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What should my blood glucose levels be?

Everybody is different, and everybody’s blood glucose management will be different, so it’s important to check with your Diabetes Healthcare Team about the levels you should aim for. But, there are general blood glucose ranges that you can use as guidelines.
Content last reviewed and updated: 13.03.2024

A woman with type 1 diabetes using a blood glucose meter

Medically, if you have type 1 diabetes there are targets for what your blood glucose levels should be, and we’ll explain the reasons for this. But remember that you’re human, not a robot, so don’t be hard on yourself if you don’t meet these targets all the time. There are many factors that affect blood glucose levels, many of which – like heat, cold, illness, or periods – are outside of your control.

What is time in range?

Time in Range (TIR) is the overall percentage of time that a person spends with their blood glucose levels within target range. TIR is calculated in real time, so you can check your TIR at any point based on the last 24 hours.

The target range varies from person to person, and you’ll need to speak to your Diabetes Healthcare Team about what your target percentage should be. In general, most people’s target range is between 3.9-10.0 mmml/L. Target percentages are based on things like age and how you take your insulin so they’re different for everyone.

How do you measure time in range?

To find out the percentage of time you’ve spent in range, you need to use a glucose sensor (either a continuous glucose monitor (CGM) or flash sensor).

If you use a CGM or flash sensor, your software will automatically calculate your percentage time in range.

Everyone in the UK with type 1 is entitled to sensor technology. Find out more about how this technology works and how to access it in our treatment and technology guide.

Find out more about TIR, including what it is, how to measure it and how to improve it if you need to.

What are the blood glucose targets for type 1 diabetes?

There are also target ranges for when you check your glucose levels at certain points of the day, for example before or after you eat.

Your Diabetes Healthcare Team will tell you what your personal target should be, but as a a general guide, the target range for normal blood glucose levels are:

  • Blood glucose levels before eating: 4-7 mmol/L
  • Blood glucose levels after eating (two hours after meals): 8-9 mmol/L
  • Blood glucose levels at bedtime: 6-10 mmol/L

You may need to consult your doctor and change your treatment plan if:

  • Blood glucose is consistently lower than 4 mmol/L or higher than 10 mmol/L before meals
  • Blood glucose is consistently lower than 6 mmol/L or higher than 12 mmol/L at bedtime

Blood glucose goals may be modified for children and others who are at greater risk of hypoglycaemia.

Are blood glucose targets different if you’re pregnant?

If you’re pregnant it is important to have tight management of your blood glucose levels. Find out more about type 1 and pregnancy.

How type 1 diabetes technology can help

There are some pieces of type 1 diabetes technology that can help improve the amount of time you spend within the ideal targets. Continuous glucose monitors give you real-time information about your blood glucose levels and data which you can review with your Diabetes Healthcare Team. There is also flash glucose monitoring, which gives you glucose data when you scan a sensor on your arm.

With both these devices you can set alarms to let you know if you’re going too high or too low, which can help you keep within your target range.

Reviewing data can help you identify trends and patterns in your levels and help you address them.

What happens if you spend too much time out of range?

Whilst you don’t have to be perfect, spending too much time out of range can cause health issues. Consistently high blood glucose levels can increase your risk of complications and low blood glucose levels can cause hypoglycaemia.

What is a dangerous level of blood glucose?

Very high blood glucose levels can be dangerous because, in extreme cases, it can lead to diabetic ketoacidosis which can be life-threatening.

Getting your Hba1c checked

When you have your regular diabetes check-up, you will also have your Hba1c levels reviewed by your Diabetes Healthcare Team. Find out more about Hba1c.

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