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Effect of Continuous Glucose Monitoring on Glycemic Control in Patients With Type 2 Diabetes Treated With Basal Insulin: A Randomized Clinical Trial

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Martens, Thomas, Beck, Roy W., Bailey, Ryan, Ruedy, Katrina J., Calhoun, Peter, Peters, Anne L., Pop-Busui, Rodica, Philis-Tsimikas, Athena +66 more·2021·JAMA

Abstract

Importance: Continuous glucose monitoring (CGM) has been shown to be beneficial for adults with type 2 diabetes using intensive insulin therapy, but its use in type 2 diabetes treated with basal insulin without prandial insulin has not been well studied. Objective: To determine the effectiveness of CGM in adults with type 2 diabetes treated with basal insulin without prandial insulin in primary care practices. Design, Setting, and Participants: This randomized clinical trial was conducted at 15 centers in the US (enrollment from July 30, 2018, to October 30, 2019; follow-up completed July 7, 2020) and included adults with type 2 diabetes receiving their diabetes care from a primary care clinician and treated with 1 or 2 daily injections of long- or intermediate-acting basal insulin without prandial insulin, with or without noninsulin glucose-lowering medications. Interventions: Random assignment 2:1 to CGM (n = 116) or traditional blood glucose meter (BGM) monitoring (n = 59). Main Outcomes and Measures: The primary outcome was hemoglobin A1c (HbA1c) level at 8 months. Key secondary outcomes were CGM-measured time in target glucose range of 70 to 180 mg/dL, time with glucose level at greater than 250 mg/dL, and mean glucose level at 8 months. Results: Among 175 randomized participants (mean [SD] age, 57 [9] years; 88 women [50%]; 92 racial/ethnic minority individuals [53%]; mean [SD] baseline HbA1c level, 9.1% [0.9%]), 165 (94%) completed the trial. Mean HbA1c level decreased from 9.1% at baseline to 8.0% at 8 months in the CGM group and from 9.0% to 8.4% in the BGM group (adjusted difference, -0.4% [95% CI, -0.8% to -0.1%]; P = .02). In the CGM group, compared with the BGM group, the mean percentage of CGM-measured time in the target glucose range of 70 to 180 mg/dL was 59% vs 43% (adjusted difference, 15% [95% CI, 8% to 23%]; P < .001), the mean percentage of time at greater than 250 mg/dL was 11% vs 27% (adjusted difference, -16% [95% CI, -21% to -11%]; P < .001), and the means of the mean glucose values were 179 mg/dL vs 206 mg/dL (adjusted difference, -26 mg/dL [95% CI, -41 to -12]; P < .001). Severe hypoglycemic events occurred in 1 participant (1%) in the CGM group and in 1 (2%) in the BGM group. Conclusions and Relevance: Among adults with poorly controlled type 2 diabetes treated with basal insulin without prandial insulin, continuous glucose monitoring, as compared with blood glucose meter monitoring, resulted in significantly lower HbA1c levels at 8 months. Trial Registration: ClinicalTrials.gov Identifier: NCT03566693.

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  • Benefits of CGM in T1D include reductions in A1C, fewer severe hypoglycemia events in children and adults, increased time in range, and significant reductions in hospitalizations for severe hypoglycemia and DKA.

    “Benefits of CGM in this population include reductions in A1C, fewer severe hypoglycemia events in children and adults, increased TIR, as well as significant reductions in hospitalizations for severe hypoglycemia and DKA.156,162–168”

    From American Association of Clinical Endocrinology Clinical Practice Guideline: Developing a Diabetes Mellitus Comprehensive Care Plan-2022 Update. (2022) · cites this paper as [167]

    The Introduction says prior studies found improved glycemic control with CGM in people with type 1 diabetes. This trial’s reported A1C and time-in-range improvements concern adults with type 2 diabetes, not the claimed type 1 population; its Adverse Events section does not support fewer severe hypoglycemia events or reduced hospitalizations for hypoglycemia or DKA in children or adults with type 1 diabetes. (LLM, conf=0.83)

    Experimental — accuracy not yet measured
  • In adults with type 2 diabetes (both using and not using insulin), continuous glucose monitoring achieves improved glycated haemoglobin concentrations without impacting the rate of hypoglycaemia.

    “Continuous glucose monitoring for adults with type 2 diabetes (both those using and not using insulin)24,25 also achieves improved glycated haemoglobin concentrations without impacting the rate of hypoglycaemia.”

    From Blood glucose monitoring devices: current considerations (2023) · cites this paper as [24]

    The Abstract reports lower HbA1c with CGM, but this trial enrolled adults using basal insulin, not adults who were not using insulin. Although severe hypoglycemic events occurred in one participant per group, Other Glycemic Outcomes reports a reduction in CGM-measured hypoglycemia, so the broad claim that hypoglycemia rates were unaffected is not supported by this paper. (LLM, conf=0.90)

    Experimental — accuracy not yet measured
  • Randomized controlled trials of the use of rt-CGM, compared with standard blood glucose monitoring, in adults with type 2 diabetes have generally shown reductions in HbA 1c with no significant change in time in hypoglycemia.

    “Randomized controlled trials of the use of rt-CGM, compared with standard blood glucose monitoring, in adults with type 2 diabetes have generally shown reductions in HbA 1c with no significant change in time in hypoglycemia (169-172).”

    From Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus (2023) · cites this paper as [172]

    The Primary and Key Secondary Outcomes section reports significantly lower HbA1c with CGM than with blood glucose meter monitoring in adults with type 2 diabetes treated with basal insulin. But the Other Glycemic Outcomes section reports exploratory reductions in time below both 54 mg/dL (P = .001) and 70 mg/dL (P = .02), rather than no significant change in time in hypoglycemia. This trial also cannot establish what trials generally found. (LLM, conf=0.91)

    Experimental — accuracy not yet measured
  • RCT data on rtCGM use in individuals with type 2 diabetes on MDI, mixed therapies, and basal insulin consistently show reductions in A1C and increases in TIR but not a reduction in hypoglycemia rates.

    “RCT data on rtCGM use in individuals with type 2 diabetes on MDI (59), mixed therapies (10, 60), and basal insulin (61,62) have consistently shown reductions in A1C levels and increases in TIR (70-180 mg/dL [3.9-10 mmol/L]) but not a reduction in rates of hypoglycemia (63).”

    From 7. Diabetes Technology: Standards of Care in Diabetes—2025 (2025) · cites this paper as [61]

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Authors
Martens, T., Beck, R. W., Bailey, R., Ruedy, K. J., Calhoun, P., Peters, A. L., Pop-Busui, R., Philis-Tsimikas, A., Bao, S., Umpierrez, G., Davis, G., Kruger, D., Bhargava, A., Young, L., McGill, J. B., Aleppo, G., Nguyen, Q. T., Orozco, I., Biggs, W., Lucas, K. J., Polonsky, W. H., Buse, J. B., Price, D., Bergenstal, R. M., MOBILE Study Group, Carlson, A., Chambers, S., Yang, S., Kirkman, M. S., Kass, A., Fraser, R., Cushman, T., Ramos, C., Magar, M., Walker, M., Serafin-Dokhan, S., Salam, M., Hurst, S., Clifton, M. J., Kravarusic, J., Bansal, A., Fulkerson, C., Ang, L., Richardson, C., Mizokami-Stout, K., Reiss, J., Leone, V., Stifel, K., Dailey, G., Change, A., McCallum, J., Garcia, M. I., Davis, D., Lovell, C., Root, C., Toler, F., Wilhelm, L., Eifert, R., Murguia, L., Cota, B., Nguyen, L., Lipski, R., Lawrence, M. K., Fournier, A., Carter, M., Hoover, S., Cohen, N., Mouse, T., Rusnak, J., Campos, T., Njeru, N., Arant, T., Beck, S. E., & Balo, A.
Affiliations
  • Park Nicollet Health Services (US)
  • Jaeb Center for Health Research (US)
  • University of Southern California (US)
  • University of Michigan, Ann Arbor
  • Scripps Whittier Diabetes Institute, San Diego, California
  • Vanderbilt University Medical Center (US)
  • Emory University (US)
  • Henry Ford Health (US)
  • Iowa Diabetes Research, West Des Moines
  • University of North Carolina at Chapel Hill (US)
  • Washington University in St. Louis (US)
  • Northwestern University (US)
  • Las Vegas Endocrinology, Henderson, Nevada
  • Carteret General Hospital (US)
  • Amarillo Medical Specialists, Amarillo, Texas
  • Diabetes & Endocrinology Consultants PC, Morehead City, North Carolina
  • Behavioral Diabetes Institute, San Diego, California
  • Dexcom (United States) (US)
  • HealthPartners (US)
  • for the MOBILE Study Group
Corresponding author
Beck, Roy W.
Venue
JAMA
Published
2021-06-08
Volume
325
Issue
22
Pages
2262
ISSN
  • 0002-9955 (ISSN-L)
  • 0098-7484
OpenAlex
W3164064295
Cited by
543
References
23
Citations by year
2026: 116 · 2025: 132 · 2024: 107 · 2023: 98 · 2022: 65 · 2021: 24
FWCI
54.81
Type
journal article
Language
en
Open access
Locations
  • JAMA (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Institutes of Health (UL1TR001422)
  • National Institute of Diabetes and Digestive and Kidney Diseases (P30DK092926, P30DK020572, P30DK124723, P30DK111022)
  • National Center for Advancing Translational Sciences
Topics
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diabetes Management and Research
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diabetes Treatment and Management
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diabetes Management and Education
Keywords
continuous glucose monitoring, type 2 diabetes, basal insulin, glycemic control, HbA1c, blood glucose meters, time in target glucose range, primary care, intensive insulin therapy, glycemic variability, hypoglycemia, hyperglycemia, HbA1c reduction, HbA1c variability
MeSH terms
Glycemic Control, Aged, Blood Glucose, Diabetes Mellitus, Type 2, Female, Glycated Hemoglobin, Humans, Hypoglycemic Agents, Insulin, Male, Middle Aged, Time Factors, Confidence Intervals, Treatment Outcome, Patient Satisfaction, Sample Size, Postprandial Period

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