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Managing your child’s blood glucose levels

Learn about blood glucose levels, how they’re measured, what affects them, how to check them – and what you should do if they are too high or low.
Content last reviewed and updated: 15.08.2023

A dad taking his daughter's blood glucose levels via a finger prick test

What are blood glucose levels?

A blood glucose level is the amount of glucose (sugar) in your child’s blood. The amount of glucose goes up and down depending on many factors, mainly how much carbohydrate your child eats and how much glucose they burn off playing and running around.

Having type 1 diabetes means that your child’s body doesn’t make insulin, which is a hormone that makes sure the amount of glucose in the blood doesn’t go too high.

Because the body can’t do this, you have to monitor your child’s blood glucose levels and make adjustments, either by giving them something to eat to bring it up or injecting insulin to bring it down.

What are blood glucose levels measured in?

Blood glucose levels are measured in units called mmol/L (milli-moles-per-litre).

In the US, blood glucose levels are measured in mg/dl (milligrams per deciliter). If you read about blood glucose readings that seem very high, like 140 or 220, divide them by 18 to get the mmol/L.

What affects blood glucose levels?

Blood glucose levels are affected by many factors. Although eating carbohydrates and physical activity are the two main factors, glucose levels can also be affected by other things like growth spurts, heat, cold, illness or hormonal changes. That’s why it’s important to check them regularly.

How do I check my child’s blood glucose levels?

There are different ways of checking your child’s glucose levels, depending on what works best for them.

Your child can do a finger prick test with a blood glucose meter. A blood glucose meter measures glucose the blood itself (known as capillary blood), which gives the most accurate blood glucose reading.

Continuous glucose monitors (CGM) send constant readings of your child’s glucose levels to a handset or mobile phone. There is also flash glucose monitoring, where you scan a sensor attached to your child’s upper arm with a handset or mobile phone to take a reading.

CGM and flash measure interstitial fluid, which is the fluid between the blood vessels and cells. This is a good measure of glucose levels, but you’ll sometimes need to use a blood glucose meter to check your child’s capillary blood if the CGM or flash reading doesn’t match their symptoms.

Find out more by reading our treatments and technology pages.

What should my child’s blood glucose levels be?

Nobody expects you and your child to get perfect blood glucose levels all the time. There will be things that will affect their levels that neither of you can control, like heatwaves in summer or picking up an illness.

Your Diabetes Healthcare Team will give you targets specific to your child. As a general guide, the target range for 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

Find out more about target glucose levels.

What should you do if your child’s glucose levels are high or low?

In simple terms, if your child’s glucose level is low they need to eat some carbohydrate to bring it up. If their levels are high they will need to inject insulin to bring it down.

Learn more about managing high and low glucose levels on our hypers and hypos pages.

What is Time in Range?

Time in Range (TIR) is the overall percentage of time that someone with type 1 spends with their blood glucose levels within target range.

You can measure TIR if you’re using a continuous glucose monitor (CGM) or flash glucose sensing.

What is an HbA1c?

HbA1c is a measurement that shows what your child’s blood glucose level has been over a period of weeks or months, which makes it different from the glucose checks you do every day. This gives your Diabetes Healthcare Team a view of your child’s type 1 over a period of time. It is usually checked around three times a year.

Your Diabetes Healthcare Team will arrange for a blood test, usually before your child’s check-up, so that they can review your child’s HbA1c with you.

Find out more about HbA1c.

Explore other topics in this section

Read more

Managing your child’s hypos

Hypos can be dangerous – but the good news is they’re simple to treat and there is technology available to help you see when one is about to happen.

Read more

Managing your child’s hypers

Hypers don’t hold an immediate risk to your child’s health like hypos do, but they can make them feel unwell and can be serious if they’re not treated.

Read more

Carb counting for a child with type 1

Learn how to count carbs, understand the different types of carbs and how to guage how much insulin to take.

Read more

Working with your child’s healthcare team

Your child will be seen regularly by a team of diabetes specialists. Learn about the different professionals involved and how to best work with them.