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Blood glucose monitoring

This page explains what blood glucose testing is and why it is required for people with diabetes. It covers what the numbers mean, how to control your blood glucose level and how and when to test your blood.

Contents

Blood glucose testing

Blood glucose control is very important for people with diabetes.

Checking your blood glucose regularly (using fingerprick testing) shows you how lifestyle changes affect your blood glucose levels and helps you maintain control of your diabetes. People with diabetes have an increased risk of a number of health issues such as heart, kidney and eye diseases, nerve damage, stroke and poor circulation.

Normal blood glucose ranges for people without diabetes are 3.5–5.5 mmol/L (millimoles per litre) before meals and less than 8 mmol/L two hours after meals. Foe people with diabetes, the closer the blood glucose is to normal, the better.

Self-monitoring (through home fingerprick testing) is most appropriate for:

  • patients with type 1 diabetes
  • patients with type 2 diabetes who use insulin regimes and adjust their dose as a result of blood glucose testing
  • patients who are pregnant, whether they have type 1, type 2 or gestational diabetes

Many people with type 2 diabetes, especially those who manage their diabetes through diet or who are on metformin or a glitazone, do not need to check their own blood glucose, as there is no risk of hypoglycaemia (low blood glucose). However, glucose monitoring might be useful in order to see the impact of lifestyle (food, drink and exercise) as well as the impact of any changes to medication.

For patients with type 2 diabetes who are taking a sulphonylurea (i.e. gliclazide, glimepiride, glipizide), a prandial glucose regulator (nateglinide or repaglinide), an incretin mimetic (exenatide, liriglutide or lixisenatide) or a medication ending with -gliptin, regular testing is not normally necessary. You may, however, need to be tested in particular circumstances, for example as an educational tool, if you have a recurrent illness or to ensure that you are safe to drive. If you suffer frequently from hypoglycaemia, your blood glucose should be monitored. Contact your diabetes care team for advice on home blood glucose meters.

Blood glucose target levels

Blood glucose is usually checked using fingerprick testing. Blood glucose targets are individual to each person, and you should agree target levels with your diabetes care team. The target blood glucose ranges in Table 1 below (from national guidelines) are indicated as a guide only.

Table 1: Target blood glucose ranges

  Waking Before meals Two hours after meals

Children: type 1 diabetes*

4–7 mmol/L  4–7 mmol/L 5–9 mmol/L

Adults: type 1 diabetes*

5–7 mmol/L 4–7 mmol/L 5–9 mmol/L
Type 2 diabetes** N/A  4–7 mmol/L less than 8.5mmol/L

Pregnant women with diabetes*

less than 5.3 mmol/L  less than 5.3 mmol/L

less than 7.8 mmol/L (one hour after eating)

less than 6.4 mmol/L (two hours after eating)

* National Institute of Clinical Excellence (NICE) 2015

** Diabetes UK Council of Health Care Professionals 2015

HbA1c

When you have a diabetes check-up, a blood sample is taken for the HbA1c (haemoglobin A1c) test. This lets you know what your average blood glucose has been over the previous three months. Target ranges (from national guidelines) are shown in Table 2 below. Evidence shows that if you can achieve these levels, you will minimise the risk of long-term vascular complications.

Table 2: Target HbA1c ranges

  Target HbA1c Considerations

Adults: type 1

diabetes*

48 mmol/mol (6.5%) or lower You should agree an individualised HbA1c target with your diabetes care team, taking into account factors such as daily activities, likelihood of complications, occupation and history of hypoglycaemia.

Adults: type 2 diabetes* (managed either by lifestyle and diet, or by lifestyle and diet combined with a single drug not associated with hypoglycaemia)

 

48 mmol/mol (6.5%) or lower Your HbA1c targets should be reviewed on an individual basis. Your diabetes care team may decide to set a more relaxed target level if they feel that intensive management would not be appropriate in your case.

Adults: type 2 diabetes* (managed with a drug associated with hypoglycaemia, e.g. insulin or gliclazide)

53 mmol/mol (7.0%) or lower

 

Why test my blood glucose?

Blood testing is the best way to stay in control of your diabetes because it tells you what is happening at any particular moment. It can help determine if you are at risk of a hypoglycaemic episode (a ‘hypo’) or a hyperglycaemic episode (a ‘hyper’). You should never change any long-term medication you are taking in response to a one-off high or low reading. You should first try to work out if there is a pattern before making any changes and always talk to your diabetes care team first.

How do I control my blood glucose level?

You should control your blood glucose through a balance between food, exercise and medication.

  • Eat a healthy diet.
  • Take regular exercise.
  • Take your diabetes medication as prescribed.
  • Understand how your medication works in your body.

What do I do if my blood glucose is high?

If your blood glucose level is consistently above the target set by your diabetes care team you may be at increased risk of health problems.

You may require a change in your medication or to make changes to your diet or lifestyle to avoid hyperglycaemia. Contact your diabetes care team for advice if your blood glucose is often above target.

What do I do if my blood glucose is low?

If your blood glucose level is below 4 mmol/L you are at risk of hypoglycaemia. You may require a change in your medication or to make changes to your diet or lifestyle to avoid hypoglycaemia. Contact your diabetes care team for advice if your blood glucose is often below 4.0–4.5 mmol/L.

When should I test my blood glucose?

A diabetes doctor or nurse will discuss with you how often you should test your blood glucose. They will give you appropriate advice according to your individual requirements. The following are some general guidelines.

If your diabetes is treated with insulin, you will be asked to test your blood glucose levels more regularly. If the results are within your agreed target range then you may be able to test your blood glucose less often.

If your blood glucose levels are not in your agreed target range, you may need to adjust your insulin.

If you use a ‘basal bolus’ insulin regime (i.e. if you adjust the dose of fast-acting insulin on a daily basis depending on your diet and activity levels) then your doctor or nurse may ask you to check your blood glucose more often.

If you use this regime, you should monitor your blood glucose before meals, before you go to bed, before you drive and occasionally in the middle of the night so that you can assess your overnight insulin.

If you are on a twice-daily insulin mixture, then at first you should test your blood glucose four times a day (once before each meal and again before bed). This will allow your doctor or nurse to assess the best insulin dose for you.

This may be reduced to before breakfast and before dinner one day, and before lunch and before bedtime the next day. You should continue to test in this way, alternating each day.

When should I test my blood glucose more often?

After a change of treatment After any change of treatment, you should test your blood glucose more often to ensure that it is regulated to 4–7mmol/L. Your doctor or nurse will discuss this with you during your consultation.

During or after illness Your blood glucose may change in response to illness. If it does, then you should test it more often, around every two to four hours, especially if you are prescribed insulin. Your treatment may need to be changed. Discuss the ‘sick day guidance’ with your diabetes care team – see the Useful resources section at the end of this page.

Steroid therapy

If you are on steroid therapy, you should test your blood glucose more often. Steroids may increase your blood glucose levels. Your treatment may need to be changed.

Before conception and during pregnancy

You should test your blood glucose more often if you are pregnant or trying to conceive. Blood glucose levels of 4–6 mmol/L are desirable before and during pregnancy. Contact your diabetes care team for advice as soon as you know you are pregnant or if you are planning to become pregnant.

How to do a test

For a video tutorial of how to test your blood glucose click here

  • Wash your hands in warm water.
  • Prick the side of your finger (this is less painful).
  • Massage your finger from base to tip if necessary.
  • Place a droplet of blood on the testing strip. You should follow the instructions on the pack precisely and always check the expiry date.
  • Check visually or use a blood glucose meter.
  • Keep the meter clean and care for it by following the instructions below.
  • Record the result in your diary.

How do I look after my blood glucose meter?

  • All meters come with instructions. You should read these and follow them closely.
  • The manufacturer will normally have a helpline you can call for telephone advice.
  • Don’t forget to complete the warranty card and return it to the company.
  • It is important to quality-control your meter regularly. You can buy control solution for doing this.

Where can I get strips and lancets?

Your GP will be able to prescribe the equipment you need to use your meter.

Be in control

Testing your blood glucose levels regularly is one sure way of finding out what's happening to your body, so that you control your diabetes and it doesn’t control you.

Useful resources

For more information on HbA1c click here

For information on ‘sick day guidance’ for type 1 diabetes, click here.

For information on ‘sick day guidance’ for type 2 diabetes, click here.

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