Diabetes Type 2

Testing blood glucose - monitoring diabetes

There are two sorts of blood glucose tests for people with diabetes. The HbA1c test which is done by a health professional and the 'finger-prick test' which you can do for yourself.

The HbA1c or glycated haemoglobin test is usually done once a year by the GP or specialist nurse as part of the annual check-up for people with type 2 diabetes (see 'Care and treatment for type 2 diabetes'). The test measures the amount of glucose that the body's red blood cells are carrying and indicates how blood glucose levels have been over the previous 2 or 3 months. If the result is high the test can be repeated in a few months after changes in diet or treatment.

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The finger-prick test gives an instant reading or snapshot of the glucose level in the blood at that moment which indicates whether your diabetes is under control. Regular testing had made many people we talked to more aware of foods they needed to limit or avoid altogether, and that exercise could help to reduce blood glucose levels. 

Many people with diabetes feel that they are bound to have better control of their blood sugar if they can monitor it themselves on a regular basis. But several large studies have failed to confirm this, and found that regular monitoring by people who are not taking insulin often increases anxiety about normal ups and downs in blood glucose levels without improving long-term control. A large part of the NHS annual spend on diabetes is taken up by the inappropriate use of blood testing strips, so in many parts of the UK there are local guidelines aimed at restricting their availability to appropriate levels for each stage of diabetes.

Blood glucose targets

Everyone with diabetes is advised to try to keep their blood glucose levels steady and within the recommended range. For most people with diabetes this is below 48mmol/mol (6.5 mmol/l*) (NICE guidelines for type 2 diabestes 2016). The 2016 NICE Type 2 diabetes guidelines do not contain recommendations for fasting and postprandial (before and after meals) blood glucose targets. However, Diabetes UK Council of Healthcare Professionals (CHP) has advised that the general targets recommended by NICE in the Type 2 diabetes 2008 guidelines be maintained as a guide.

The NICE – National Institute for Health Care Excellence guidelines for type 2 diabetes (2008) recommends that people with type 2 diabetes should aim for 
•    4–7mmol/l* before meals (20-53 mmol/mol)
•    less than 8.5mmol/l two hours after meals (69 mmol/mol):

It is important that individual blood glucose levels should be agreed between the person and their diabetes team. Normal blood glucose levels e.g. for someone without diabetes are 3.5 -5.5mmol/l before meals (15-37 mmol/mol) and under 8mmol/l (64 mmol/mol) 2 hours after meals.

*millimoles per litre: a measurement of the concentration of a substance in a given amount of liquid

Testing blood glucose is particularly important when you are feeling unwell for any reason or if blood glucose levels are unstable. If blood glucose levels dip too low, usually below 4 mmol/l, that is hypoglycaemia (Diabetes UK 2016). Too much glucose in the bloodstream is called hyperglycaemia (hyper). Both hypos and hypers can, if left untreated, lead to coma (see 'Managing hypos').

For those who checked their blood glucose levels regularly - the 'finger prick' test - few had any difficulty with the procedure itself. Most had been given or had bought their own blood glucose meter which read their glucose levels automatically.

After the initial period of adjustment, some people on oral medication such as metformin chose to carry on testing themselves daily because they felt it helped keep them on the right track and helped them understand the relationship between food, exercise and blood glucose levels. There are no firm rules about whether those taking anti-diabetes tablets should or should not measure their blood glucose regularly; if you are in any doubt about what you should be doing ask your GP. However, people on insulin should test their blood glucose every day, ideally before each injection so that they know how much insulin they need to keep their glucose level stable.

Not everyone wanted to test their blood glucose regularly; some people on oral medication had been advised not to check their levels in case they became over-anxious. The cost of test strips also put some people off routine testing.

Once they had got their medication right, some people stopped testing blood glucose as regularly as before. Several people admitted that they hardly ever tested their blood glucose levels and increased or lowered their insulin by physical signs such as tingling in the lips even though they knew doctors don't recommend this.

Last reviewed March 2016.
Last updated March 2016.

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