Blood Glucose Testing


How useful is self-monitoring of blood glucose? When and how should it be used? This booklet provides some answers to enable you to manage your blood glucose levels more appropriately. Lots of people with diabetes carefully record blood glucose results then do nothing with them.

A healthcare professional should teach you when and how to test, and what to do with the results. Without knowing this, there is little point in self-testing. If you are unsure of what to do discuss this with your healthcare professional.

Diabetes and blood glucose levels  

The body regulates blood glucose (sugar) levels by controlling the amount of insulin it produces. In diabetes blood glucose levels rise above normal.

There are two main types of diabetes:

Type 1 diabetes: When the body produces little or no insulin. People who have this type of diabetes need injected insulin treatment for the rest of their lives.

Type 2 diabetes: When the body does not make enough insulin or cannot use insulin properly. This type of diabetes is often linked with obesity. It can sometimes be managed by lifestyle changes (diet and exercise) alone but often requires treatment with tablets, progressing to insulin eventually if blood glucose is not adequately controlled.

In diabetes, to prevent long-term health probelms it is important to carefully manage both blood glucose and cardiovascular risk factors (e.g. not smoking, controlling blood pressure and cholesterol).

This booklet explains blood glucose testing for the different types of diabetes.

When should I test more frequently

The following situations could indicate the need for more frequent blood glucose testing:

  • Pregnancy
  • Hypoglycaemia
  • Hyperglycaemia
  • Stress
  • Changes to your medication (tablets or insulin)
  • Changing the amount of exercise you take.

Your healthcare professional will advise you how often you should self-test if any of the above apply.

If you are ill (even minor illness like colds or flu) you should test at least four times a day.

When and where to seek help  

Contact your healthcare professional if the majority of
your blood glucose levels remain above 11 mmol/l without explanation or if you have unexplained low blood glucose levels. Do not worry if you have the odd level which is higher or lower than normal.

Please do not stockpile testing strips. Self-monitoring of blood glucose costs the NHS more than £100 million each year. Only request as many as you need and try to minimise waste due to strips passing their ‘use by’ date.

Always show records of your blood glucose to your healthcare professional.

If you do not inject insulin you should test your blood glucose 2-3 times a week, at different times of the day.

There is usually no benefit in testing more often than has been recommended by your healthcare professional, particularly if the majority of your blood glucose levels are within the normal range (between 4 – 7mmol/l before meals).

Diabetes managed using a sulphonylurea medicine

These medicines can cause hypoglycaemia so it is important to eat regular meals containing carbohydrate. Examples of sulphonylurea medicines include:

  • chlorpropamide
  • glimepiride
  • glibenclamide
  • gliquidone
  • gliclazide
  • tolbutamide
  • glipizide

Prandial glucose regulators can also cause hypoglycaemia. Examples include:

  • repaglinide
  • nateglinide

 How is long-term control of blood glucose monitored?

It is monitored using measurements of HbA1c (Which is blood haemoglobin that has glucose attached to it). The amount of HbA1c in the blood relates to the average amount of glucose that has been in the blood over the previous 6-12 weeks.

So if your blood glucose has been high during this time, your HbA1c result will be relatively high, too. Your HbA1c should be checked 3-4 times a year depending on how well your diabetes is controlled. Ideally you should aim to achieve an HbA1c of less than 7%. Ensure you keep a note of the results so you can track your progress.

What should my blood glucose levels be?  

Blood glucose levels are measured in millimoles per litre (mmol/l).

Ideally these should be:

  • Before meals, 4 – 7mmol/l
  • Two hours after meals, less than 9mmol/l

It is recommended that people with diabetes aim for blood glucose levels as close to normal as possible.

What affects my blood glucose levels?    

Type and quantity of carbohydrate (starchy and sugary) foods and drinks

  • Activity levels and exercise
  • Alcohol
  • Illness
  • Stress
  • Warm weather

High blood glucose levels – HYPERglycaemia

A high blood glucose level (more than 11mmol/l) is known as hyperglycaemia. Examples of when it may occur include: when you are ill, if you have eaten too much carbohydrate, or taken too little exercise.

Low blood glucose levels – Hypoglycaemia    

A low blood glucose level (usually less than 4mmol/l) is known as hypoglycaemia. Examples of when it may occur include: taking your tablets or insulin but not eating enough carbohydrate, or following vigorous exercise.

Should I test my blood glucose?  

If you inject insulin, you should test your blood glucose levels everyday. See the section on page 5 for information on how often and when.

If you have well-controlled type 2 diabetes which is treated with diet or tablets alone, you may not need to test your blood glucose as frequently. Discuss this with your doctor or diabetes specialist nurse.

If blood glucose monitoring is not acceptable to you then urine testing may be used. However, this will usually only show blood sugar levels when they are above 10mmol/l.

Urine testing may be preferred by some people with type 2 diabetes when it is controlled by diet, physical activity and metformin.

Learning how to test and what to do with the results  

A healthcare professional should teach you when and how to test. They will help you to interpret the results and make adjustments to your treatment if needed.

If you test you must keep a record of your glucose levels and show this to your healthcare professional at every visit. This way your results can be monitored and, if necessary, changes can be made to your medication, diet or lifestyle.

How often should I test?    

If you inject insulin you should test more frequently than if you manage your diabetes with tablets or through diet and exercise.

  • Newly diagnosed diabetics should test twice daily at different times of day. This will help you to build up a profile of what is normal for you. You may then wish to discuss the frequency of testing with your healthcare professional.
  • If you are using Dose Adjustment For Normal Eating (DAFNE) or are able to adjust your insulin dose you should test:
  •       – before each injection
  •       – at bedtime
  •       – occasionally two hours after a meal.
  • You should always test your blood glucose level before driving and every 2 hours during a long drive.
  • If you have type 1 diabetes and your blood glucose level shows as above 13.3mmol/l, you should also test your urine for ketones.


Diabetes UK Careline

  • telephone: 0845 120 2960 (9am – 5pm, Mon – Fri)

NHS Direct

  • 0845 46 47 (24 hours)

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s