continuous glucose monitoring (CGM)

Last edited 03/2023 and last reviewed 05/2023

Subcutaneous continuous glucose monitoring (CGM)

• has proven benefit in type 1 diabetes (1)
  • various designs (1,2)
  • continuous glucose monitors (3,4,5)
    • are devices that offer an alternative to finger stick blood glucose testing in adults and children with any type of diabetes (age suitability may vary by product)
    • typically requires the person to wear a small, disposable subcutaneous sensor that measures interstitial glucose levels for 7-14 days or more
    • glucose levels are recorded at frequent intervals (typically 1-5 minutes) transmitted to a receiver or smart device
    • being used in automated insulin delivery systems, where an algorithm uses CGM data to adjust insulin dosing via a connected insulin pump
    • real-time CGM, which provides real-time alerts and transmits glucose data continuously
    • intermittently scanned CGM (isCGM, previously known as "flash" glucose monitoring)
      • typically provides glucose data "on demand," when scanned by a receiver or smart device - some earlier versions have no alarm capabilities
    • CGM in pregnancy
      • normal birth weight is associated with achieving significantly lower mean CGM glucose concentration across the 24-h day and higher CGM time in range from before the end of the first trimester, emphasizing the need for a shift in clinical management, with increased focus on using weekly CGM glucose targets for optimizing maternal glycemia from early pregnancy
    • accuracy of CGM is close to that of finger stick blood glucose testing (3)
      
      
    • NICE recommendations for intermittently scanned CGM have been made aimed at a defined group of adults with type 2 diabetes who use insulin to manage their diabetes, particularly those who have recurrent or severe hypoglycaemia, impaired hypoglycaemia awareness, or a condition or disability that means they cannot self monitor their blood glucose levels and require input from carers(5)
      • adults with type 1 diabetes
        • offer adults with type 1 diabetes a choice of real-time continuous glucose monitoring (real-time CGM) or intermittently scanned continuous glucose monitoring (isCGM, commonly referred to as "flash"), based on their individual preferences, needs, characteristics, and the functionality of the devices available
      • adults with type 2 diabetes
        • offer intermittently scanned continuous glucose monitoring (isCGM, commonly referred to as “flash”) to adults with type 2 diabetes on multiple daily insulin injections if any of the following apply:
          • they have recurrent or severe hypoglycaemia
          • they have impaired hypoglycaemia awareness
          • they have a condition or disability (including a learning disability or cognitive impairment) that means they cannot self monitor their blood glucose by capillary blood glucose monitoring but could use an intermittently scanned CGM device (or have it scanned for them)
          • they would otherwise be advised to self measure at least eight times a day
        • offer intermittently scanned CGM to adults with insulin-treated type 2 diabetes who would otherwise need help from a care worker or healthcare professional to monitor their blood glucose
      • consider real-time continuous glucose monitoring (rtCGM) as an alternative to intermittently scanned CGM for adults with insulin-treated type 2 diabetes if it is available for the same or lower cost

Reference:

• Yeh HC, Brown TT, Maruthur N, et al. Comparative effectiveness and safety of methods of insulin delivery and glucose monitoring for diabetes mellitus: a systematic review and meta-analysis. Ann Intern Med 2012;157:336-47
• Cohen N. Continuous glucose monitoring and pumps.Aust Fam Physician. 2015 May;44(5):284-7.
• Lewis D M, Oser T K, Wheeler B J. Continuous glucose monitoring BMJ 2023; 380 :e072420 doi:10.1136/bmj-2022-072420
• Scott EM et al. Continuous Glucose Monitoring Metrics and Birth Weight: Informing Management of Type 1 Diabetes Throughout Pregnancy. Diabetes Care 2022; dc220078. https://doi.org/10.2337/dc22-0078
• Mulvihill C, Brooks A, Basudev N, Lincoln P. Continuous glucose monitoring for adults and children with diabetes: summary of updated NICE guidance BMJ 2022; 379 :o2418