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Blood glucose monitoring in diabetes

Key learning points:

 -  Self-monitoring should be used by the individual to make effective changes to their medication and/or lifestyle

 -  Insulin and sulphonylureas can cause hypos which can be detected by self-monitoring.

 -  Monitoring needs to be done at relevant times of day to be effective

The number of people with diabetes is on the increase, especially type 2 diabetes. Regardless of how much time is spent with the healthcare team to care for this condition, the individual with diabetes self-manages 24 hours a day, 365 days a year. One tool people with diabetes may utilise is self-monitoring of blood glucose (SMBG), but this needs to done effectively to avoid wasting valuable resources. There is some debate as to who should use SMBG.

The number of blood glucose monitoring items prescribed has increased. In 2011-12 it represented almost 15% of all items prescribed for diabetes, and 20.8% of the total cost of prescribing for the treatment of diabetes.1 This makes it more costly than most of the traditional therapies for diabetes and, it can be argued, does not give value for money in all cases. SMBG is only useful if the individual patient understands the results and is prepared to take action on those results.

There is increasing concern that health service managers and GPs are using recently-published evidence to prevent even those individuals who find blood glucose monitoring useful from checking their blood glucose.2 There should be no debate for people with type 1 diabetes - they need to monitor if they are able.

On the one hand SMBG is seen as an expensive option with little evidence to support it; on the other it is seen as a vital tool in engaging people with diabetes in their own care. The evidence is not strong for either argument.3-8

Who should test and how often?

It is impossible to dictate how often a person with diabetes should test. It depends on:

 - Type of diabetes.

 - Current therapy.

 - How willing/capable they are of acting on the results.

- Whether they drive (relevant for those who could be subject to hypoglycaemia).

 - Level of control.

Involving the person with diabetes in setting self-monitoring goals and targets should be the norm. They should recognise that SMBG is an educational tool that is available to them and to use it wisely. It should not simply be a paper record they bring to you for interpretation. Three questions to consider asking to aid effective use of strips include:

  1. Tell me why you did that test.

  2. What did you learn from the result?

  3. What action did you take?

If they cannot answer these questions, perhaps they need to be more involved in education and meaningful goal setting, or perhaps they are gaining little from self-monitoring.

Although SMBG is a vital part of the management of blood glucose levels in people with type 1 diabetes, many people with type 1 and type 2 diabetes do not routinely monitor glucose levels either post-prandially (after meals) or overnight, which may leave undetected episodes of hyperglycaemia and hypoglycaemia respectively.9 Consider the person whose monitoring diary shows exemplary control pre meals (fasting levels) but has a high HbA1c. If HbA1c remains above target but pre-meal self-monitoring levels remain well controlled (8.5 mmol/litre), and manage to below this level if detected. 

Fasting and/or pre-meal levels are a good indication of effectiveness of therapy, but post-meal spikes can be an indicator of future cardiovascular risk. The International Diabetes Federation has published guidance on post-meal testing.10

Hypoglycaemia (hypo) risk

There is little debate on the need for people with type 1 diabetes to self-monitor their blood glucose as the majority of them use that information to alter their insulin doses and to detect potential hypos and treat them accordingly. The National Institute for Health and Care Excellence (NICE)11 acknowledge that and furthermore advises that SMBG is an essential element of self-care if backed by education.

It is important to recognise that people treated with sulphonylureas are also at risk of hypoglycaemia. A recent important study indicated that around 7% of individuals taking sulphonylureas (usually gliclazide in the UK) with a mean HbA1c of 58mmol/mol (7.5%) experienced at least one severe episode over 9-12 months; a rate comparable to people with type 2 diabetes recently started on insulin therapy.12 There is therefore a strong case that SMBG should also be provided to individuals taking sulphonylureas (see driving section later).

Reliance on HbA1c as a marker of long-term glycaemic control is an accepted practice, but self-monitoring data and patient history should also be taken into consideration as frequent hypoglycaemic events may result in a low HbA1c level, while adversely affecting quality of life.

People with diabetes who suffer repeated highs and lows in their SMBG can now be referred for continuous glucose monitoring system (CGMS) by means of subcutaneous sensors which measure interstitial glucose levels. Using plotted results taken every few minutes, specialists can assess their control in relation to their therapy and make effective adjustments.

A note on driving

The Driver and Vehicle Licensing Agency (DVLA) has updated its guidance on blood glucose monitoring for drivers treated with insulin. Main facts are:

 - Must have awareness of hypoglycaemia.

- Must not have had more than one episode of hypoglycaemia requiring the assistance of another person in the preceding twelve months.

 - There must be appropriate blood glucose monitoring. 

 - It also includes advice for those treated with sulphonylureas who have hypos. The full publication is available as a free download (see References).13

- Must not have had more than one episode of hypoglycaemia requiring the assistance of another person within the preceding 12 months. 

- It may be appropriate to monitor blood glucose regularly and at times relevant to driving to enable the detection of hypoglycaemia. 

 

Quality Control

The Medicines and Healthcare Products Regulation Agency (MHRA) has published updated guidance for healthcare professionals to ensure accuracy on blood glucose meters14 including where to report any adverse incidents. It also issues alerts on problems with meters. 

 

References 

1. Prescribing for Diabetes in England. 2006/6 to 2011/12 NHS Information Centre 2012

2. NHS Diabetes. Self monitoring of blood glucose in non-insulin-treated Type 2 diabetes. 

3.   Martin S, Schneider B, Heinemann L, et al. Self-monitoring of blood glucose in type 2 diabetes and long-term outcome: an epidemiological cohort study. Diabetologia 2006;49:271-8.

4. Peel ED, Lawton J. Self monitoring of blood glucose in type 2 diabetes: longitudinal qualitative study of patients' perspectives. BMJ 2007;335:493.

5. Simon J, Gray A, Clarke P, et al. Cost effectiveness of self monitoring of blood glucose in patients with non-insulin treated type 2 diabetes: economic evaluation of data from the DiGEM trial. BMJ 2008;336:1177-80.

6. Farmer AJ, Wade AN, French DP, et al. Blood glucose self-monitoring in type 2 diabetes: a randomised controlled trial. Health Technol Assess 2009;13:iii-iv, ix-xi, 1-50.

7. O'Kane MJ, Bunting B, Copeland M, et al. Efficacy of self monitoring of blood glucose in patients with newly diagnosed type 2 diabetes (ESMON study): randomised controlled trial. BMJ 2008;336:1174-7.

8. Parkin C, Hinner D, Terrick D. Effective Use of Structured Self-Management of Blood Glucose in Type 2 Diabetes: Lessons From the STeP study. Clinical Diabetes 2011;29(4):131-8.

9. Scottish Intercollegiate Guidelines Network. Management of Diabetes: A National Clinical Guideline. Edinburgh: SIGN; 2010.

10. International Diabetes Federation. Guideline for Management of Post-Meal Glucose in Diabetes. 2011.

11. NICE. Management of Type 2 Diabetes. London: NICE; 2009.

12. UK Hypoglycaemia Study Group. Risk of hypoglycaemia in types 1 and 2 diabetes: effects of treatment modalities and their duration. Diabetologia 2007;50:1140-7.

13. DVLA. At a Glance Guide to the current Medical Standards of Fitness to Drive. 

14. MHRA. Point of care testing - blood glucose meters. 2011.