What is a blood glucose level (BGL)?

A BGL measures the concentration of glucose in the blood at the time of the check. Performing blood glucose levels, recording them in your record book, and reviewing them regularly is the only way you will know how to determine the correct dose of insulin to give. You need to know how to adjust insulin doses.

The target range for BGLs is 4.0mmol/L – 7.0mmol/L before main meals.

BGL record book

Blood glucose record book

BGL meter

When you come into hospital with a new diagnosis of diabetes, you will be given a glucose meter. It is a good idea to have a back up glucose meter at home just in case something happens to the main meter. 

You can purchase a meter from your local chemist. We suggest that your back up meter can check both glucose and ketone levels. 

Here is one online site that sells the Freestyle Optium Neo meter. This meter uses the same strips as the Freestyle Libre meter and checks for glucose and ketone levels.  

BGL’s need to be checked a minimum of four times a day

• Before breakfast
• Before lunch
• Before dinner
• Before supper
• Overnight 2–3 times a fortnight.

BGL’s may need to be tested at other times of the day

• If hypo is suspected
• If you feel unwell
• Before commencing sport or exercise
• Before driving a car

It can also be helpful to check BGLs

• 2-3 hours after meals
• Before recess/snack time

An assessment of blood glucose levels tell you if you are getting the correct dose of insulin. Growing children will require regular insulin dose adjustment.

• If the BGL’s are consistently less than 4.0mmol/L you are getting too much insulin and doses of insulin need to be decreased
• If the BGL’s are consistently above 7.0mmol/L before meals you are not getting enough insulin and doseses of insulin need to be increased

All BGL readings and insulin doses should be recorded in a record book. Keeping a detailed record of your BGL’s allows you to assess if you need to make changes to your insulin doses.

Always wash and dry hands before taking a BGL as food on your fingers can alter the BGL reading.

The ACCU-CHEK FastClix lancing device has been proven to be the least painful and overall easiest to use. This should have been provided for you to use at diagnosis. For video instructions on how to use the lancing device please

NOTE: the RCH advices that lancets should only be changed once a day not at each BGL test as per the video

How to do a blood glucose check

Managing BGLs, what to do;

• BGL less than 4.0 mmol/L (hypoglycaemia)
  A BGL of less than 4.0 mmol/L is a low blood sugar and needs to be treated
  Click here to learn about how to treat a low blood sugar
  It is important to record all the low BGLs in the record bookhis helps to identify a pattern in the BGLs. If there is a pattern of BGLs below 4 mmol/L at the same time of the day for 3-4 days in a row it means that insulin doses need to be decreased to help the BGL trend to be more between 4-7 mmol/L
  Mild hypoglycaemia is common and is an expected part of well controlled diabetes
  
  
• BGL between 4 - 7 mmol/L
  This is the target range and is showing that the right amount of insulin is working in the body
• BGLs between 7 - 15 mmol/L (out of range)
  A BGL between 7 - 15 mmol/L is higher than the target range. There is no immediate action if a BGL is in this range if your child is well. If your child is unwell click here. It is important to write down all the levels in your record book. This helps to identify a pattern in the BGLs. If there is a pattern of BGLs above 7 mmol/L at the same time of the day for 3-4 days in a row it means that an increase is needed in the insulin doses to help the BGL trend to be more between 4-7 mmol/L. Click here to learn about how to adjust insulin doses.
• BGL is 15 mmol/L or higher (hyperglycaemia)
  When a BGL is 15 mmol/L or higher it means that ketones need to be checked. Click here to learn about ketones. If ketones are negative (under 1.0 mmol/L) there is no immediate action needed. It is important to write down all the levels in your record book. This helps to identify a pattern in the BGLs. If there is a pattern of BGLs above 7 mmol/L at the same time of the day for 3-4 days in a row it means that an increase is needed in the insulin doses to help the BGL trend to be more between 4-7 mmol/L. Click here to learn about how to adjust insulin doses.