2 Monitoring blood glucose levels
2.1 Blood glucose levels
Most people with diabetes are encouraged to keep their day-to-day blood glucose level between 4 and 7 mmol/l before meals. This is very similar to the blood glucose range of someone who does not have diabetes. However, this can be very difficult to achieve, and if you have diabetes, you should agree the ideal range for you with your diabetes team.
Two large diabetes research trials have shown that by maintaining a blood glucose range as near to the normal range as possible, the chances of developing long-term complications can be prevented, reduced or delayed. These trials were conducted in the Diabetes Control and Complications Trial (DCCT, 1993; see Box 1) and the UK Prospective Diabetes Study (UKPDS, 1998; see Box 2).
Box 1 The Diabetes Control and Complications Trial (DCCT)
This trial compared people with Type 1 diabetes who had intensive treatment to keep very good control of their blood glucose level, with people with Type 1 diabetes who had conventional treatment, and did not manage to achieve such good control. Intensive treatment involved four injections of insulin daily, frequent home blood glucose testing, regular visits to clinics, and telephone calls from diabetes nurses. The trial, which reported in 1993, was conducted in the USA over a period of nine years, with over 1000 people involved. It demonstrated very clearly that keeping good control of blood glucose dramatically reduced the risk of developing diabetes complications involving small blood vessels (i.e. microvascular complications), and slowed the progress of damage in people who already had complications like diabetic retinopathy (eye disease) and nephropathy (kidney disease).
Box 2 The UK Prospective Diabetes Study (UKPDS)
This study looked at the effect of blood glucose (and blood pressure) control in people with Type 2 diabetes. It was carried out over 20 years in the UK, reported in 1998, and involved over 3000 people. Like the results from the DCCT, it also showed that keeping good control of blood glucose reduced damage to small blood vessels and nerves. However, it concluded that even with a lot of support from the diabetes team, it can actually be very difficult to achieve good control.
The evidence from these two studies has been used to encourage people with diabetes to make and maintain lifestyle changes, take medication regularly, and to adjust insulin doses or seek advice if their blood glucose is not staying within their agreed limits. Assessing whether this is being achieved can be done in two ways: