Continuous glucose monitoring systems
Continuous glucose monitoring (CGM) systems measure the glucose concentration in interstitial fluid every few minutes. They can display real-time glucose concentration measurements and alert the user to high or low concentrations. Some devices can communicate with a continuous subcutaneous insulin infusion (CSII) pump, allowing use as a sensor-augmented CSII pump. CGM is possibly most beneficial when it is linked with a CSII pump to form a hybrid closed-loop system. CGM can also be useful for patients using a multiple daily injection (basal–bolus) insulin regimen. Some CGM systems require calibration with capillary (finger-prick) blood glucose concentration readings.
In patients with type 1 diabetes, CGM can help to reduce HbA1c and, in those at high risk of hypoglycaemia, reduce the risk of hypoglycaemia. To confer a metabolic benefit, CGM must be used more than 80% of the time.
CGM is sometimes used by specialist units for short periods (eg 1 week) for patients with:
- hypoglycaemia unawareness
- recurrent severe hypoglycaemia
- suspected nocturnal hypoglycaemia
- mismatch between HbA1c and blood glucose concentration monitoring results
- a licence to drive a commercial vehicle whose fitness to drive is being assessed.
At the time of writing, the National Diabetes Services Scheme (NDSS) subsidises CGM systems for:
- children and people younger than 21 years with type 1 diabetes
- children and people younger than 21 years with conditions very similar to type 1 diabetes who require insulin
- women with type 1 diabetes who are actively planning pregnancy, pregnant or immediately post-pregnancy
- people with type 1 diabetes aged 21 years or older who have concessional status.