Clinical Studies

DIaMonD - A Randomized Controlled Trial Examining the Benefit of CGM Use for Adults with Type 1 Diabetes on Insulin Injections

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DIaMonD Study1 shows that Dexcom CGM use improves glucose control in adults with type 1 diabetes using insulin injections.

DIaMonD Type 1 Study Highlights (pdf)


Clinical trials demonstrating improved glucose control in type 1 patients using CGM have historically and predominantly involved participants who use insulin pump therapy and not insulin injections (MDI).2 However, most type 1 adult patients deliver insulin by injection.3


Examine effectiveness of CGM vs. self-monitoring of blood glucose (SMBG) with blood glucose meter in adults with type 1 diabetes on MDI insulin therapy.

Primary endpoint: Change in A1C

Research Design/Methods

24-week, randomized, controlled trial of 158 adults with type 1 diabetes. Study conducted using the Dexcom G4® PLATINUM CGM System, which uses the same software 505 as the Dexcom G5® Mobile CGM System.

  • Group 1: MDI + CGM (n=105)
  • Group 2: MDI + SMBG (n=53)
  • Baseline A1C was 8.6% (range 7.5 to 9.9%)
  • Various education (with 45% less than a bachelor’s degree) and numeracy levels (ability to use math in daily diabetes management decisions)

Patient Education/Touchpoints

All participants received the same basic diabetes education. Intensive diabetes education and device training was NOT a part of this study. Study was 6 months in length and used a protocol with minimal “touch” reflecting common clinical practice.


The trial was conducted at 24 endocrinology practices in the USA (19 community-based and 5 academic centers).


Significant A1C reduction in type 1 patients on insulin injections with Dexcom CGM use

In study participants using Dexcom CGM:
Overall: Average 1% A1C reduction after 24 weeks of regular use, compared 
to baseline (difference of 0.6% compared to SMBG group [p-value <.001]).

  • ≥1% A1C reduction for 52% of patients
  • Participants with a baseline A1C of ≥8.5%: Average 1.3% A1C reduction compared to baseline
Dexcom CGM increased time spent in range from baseline (70 - 180 mg/dL):
  • CGM group: Median 1.3 additional hours (+76 mins) in range
  • SMBG group: No increase of time in range
  • 4% reduction in glycemic variability with CGM group compared to SMBG group.
Dexcom CGM use reduced time in hyperglycemia.
  • CGM group: 40% reduction of time spent in severe hyperglycemia (>300 mg/dL)†
  • SMBG group: Median increase of 58 minutes spent in severe hyperglycemia
Dexcom CGM use reduced time in hypoglycemia.
  • 37 less minutes/day <70 mg/dL; 49% reduction from baseline
  • 20 less minutes/day <60 mg/dL; 53% reduction from baseline
  • 14 less minutes/day <50 mg/dL; 69% reduction from baseline

Dexcom CGM use reduced nighttime hypoglycemia (<60 mg/dL):

  • CGM group: 79% reduction in the median time spent in hypoglycemia at night, from 2.9-0.6%.
CGM Use and Adherence
  • Age, education and numeracy level did not show any difference in A1C reduction with MDI and CGM. All subgroups lowered their A1C by 1.0%.
  • 93% of patients were using the Dexcom CGM ≥ 6 days/week (at week 24).

† Investigators pooled data from weeks 12 and 24; Δ time (median minutes/day): [pooled data - baseline data]

DIaMonD Type 1 Study Highlights (pdf) 

1 Beck RW, Riddlesworth T, Ruedy K, et al. Effect of Continuous Glucose Monitoring on Glycemic Control in Adults With Type 1 Diabetes Using Insulin Injections: The DIAMOND Randomized Clinical Trial. JAMA. 2017;317(4):371–378. doi:10.1001/jama.2016.19975. View full article.

2 Bergenstal RM, Tamborlane WV, Ahmann A,  et al; STAR 3 Study Group.  Effectiveness of sensor-augmented insulin-pump therapy in type 1 diabetes.  N Engl J Med. 2010;363(4):311-320.

3 Grunberger G, Abelseth JM, Bailey  TS,  et al.  Consensus statement by the American Association of Clinical Endocrinologists/American College of Endocrinology Insulin Pump Management Task Force.  Endocr Pract. 2014;20(5):463-489.

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