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#333 Come Spy with Me: Continuous glucose monitoring in diabetes


CLINICAL QUESTION
QUESTION CLINIQUE
 Compared to self-monitoring blood glucose (SMBG), does continuous glucose monitoring improve clinical outcomes or HbA1c for adults with diabetes?

BOTTOM LINE
RÉSULTAT FINAL
 Continuous glucose monitors use subcutaneous sensors and include “real-time” and “flash” monitors (described below). Real-time monitors lower severe hypoglycemic events by 2-4% compared to SMBG (to ~6% from ~8%) in type 1 diabetes, with no reported events in type 2 diabetes. Effects on HbA1c may not be clinically meaningful. Compared to SMBG, flash monitors are no different on risk of severe hypoglycemia, and HbA1c effects are inconsistent (type 1) or no different (type 2). Cost may limit use.


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EVIDENCE
DONNÉES PROBANTES
  • Systematic reviews from last five years. Minimal clinically important HbA1c change:1 0.5%. Results statistically different unless indicated.
  • Type 1 diabetes:
    • Real-time versus SMBG:
      • Eight systematic reviews [11-22 randomized controlled trials (RCTs), 1399-2461 patients]:1-8
        • Severe hypoglycemic events (requiring third-party assistance), 3 systematic reviews without significant methodological flaws.1-3 At 4-12 months: 3.5-8% versus 6.5-10% SMBG, number needed to treat (NNT)=30-55.
        • Patient satisfaction, one systematic review1 (2 RCTs, 369 patients): No difference.
        • HbA1c (mean difference): ~0.2-0.4% lower with real-time at 4-6 months.1-7
    • Flash versus SMBG at 6 months:
      • Two systematic reviews (1-2 RCTs, 64-239 patients):1,7
        • Severe hypoglycemia,1 discontinuation rates, HbA1c1,7: No difference.
      • Recent RCT (156 adults):9
        • Severe hypoglycemia: No difference.
        • HbA1c: 0.5% lower with flash.
  • Type 2 diabetes (most on insulin):
    • Real-time versus SMBG, three systematic reviews (5 RCTs, 227-439 patients):5,10,11
      • Severe hypoglycemia:5,10 None reported.
      • HbA1c: 0.25-0.5% lower with real-time over ~3-6 months.
    • Flash versus SMBG:
      • One systematic review (2 RCTs, 101-224 patients)12. At 2.5-6 months:
        • Severe hypoglycemia, HbA1c: No difference.
        • Discontinuation: 6% versus 15% (SMBG) (PEER calculation), NNT=12.
  • Limitations: Most RCTs unblinded, industry funded;13 quality of life/satisfaction inconsistently reported.
CONTEXT
CONTEXTE
  • Real-time monitors: automatically display readings (example: Dexcom 6TM); Flash monitors: manual upload required (example: Freestyle LibreTM).
    • Sensors need replacement every 7-14 days.14
  • Flash/real-time readings may lag behind SMBG by ~15 minutes.15
    • SMBG recommended before dose adjustments.1
  • Cost/year: $2500-$6000 versus $1200 for four-times daily SMBG.14,16

Uthaya somasundaram February 7, 2023

i will apply to my practice

Shashi Devi February 12, 2023

I look forward to resd ”Tools to Practice ‘

johannes malan February 13, 2023

I will keep this in mind

Patricia Chernesky February 18, 2023

Great info

gregory Stroh October 2, 2024

Interesting

Nirosha Hoover March 11, 2025

quite expensive for not much benefit it seems

Peter Clifford June 26, 2025

Convenience vs expense, with minimal impact on HbA1c.

Michael Lukenda November 1, 2025

I can’t imagine how a person with Type II DM who can check their flash monitor an unlimited number of times per day and thus determine how certain food items and portion size wouldn’t be more motivated to change their diatary habits and improve their A1c compared to having to prick their fingers several times per day

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Author(s)
Auteur(s)
  • Samantha Moe PharmD
  • Michael Kolber BSc MD CCFP MSc
  • Jamie Falk BSc(Pharm) PharmD

1. National Institute for Health and Care Excellence. Type 1 diabetes in adults: diagnosis and management, Evidence reviewed for continuous glucose monitoring in adults with type 1 diabetes. Available at: https://pubmed.ncbi.nlm.nih.gov/35593766. Accessed September 12, 2022.

2. Wang Y, Zou C, Na H, et al. Comput Math Methods Med. 2022; 2851572.

3. Teo E, Hassan N, Tam W, et al. Diabetologia. 2022; 65:604-19.

4. Dicembrini I, Cosentino C, Monami M, et al. Acta Diabetological. 2021; 58:401-410.

5. Garcia-Lorenzo B, Rivero-Santana A, Vallejo-Torres L, et al. J Eval Clin Pract. 2018; 24:772-81.

6. Benkhadra K, Alahdab F, Tamhane S, et al. Clin Endocrinol. 2017; 86:354-60.

7. Elbalshy M, Haszard J, Smith H, et al. Diabet Med. 2022; 00:e14854. DOI: 10.1111/dme.14854.

8. Maiorino MI, Signoriello S, Maio A, et al. Diabetes Care. 2020; 43: 1146-56.

9. Leelarathna, L, Evans ML, Neupane S, et al. New Engl J Med. 2022; 387:1477-87.

10. Dicembrini I, Mannucci E, Monami M, et al. Diabetes Obes Metab. 2019; 21:2619-2625.

11. Janapala RN, Jayaraj JS, Fathima N, et al. Cureus. 2019; 11(9):e5634. DOI: 10.7759/cureus.5634.

12. Castellana M, Parisi C, Di Molfetta S, et al. BMJ Open Diab Res Care. 2020; 8:e:001092.

13. CADTH. Canadian Journal of Health Technologies. 2022; 2(8): 1-50. Available at: https://www.cadth.ca/sites/default/files/pdf/htis/2022/RC1442%20rtCGM%20for%20TD1.pdf Accessed January 10, 2023.

14. Diabetes Canada. Glucose monitoring. Available at: https://www.diabetes.ca/DiabetesCanadaWebsite/media/Managing-My-Diabetes/Tools%20and%20Resources/Glucose_Monitoring_Comparison_1.pdf. Accessed December 15, 2022.

15. CADTH. Flash glucose monitoring system for diabetes. 2017 (revised Mar 2018); 158:1-15. Available at: https://www.cadth.ca/sites/default/files/pdf/eh0053_flash_glucose_monitoring_system_for_diabetes_mar2018.pdf. Accessed January 10, 2023.

16. Diabetes Canada. Coverage of self-monitoring of blood glucose (SMBG) strips. Available at: https://www.diabetes.ca/DiabetesCanadaWebsite/media/Advocacy-and-Policy/Advocacy%20Reports/Pro-Comparison-Test-Strips-Comparison-EN.pdf. Accessed December 5, 2022.

Authors do not have any conflicts of interest to declare.

Les auteurs n’ont aucun conflit d’intérêts à déclarer.