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Type 1 Diabetes

Does a CGM Actually Lower Your A1c? The Real Numbers

· 3 min read · Reviewed by GlucIQ Clinical Review Workflow
#cgm#a1c#cluster:cgm-trials

“Just get a CGM” is the standard advice now. But if you’re paying for it yourself — or convincing a hesitant doctor — you want the actual numbers.

Here they are. Two of the biggest trials ever run on CGM for people on insulin injections, and what they found.

DIAMOND: the US trial

DIAMOND tested CGM in adults with type 1 on multiple daily injections — the exact group people used to say “doesn’t need a CGM.”

The result: CGM users lowered their A1c by about 0.6% compared to people using fingersticks (Beck et al., 2017, DIAMOND). And they did it with no change in their insulin doses — just better information.

0.6% might sound small. It’s not. That’s roughly the difference between a 7.8% and a 7.2% A1c — the difference between “okay” and “good” — from a device, not a new insulin.

GOLD: the Scandinavian trial

GOLD was a crossover trial — everyone got both CGM and fingersticks, so each person was their own comparison.

The result: CGM improved A1c and time in range (Lind et al., 2017, GOLD). Same direction, same message — CGM moves the needle even in people already trying hard.

What the numbers mean for you

  • If you’re on injections, CGM helps — a lot. The old belief that CGM only helped pump users is gone. DIAMOND and GOLD both studied injection users (Beck et al., 2017; Lind et al., 2017).
  • The improvement comes from visibility. You see patterns you can’t see with 4 fingersticks a day — the 2am low, the 11am climb, the pizza wave. See it, fix it.
  • It’s not automatic. The trials show the average gain. People who reviewed their data and acted got the most.

The honest caveats

  • Wearing it isn’t enough. The trials’ participants engaged with the data. A CGM in a drawer does nothing.
  • Alarm fatigue is real. Some people turn it off or tune it down — which is fine, but it costs some of the benefit.
  • Cost and access are still barriers for many. If you can’t get one, structured fingerstick testing (checking at set times and patterns) still helps.

The one-minute takeaway

The data is clear: CGM lowers A1c by roughly 0.5-0.6% in people on injections (Beck et al., 2017; Lind et al., 2017). It works through visibility — you can’t fix what you can’t see. If you’re on the fence about a CGM, the trials are on your side.

References

  • Beck RW, 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. DOI: 10.1001/jama.2016.19975
  • Lind M, et al. Continuous Glucose Monitoring vs Conventional Therapy for Glycemic Control in Adults With Type 1 Diabetes Treated With Multiple Daily Insulin Injections: The GOLD Randomized Clinical Trial. JAMA. 2017. DOI: 10.1001/jama.2016.19976