Who gets the biggest gains from CGM?
The people who benefit most are those with the worst glucose control at the start. In a study of 44 patients starting an implantable CGM, those who had never used CGM before (CGM-naïve) saw their HbA1c drop by 1.57 percentage points after 3 months, compared to a 0.53-point drop for people who had used a previous CGM [5]. Similarly, in a large real-world analysis of over 7,000 insured patients, the group with type 2 diabetes not on insulin—who often have less monitoring—saw a 0.9 percentage point HbA1c reduction after starting CGM [6]. The pattern is clear: the further you are from target, the more room for improvement, and CGM provides the data to make those improvements.
But benefit isn't automatic—it depends on actually using the device. The CGM TIME Trial, a randomized study in 144 children and teens starting insulin pump therapy, found that for every 100 hours of CGM use per 28-day period, HbA1c was 0.39 percentage points lower [7]. That means a child who wears the sensor 90% of the time will have meaningfully better glucose levels than one who wears it only half the time. Adherence matters as much as access.
Does CGM help people with type 2 diabetes as much as type 1?
Yes, and in some ways the benefits are even more striking for type 2 diabetes because the starting point is often worse. In a Medicaid population where cost was fully covered, people with type 2 diabetes who used CGM saw their HbA1c drop by 1.2 percentage points on average, and those who filled their prescriptions most consistently dropped by 1.4 points [2]. That's a bigger absolute improvement than many type 1 diabetes studies show, simply because type 2 patients often start with higher HbA1c levels. The same study found that CGM uptake and adherence were equally high across racial and ethnic groups once the financial barrier was removed, suggesting that cost—not willingness—is the main obstacle for underserved populations [2].
Even people with type 2 diabetes who don't use insulin benefit. In the large Aetna claims study, the subgroup with type 2 diabetes not on any insulin still achieved a 0.9 percentage point HbA1c reduction after starting CGM [6]. And in a UK national audit of over 18,000 adults, CGM use led to significant HbA1c reductions across all ethnic groups and all levels of socioeconomic deprivation, with the largest drops seen in the most deprived areas [8]. So CGM is not just for type 1 diabetes—it's broadly effective across the diabetes spectrum.
Are there special situations where CGM is especially valuable?
Pregnancy is one of the clearest examples. A systematic review and meta-analysis of randomized trials found that CGM use during pregnancy reduced the risk of having a large-for-gestational-age baby by about half (odds ratio 0.51) in type 1 diabetes, and a similar reduction was seen in gestational diabetes (odds ratio 0.46) [3]. The review also showed that CGM lowered HbA1c by 0.18–0.22 percentage points across pregnancy types. For a pregnant woman, avoiding a very large baby is a major clinical outcome, and CGM appears to help achieve that by keeping glucose more tightly in range.
Another high-stakes situation is fasting, such as during Ramadan. A study of 64 people with type 2 diabetes on insulin or sulfonylureas who fasted while using CGM found that those who achieved a pre-Ramadan time-in-range above 70% were much more likely to fast safely and successfully [4]. Those who succeeded had an average pre-Ramadan TIR of 84% versus only 55% for those who struggled. CGM allowed clinicians to identify high-risk individuals before fasting began, potentially preventing dangerous hypoglycemia or hyperglycemia. So CGM isn't just for day-to-day management—it's a tool for planning around specific life events.
About These Sources
This answer is built on 8 peer-reviewed studies — published from 2022 to 2026, 5 from 2024 or later, 4 in Q1 journals, collectively cited 196 times — selected as the most relevant from 15 studies that passed quality screening, drawn from 84 papers retrieved from a database of over 500 million.
Sources used in this answer
Intermittently Scanned Continuous Glucose Monitoring for Type 1 Diabetes
In a randomized controlled trial of 156 adults with type 1 diabetes and high HbA1c, intermittently scanned CGM with alarms lowered HbA1c by 0.5 percentage points more than fingerstick testing and added 130 minutes per day in target range.
Effect of CGM Access Expansion on Uptake Among Patients on Medicaid With Diabetes
In a retrospective cohort of 3,036 adults on Medicaid, CGM use was associated with a 1.2 percentage point HbA1c reduction in type 2 diabetes, with no significant differences by race/ethnicity when cost was fully covered.
Evidence for improved glucose metrics and perinatal outcomes with continuous glucose monitoring compared to self-monitoring in diabetes during pregnancy.
A systematic review and meta-analysis of randomized trials found that CGM use in pregnancy reduced HbA1c by 0.22 percentage points and halved the odds of large-for-gestational-age babies in type 1 diabetes and gestational diabetes.
1959-P: First Real-World Evaluation of CGM Outcomes during Ramadan Intermittent Fasting in Type 2 Diabetes Using the SYAI Sensor
In 64 high-risk adults with type 2 diabetes fasting during Ramadan, glycemic control worsened overall, but those with pre-Ramadan time-in-range above 70% were significantly more likely to fast safely and successfully.
1965-P: Glycemic Outcomes in CGM-Naïve vs. Experienced Patients Using Implantable CGM
In a 14-month study of 44 diabetic patients starting an implantable CGM, CGM-naïve patients achieved a 1.57 percentage point HbA1c reduction at 3 months, compared to 0.53 points for those switching from a previous CGM.
Initiating continuous glucose monitoring is associated with improvements in glycemic control and reduced health care resource utilization for people with diabetes in a large US-insured population: A real-world evidence study
In a real-world study of 7,336 insured patients, CGM initiation was associated with a 0.7 percentage point HbA1c reduction overall and a 0.9 point reduction in type 2 diabetes not on insulin, plus a 67% reduction in diabetes-related hospitalizations.
Timing of CGM initiation in pediatric diabetes: The CGM TIME Trial.
In a randomized trial of 144 children and teens starting insulin pump therapy, initiating CGM at the same time as the pump led to higher CGM adherence, and each additional 100 hours of CGM use per month was linked to a 0.39 percentage point lower HbA1c.
Exploring the interaction between ethnicity, deprivation and the use of CGM on diabetes outcomes-A study from the Association of British Clinical Diabetologists.
In a UK national audit of 18,139 adults with diabetes, CGM use led to significant HbA1c reductions across all ethnic groups and all levels of deprivation, with the largest reductions in the most deprived areas.