All about glucose testing

Why should you test your glucose levels? It’s a good question. Testing your glucose can be a pain (literally, if you use a finger-prick test) and hard to remember to do regularly. And a glucose test is just that; it tells you what’s going on, but doesn’t treat your diabetes. So why bother?

Before throwing away your testing kit, have a look at the evidence. Studies show people with Type 1 diabetes who test their glucose frequently tend to have a lower HbA1c – the reliable measure of blood glucose control over 2-3 months –  than those who don’t.1

What if you ‘just know’ whether your glucose is high or low? Research suggests feelings may be unreliable. In one study, only a third of participants asked to guess their glucose level before testing got it about right.2

How else can testing my glucose benefit me?

When you’re managing your diabetes every day, testing your glucose is important to balance meals and exercise with insulin, to prevent your glucose level going too high (hyperglycaemia) or to avoid hypoglycaemia (a hypo). It’s likely you focus on your HbA1c as a guide to how well you’re doing in the longer term.

But there’s an exciting new clinical approach to the way you think about what treatment ‘success’ means. The Triangle of Diabetes Care, developed by diabetes specialist Dr Ramzi Ajjan, suggests you focus on not one treatment goal, but three.

As well as aiming to keep your glucose levels within target, the Triangle of Diabetes Care has two more goals:

  • Having fewer hypos
  • Minimising swings between low and high glucose  

Evidence shows that, together with keeping an eye on your HbA1c, aiming for these two additional goals reduces the risk of long-term complications and can improve overall health and wellbeing.

How does glucose testing fit in with The Triangle of Diabetes Care?

Testing your glucose regularly can help you get a detailed picture of how your glucose levels respond to the meals you eat and your activities throughout the day.

The records you build up by logging your results in your glucose testing system can also help you spot patterns, for example:

  • You often go low after playing football
  • Your glucose levels go up and down unpredictably before exams

With the data you need to hand, you can review your results with your diabetes care team and decide what steps to take – for example, having a bigger snack before football, or planning ways to tackle exam-time stress. 

Managing all three goals well can benefit your overall control. And if you don’t achieve one of the goals, an improvement in one or both of the others is good news too, to help avoid long-term complications and improve daily life with diabetes. It’s a win win win! 3,4,5,6,7,8


What should my glucose be?

NICE (the National Institute of Health and Care Excellence) recommends these targets for adults with Type 1 diabetes:9


Before breakfast ('fasting') 

5 to 7 mmol/L
Before meals at other times of the day 4 to 7 mmol/L
90 - 2 hours after meals 5 to 9 mmol/L

These numbers are a guideline. Everyone’s diabetes is different and your care team should discuss your targets with you.

How should I test my glucose levels?

Not everyone with diabetes is advised to monitor their own glucose levels. If you have Type 2 diabetes that’s managed with diet, exercise or medications such as metformin that don’t increase your risk of hypoglycaemia, it’s not usually recommended.10

Hand-held blood glucose meters used to be the only option for glucose testing at home. But now there are exciting devices available that largely do away with finger-prick testing and are transforming the way people manage their diabetes. These are:

It’s important to choose the glucose testing system that’s right for you, so talk to your diabetes care team about it.

How does continuous glucose monitoring work?

A continuous glucose monitoring (CGM) system consists of:

  • a small disposable sensor inserted into the skin
  • a wireless transmitter connected to the sensor
  • a receiver that displays results.

Unlike blood glucose meters, a CGM sensor measures the glucose in your interstitial fluid (the fluid between your cells). The readings aren’t always exactly the same as blood glucose so you’ll still need to do finger-prick tests, but not as often.12

A CGM works 24 hours a day and can include alarms to alert you when your glucose levels are too high or too low.  

CGM devices aren’t routinely available on the NHS. Some people find it helpful to use them for a short time, for example to find out what’s going on if glucose levels are very unstable.11

How does flash glucose monitoring work?

The FreeStyle Libre system from Abbott is a unique product in the world of glucose testing.

Unlike blood glucose meters, the FreeStyle Libre system measures the glucose in your interstitial fluid (the fluid between your cells). There’s no need for routine12 finger pricks, as you wear a small sensor on the back of your upper arm that lasts for up to 14 days.

You can use a hand-held reader or a compatible mobile phone13 (app download is required) to scan the sensor any time15 for a result in a second, even through your clothes.14 The sensor is waterproof so you can wear it while showering or swimming17, and it’s discreet. You can test wherever you like without worrying about mess and inconvenience. 

Each scan you take gives your current glucose reading, a view of the last eight hours and a trend arrow shows18 which way you're heading.16  The FreeStyle Libre system works with a cloud-based system called LibreView19 that allows you to store your data and quickly turn the numbers into reports you can share with your diabetes care team.

The FreeStyle Libre system is approved by the NHS for measuring interstitial fluid glucose levels in people (age 4 and older) with diabetes mellitus, including pregnant women. The indication for children (age 4-12) is limited to those who are supervised by a caregiver who is at least 18 years of age. The caregiver is responsible for managing or assisting the child to manage the FreeStyle Libre Flash Glucose Monitoring System and also for interpreting or assisting the child to interpret FreeStyle Libre readings. Find out more about the FreeStyle Libre system.

product family


1. Miller, KM et al, 2009, Evidence of a strong association between frequency of self-monitoring blood glucose and haemoglobin A1c levels in Type diabetes exchange clinic registry participants, Diabetes Care 36: 2009-2014, 2013, accessed 27 March 2019 from

2. Frankum, S; Ogden, J, 2005, Estimation of glucose levels by people with diabetes: a cross-sectional study, British Journal of General Practice, Dec 1; 55(521): 944-948, accessed 27 March 2019 from

3. Shafiee, G et al, 2012, The importance of hypoglycaemia in diabetic patients, Journal of Diabetes and Metabolic Disorders, 11: 17, accessed June 25 2019 from

4. Kilpatrick, ES et al, 2008, Mean blood glucose compared with HbA1c in the prediction of cardiovascular disease in patients with type 1 diabetes, Diabetologia, 51: 365-371, accessed June 25 2019 from

5. Lin, CC et al, 2012, Variation of fasting plasma glucose: a predictor of mortality in patients with type 2 diabetes, American Journal of Medicine,125: 416.e9-18, accessed June 25 2019 from

6. Ceriello, A et al, 2014, Hyperglycaemia following recovery from hypoglycaemia worsens endothelial damage and thrombosis activation in type 1 diabetes and in healthy controls, Journal of Nutrition, Metabolism and Cardiovascular Disease, 24: 116-123, accessed June 25 2019 from

7. Currie, CJ et al, 2010, Survival as a function of HbA1c in people with type 2 diabetes: a retrospective cohort study, The Lancet, 375: 481-489, accessed June 25 2019 from

8. Stratton, MI et al, 2000, Association of glycaemia with macrovascular and microvascular complications of type 2 diabetes (UKPDS 35): prospective observational study, British Medical Journal, 321: 405-412, accessed June 25 2019 from

9. National Institute of Health and Care Excellence 2019, NG17. Type 1 diabetes in adults: diagnosis and management, accessed 7 April 2019,

10. National Institute of Health and Care Excellence 2019, Managing blood glucose in Type 2 diabetes in adults, accessed 7 April 2019,

11. Diabetes UK 2019, Continuous glucose monitoring, accessed 27 March 2019,

12. A finger prick test using a blood glucose meter is required during times of rapidly changing glucose levels when interstitial fluid glucose levels may not accurately reflect blood glucose levels, or if hypoglycemia or impending hypoglycemia is reported but the symptoms do not match the system readings.

13. The FreeStyle LibreLink app and the FreeStyle Libre reader have similar but not identical features. A finger prick test using a blood glucose meter is required during times of rapidly changing glucose levels when interstitial fluid glucose levels may not accurately reflect blood glucose levels or if hypoglycaemia or impending hypoglycaemia is reported by the FreeStyle LibreLink app or when symptoms do not match the app readings. The FreeStyle Libre sensor communicates with the FreeStyle Libre reader that started it or the FreeStyle LibreLink app that started it. A sensor started by the FreeStyle Libre reader will also communicate with the FreeStyle LibreLink app. The FreeStyle LibreLink app is compatible with NFC-enabled smartphones running Android OS 5.0 or later and with iPhone 7 and later running OS 11 and later.Use of FreeStyle LibreLink requires registration with LibreView, a service provided by Abbott and Newyu, Inc.

14. The reader can capture data from the sensor when it is within 1cm to 4cm of the sensor.

15. 60-minute warm-up required when applying the sensor

16. For a complete glycaemic picture, scan once every 8 hours.

17. Sensor is water resistant in up to 1 meter (3 feet) of water Do not immerse longer than 30 minutes. Not to be used above 10,000 feet.

18. Trend arrow may not show with every reading

19. LibreView is developed and distributed by Newyu, Inc.



This is the Republic of Ireland Abbott Diabetes Care website

If you'd like to see country-specific content relevant to you, please visit our list of global websites, or....

• • • • • • • •