Blood Glucose Monitoring
Contents:
- Why check my blood glucose?
- How do I check my blood glucose?
- Who should be monitoring?
- When should I check my glucose levels?
- When should I check my blood glucose levels more often?
- Blood glucose targets
- How do I control my blood glucose?
- What should I do if my blood glucose is high?
- What should I do if my blood glucose is low?
- Useful resources
Why check my blood glucose?
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Monitoring blood glucose 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 low blood glucose (hypoglycaemia, also known as a ‘hypo’) or high blood glucose (also known as hyperglycaemia). Checking your blood glucose regularly shows you how lifestyle changes and medication affect your levels and helps you maintain control of your diabetes. High glucose levels increase your risk of developing health issues such as heart, kidney and eye diseases, nerve damage, stroke and poor circulation. |
The closer the blood glucose is to recommended levels, the better.
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 check my blood glucose?
Blood glucose is checked either using finger prick monitoring or through technology such as continuous glucose monitors (CGM).
What is HbA1c
Whilst blood glucose monitoring gives you a reading at a particular point in time, your HbA1c is the average blood glucose level for the last 2-3 months. You find out your HbA1c level by getting a blood test from your doctor or nurse. For more information on HbA1c, click here.
Who should be monitoring glucose levels?
Self-monitoring is most appropriate for:
- people with type 1 diabetes
- people with type 2 diabetes who use insulin or tablets that can cause hypoglycaemia
- women who are pregnant, and have type 1, type 2 or gestational diabetes
- people with type 3c diabetes (also known as “pancreatic” or “pancreatogenic” diabetes)
No glucose monitoring is required for:
Many people with type 2 diabetes, especially those who manage their diabetes through diet or who are using certain tablets (such as metformin or pioglitazone, 'gliptins or 'gliflozins) or non-insulin injections ('glutides, tirzapetide) do NOT need to check their blood glucose routinely.
There is no risk of low blood glucose (hypoglycaemia) unless these medications are taken alongside other medications that can cause hypoglycaemia (see below). Blood glucose control is better monitored by regular HbA1c testing.
Occasional glucose monitoring required:
For people with type 2 diabetes who are taking tablets that can cause low blood glucose (e.g. gliclazide, glipizide [sulphonylureas] and repaglinide [meglitinides]), blood glucose testing may be required if:
- you have any symptoms of low blood glucose (hypoglycaemia),
- if you are having repeated hypoglycaemic episodes
- to ensure you are safe to drive
- during illness when glucose levels may be more erratic.
Monitoring glucose levels may also help you better understand the impact of certain foods and activities on your glucose levels. Contact your diabetes care team if you need advice on home blood glucose meters.
When should I check my blood glucose?
A diabetes doctor or nurse will discuss with you whether you need to check your blood glucose and if so, how often to do so. They will give you appropriate advice according to your individual requirements. The following are some general guidelines.
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If your diabetes is treated with insulin: you will be asked to check your blood glucose levels more regularly. If the results are within your agreed target range then you may be able to check your blood glucose less often. If your blood glucose levels are not in your agreed target range, you may need to adjust your insulin. |
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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 check your overnight insulin requirements. |
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If you are on a twice-daily insulin mixture: at first you should monitor your blood glucose four times a day (once before each meal and again before bed). This will allow your doctor or nurse to advise the best insulin dose for you. This may be reduced to before breakfast and before dinner every day, or alternating between this pattern and checking before lunch and before bedtime. |
When should I monitor my blood glucose more often?
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After a change of treatment |
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Illness |
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Steroid therapy |
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Before conception and during pregnancy Contact your diabetes care team for advice if you are planning to become pregnant and as soon as you know you are pregnant. |
Blood glucose target levels
Blood glucose targets are individual to each person, and you should agree your own target levels with your diabetes care team. The graphics below give you a general guide for target levels for when you wake up and before meals:
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The target blood glucose ranges in Table 1 below (from national guidelines) are to be used as a guide only and give different levels for different groups:
Table 1: Target blood glucose ranges
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Waking |
Before meals |
Two hours after meals |
Bedtime |
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Children: type 1 diabetes* |
4–7 mmol/L |
4–7 mmol/L |
5–9 mmol/L |
6 – 8mmol/L |
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Adults: type 1 diabetes* |
5–7 mmol/L |
4–7 mmol/L |
5–9 mmol/L |
6 – 8mmol/L |
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Type 2 diabetes** |
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4–7 mmol/L |
less than 8.5 mmol/L |
5 – 8mmol/L |
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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) |
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*National Institute of Clinical Excellence (NICE) 2015
** Diabetes UK Council of Health Care Professionals 2015
How do I control my blood glucose level?
You should control your blood glucose through a balance between food, exercise and medication. This includes:
- Eating a healthy diet
- Taking regular exercise
- Taking your diabetes medication as prescribed
- Understanding how your medication works in your body
What do I do if my blood glucose is high?
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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 need a change in your medication or to alter your diet or lifestyle to avoid hyperglycaemia. Contact your diabetes care team for advice if your blood glucose is often above target. |
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What do I do if my blood glucose is low?
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Hypoglycaemia (low blood glucose) is defined as a glucose level below 4 mmol/L. You may require a change in your medication or to alter your diet or lifestyle if you are noticing regular hypoglycaemia. |
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The video below explains more about hypoglycaemia and how to treat it:
Contact your diabetes care team for advice if your blood glucose is often below 4–4.5 mmol/L.
Useful resources
For information on ‘sick day guidance’ for type 1 diabetes, click here.
For information on ‘sick day guidance’ for type 2 diabetes, click here.
