Continuous Glucose Monitors

Diabetes & endocrinology
NHS Lothian

Patients who use continuous glucose monitoring will normally use either the ‘Libre’, ‘Dexcom’ or ‘Medtronic Guardian’ system.

These sensors can remain in-situ for between 10 and 14 days and measure interstitial glucose. This means that the glucose may NOT be the same as capillary measured glucose and there is often a delay of several minutes between a capillary reading and interstitial reading.

These sensors can have pre-set alarms which alert the patient to impending hypo or hyperglycaemia

Some sensors may be linked to the patient’s insulin pump as part of a hybrid-closed-loop system

Readings can be affected by acute illness, systemic shock, and some medications (notably paracetamol, aspirin and vitamin C are known to interact with the sensors – though this should NOT STOP you prescribing these medications)

Recommended Use

DO NOT REMOVE THE SENSOR unless essential (eg for a scan or operation, or evidence of surrounding skin infection) and particularly if the patient is relying on the sensor as part of hybrid-closed-loop pump treatment or for hypoglycaemia alerts. If you remove a dexcom sensor DO NOT THROW IT AWAY – it is linked to a re-useable transmitter

PATIENT WILL NEED MINIMUM QDS CAPILLARY BLOOD GLUCOSE TESTING IN ADDITION TO CGM READINGS AS PER NORMAL HOSPITAL PROTOCOL IF ANY OF THE FOLLOWING OCCUR:

  • If the patient cannot self manage their system
  • If the patient is acutely unwell (for example shock, infection, pyrexia, hypotension, NEWS>2) as this will affect interstitial glucose
  • Hypoglycaemia – sensor glucose <4 must ALWAYS be confirmed with capillary glucose, and recovery from hypoglycaemia likewise must be confirmed with capillary glucose.
  • Hyperglycaemia – sensor glucose >14 must be confirmed with capillary glucose, and ketones must be checked.

For all patients

  • Patients who are medically stable, able to self-manage and who wish to continue to use their CGM whilst in hospital may.
  • All inpatients must have at least once daily capillary glucose checked to ensure it calibrates with the interstitial glucose measurements.
  • Please ask relatives to bring in new sensors if the patient needs to replace their sensor whilst an inpatient.