

If you are pregnant, when you need to test and your target levels may be different from those given below – see the NICE guidance on diabetes in pregnancy.

How to check

It's best to monitor your blood glucose all the time using continuous glucose monitoring (CGM). You can choose between real-time continuous glucose monitoring (rtCGM) and intermittent-scanning continuous blood glucose monitor (isCGM, also called 'flash'). You and your diabetes team should choose a device together, based on your preferences and needs.

If you do not want or cannot use CGM, you can monitor your blood glucose level using a simple finger prick test with a home-testing kit.

Your diabetes care team should make sure you have all the equipment you need. They should also teach you how to use the device or kit and act on the results.

Finger prick testing: how often to test

You should test your blood glucose at least 4 times a day – before each meal and before you go to bed. You might need to test more often, such as before and during driving, when you exercise, if you start to feel unwell, during illness (as part of sick-day rules) or if you have problems with hypos.

Target blood glucose levels

Blood glucose levels are given in a unit of measurement that is written as 'mmol/litre' or 'mmol/l'.

To minimise your risk of long‑term problems caused by blood glucose levels that are higher than normal, you should aim for the following target levels:

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

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

If you have to test after a meal, the target level at least 90 minutes after eating is between 5 and 9 mmol/litre.

Your diabetes care team should talk with you about your blood glucose targets. This includes what level to aim for before you go to bed, which will depend on when you last ate and your insulin dose.

Questions to ask about testing your blood glucose

  • What are my target blood glucose levels?

  • How do I adjust my insulin dose to meet the targets?

  • Do all of my results need to be in the target range?

  • What can I do if I'm often missing my targets?

Questions to ask about finger-prick testing

  • Why do I need to test my blood glucose?

  • When should I test?

  • Is it OK to test after a meal rather than before?

  • When might I have to test more often?

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