Continuous glucose monitoring versus self-monitoring of
blood glucose in individuals with type 2 diabetes:
a randomised, multicentre, open-label, superiority trial
Emma G Wilmot, Patrick Moore, Thozhukat Sathyapalan, Pratik Choudhary, Jonathan Z M Lim, Sankalpa Neupane, Thomas S J Crabtree,
Ahmed Iqbal, Mark L Evans, Gerry Rayman, Hermione C Price, Ramzi A Ajjan, Yee S Cheah, Alistair Lumb, Samiul Mostafa, Iqbal Malik,
Iain Cranston, Thinzar Min, Edward B Jude, Shivshankar Seechurn, James McLaren, Katharine Barnard-Kelly, Thomas Yates, Rachel A Elliott,
Lalantha Leelarathna, on behalf of the FreeDM2 Study Group*
Summary
Background Type 2 diabetes is the most common metabolic disorder worldwide, accounting for about 90% of people
living with diabetes. Glycated haemoglobin (HbA1c), a measure of chronic glycaemic exposure, correlates with the risk
of long-term complications, which can result in substantial morbidity for people with diabetes and major costs to
health-care systems. The value of continuous glucose monitoring (CGM) in people with type 2 diabetes managed with
basal insulin and modern therapies remains unclear. FreeDM2 aimed to evaluate the effectiveness of real-time CGM
in adults with type 2 diabetes.
Methods
This open-label, parallel-design, randomised controlled trial conducted across 24 primary and secondary
care centres in the UK enrolled adults with type 2 diabetes managed with basal insulin and SGLT2 inhibitors or GLP-1
receptor agonists or dual GIP/GLP-1 receptor agonists with HbA1c 7·5–11·0%. Participants were assigned (2:1; using
permuted block randomisation by study site, generated by Sealed Envelope) to CGM (intervention) or continuation of
self-monitoring of blood glucose (SMBG; control), across two phases: weeks 1–16, self-management with basal insulin
self-titration; and weeks 17–32, clinician-supported where additional therapies could be initiated in line with national
guidance. Participants and study site staff were not masked to group allocation. The primary outcome was difference
between groups in HbA 1c concentrations at 16 weeks, and the key secondary outcome was the difference between
groups at 32 weeks, both in the treatment policy estimand. Safety analysis included all randomly assigned participants.
The FreeDM2 randomised controlled trial is registered at ClinicalTrials.gov (NCT05944432) and is complete.
Findings
Between July 26, 2023, and Jan 31, 2025, 469 individuals underwent screening for potential study inclusion,
140 were excluded due to not meeting inclusion criteria, and 329 were included in the baseline phase of the study.
26 individuals were then excluded due to insufficient data capture or withdrawal, and 303 participants were randomly
assigned; 198 to the CGM intervention group and 105 to the SMBG control group. 204 (67%) participants were male
and 99 (33%) were female, the mean age of the cohort was 60·7 years (SD 9·8), and mean diabetes duration was
16·7 years (6·9). Baseline HbA 1c concentration was 8·8% (SD 1·0) in the CGM group and 8·8% (1·1) in the control
group, decreasing to 8·0% (0·9) in the CGM group and to 8·7% (1·1) in the control group at week 16 (adjusted
difference −0·6 [95% CI −0·8 to −0·3]; p<0·0001) and decreasing further to 7·8% (0·9) in the CGM group and to
8·3% (1·2) in the control group at week 32 (adjusted difference −0·5 [95% CI −0·7 to −0·2]; p<0·0001). There was a
similar incidence of non-device-related adverse events in both groups, and two instances of severe hypoglycaemia in
the control group.
Interpretation
In adults with type 2 diabetes on basal insulin plus modern therapies, real-time CGM improved
glycaemic control versus SMBG during self-management and under clinician-supported managemen
Research in context
• Evidence before this study
We searched PubMed on Jan 13, 2023, using combinations of the
terms “type 2 diabetes”, “continuous glucose monitoring”,
“randomised trial”, “basal insulin” with Boolean operators and
selecting English language only. We repeated the search on
Dec 8, 2025.
These searches identified one relevant randomised
study that provided evidence for the use of real-time continuous
glucose monitoring (CGM) in adults with type 2 diabetes treated
with a basal-only insulin regimen. The MOBILE study
demonstrated an adjusted difference in glycated haemoglobin
of −0·4% at 8 months compared with self-monitoring of blood
glucose (SMBG).
However, high-quality evidence for the
effectiveness of CGM in individuals using basal insulin combined
with newer agents, such as SGLT2 inhibitors or GLP-1 or dual GIP/
GLP-1 receptor agonists, is scarce; for example, in the MOBILE
trial, only 27% of participants met this definition. There was also
a lack of evidence for the behavioural mechanisms through
which CGM supports glycaemic management in adults with
type 2 diabetes.
• Added value of this study
FreeDM2 is one of the largest trials evaluating real-time CGM
against SMBG in adults with type 2 diabetes treated with basal
insulin and newer agents, including SGLT2 inhibitors and GLP-1
or dual GIP/GLP-1 receptor agonists. It features a unique
two-phase design to assess the effect of self-management and
clinician-supported changes in management.
The trial and
recruitment strategy were designed to be as representative as
possible of real-world clinical practice and patient populations,
and the high proportion of participants using SGLT2 inhibitors
or GLP-1 or dual GIP/GLP-1 receptor agonists reflects recent
advances in diabetes management.
We found that real-time
CGM led to significant improvements in glycaemic outcomes
compared with SMBG, without increasing hypoglycaemia or
other serious adverse events. Improvements in glycaemia were
observed during the self-management phase, despite no
between-group differences in insulin doses, suggesting that
benefits were driven by lifestyle changes. Evaluation of activity
levels and patient-reported outcomes indicates that those
using real-time CGM were more active and made healthier
dietary choices than participants practising SMBG. Subsequent
transition to clinician-supported management with escalation
of therapies to improve glycaemia in both trial arms led to
improved glycaemia in both groups, but between-group
differences in glycaemia persisted.
• Implications of all the available evidence
The FreeDM2 trial provides robust evidence that real-time CGM
statistically and clinically significantly improves glycaemic
control in people with type 2 diabetes and suboptimal glucose
concentrations, despite treatment with basal insulin, SGLT2
inhibitors, GLP-1 receptor agonists, or dual GIP/GLP-1 receptor
agonists. Improvements were achieved through self-
management and sustained after clinician intervention with
additional therapies.
This randomised controlled trial
establishes the utility of real-time CGM in the management of
type 2 diabetes and provides rationale for updating treatment
guidelines to support wider use of the technology.
From the article
Discussion
In this randomised trial, use of real-time CGM resulted
in improved HbA1c concentrations in participants with
type 2 diabetes treated with basal insulin and SGLT2
inhibitors or GLP-1 or dual GIP/GLP-1 receptor agonists,
without increasing hypoglycaemia or other serious
adverse events. The study enrolled a population
commonly encountered in routine clinical practice, in
which glycaemic targets are not achieved despite
contemporary therapy, highlighting the challenges of
managing type 2 diabetes as the condition progresses
over time. 25
The FreeDM2 trial has demonstrated the role
of CGM in supporting improved glycaemic control
through enhanced self-management and more informed
pharmacological optimisation.
The study was powered to detect a 0·35 percentage
point difference in HbA1c concentration between groups;
therefore, the observed difference of 0·6 percentage
points (95% CI −0·8 to −0·3) exceeded the threshold for
clinical significance established in current guidelines.26
Participants using real-time CGM also recorded higher
time in the target glucose range (3·9 to 10·0 mmol/L)
and lower mean glucose concentrations throughout
compared with the control group, as well as being more
likely to achieve HbA1c targets. Furthermore, CGM users
reported improved participant-reported outcomes,
including satisfaction with glucose monitoring and
confidence in management of hypoglycaemia;
accordingly, use of glucose sensors was high, with a
median sensor usage of 97·6% in the first phase of the
study and 98·2% in the second phase of the study. These
findings support recent consensus recommendations
which highlight the role of CGM in person-centred
diabetes care for type 2 diabetes beyond glycaemic indices
alone.27
The MOBILE trial also enrolled participants with
type 2 diabetes treated with basal insulin but with a
lower proportion receiving treatment with SGLT2
inhibitors or GLP-1 or dual GIP/GLP-1 receptor agonists
(27% compared with 95% in the present study). 12 The
participants using CGM recorded a decrease in HbA 1c
concentrations at 8 months (adjusted mean difference
−0·4 percentage points [95% CI −0·8 to −0·1]). Unlike
the present study, MOBILE did not have a self-
management phase and included several clinic visits
during the first 16 weeks while also permitting therapy
changes directed by a study clinician throughout. 12
The effectiveness of CGM has been hypothesised to
result from a combination of lifestyle, diet, and treatment
optimisation.28 A unique feature of FreeDM2 is its
two-phase design allowing assessment of the effect of the
use of real-time CGM on lifestyle factors and basal insulin
optimisation before intervening with additional therapies.
During the participant-managed phase, the 0·6 percentage
point (95% CI −0·8 to −0·3; p<0·0001) between-group
difference in HbA1c concentration was achieved with no
between-group difference in insulin doses or non-insulin
medication changes, suggesting that the glycaemic
benefits might have been driven through lifestyle changes.
An exploratory analysis of the MOBILE study showed no
significant between-group differences in total daily insulin
dose or changes to non-insulin medications.12 In FreeDM2,
at 16 weeks, there was a small but clinically meaningful
between-group difference in total physical activity,29 along
with improvements in diet quality; however, these
between-group differences were not sustained at 32 weeks.
Accordingly, real-time feedback of glucose concentrations
through CGM during self-management might help people
with type 2 diabetes make healthier lifestyle choices. The
steep early rise in time in range after CGM initiation also
suggests a rapid response to real-time glucose feedback,
driving early adjustments in self-management behaviours,
a pattern that mirrors observations from an exploratory
analysis of the MOBILE study.30 Therefore the degree to
which small changes in lifestyle behaviours can mediate
early improvements in glycaemic control in response to
CGM initiation warrants further investigation.
When participants transitioned to clinician-supported
care with escalation of therapies to further improve
glycaemia, the between-group difference in HbA1c
concentrations persisted. Availability of CGM data led to
a 4-fold greater clinician-initiated prandial insulin use,
probably reflecting enhanced recognition of post-prandial
glucose excursions through direct glucose visualisation.
Notably, there were no between-group differences in the
addition of GLP-1 agonists nor any difference in body
weight or blood pressure. Throughout the study,
participants using CGM were more satisfied with their
glucose monitoring device and had increased confidence
in avoiding hypoglycaemia.
Together with previous randomised evidence, findings
from this study support the use of CGM for people with
type 2 diabetes treated with basal insulin in routine
practice. A dedicated health economic analysis based on
this study will further inform clinical and policy decision
making. Strengths of FreeDM2 include its unique
two-phase design which allowed a new understanding of
the effect of self-management and clinician support.
Moreover, trial conduct was aimed at being as
representative of real-world practice as possible, with only
a single follow-up visit in the first phase of the study. The
trial population was recruited from primary and
secondary care and a diverse socioeconomic background.
The FreeDM2 study allowed complete remote
participation, including participants who might not
otherwise join due to the need for hospital or research
facility visits. The higher baseline use of SGLT2 inhibitors
and GLP-1 receptor agonists reflects recent advances in
diabetes management and helps address gaps in the
existing evidence.
Limitations include the open label design of the study,
which is necessitated by the nature of the device. The
effect of a global shortage of GLP-1 receptor agonists
during the study led to restrictions on prescribing these
drugs in the UK, thereby prolonging recruitment.
Despite evaluating several secondary outcomes to
identify factors influencing glycaemia, no single factor
accounted for the magnitude of glycaemic improvement
observed. The available tools might have lacked sufficient
sensitivity to detect subtle lifestyle changes, such as
timings or meal portion sizes. Future studies
incorporating more sensitive and granular measures,
such as detailed dietary diaries and continuous physical
activity monitoring, might help to better characterise the
mediators of benefit and optimise CGM use in this
population. Furthermore, at the end of the trial, 20% of
participants in the CGM group reached the recommended
HbA 1c target of less than 7%, with no plateau in
improvement observed, suggesting potential for further
optimisation and residual unmet need. Further research
is therefore warranted to understand the longer-term
effect of CGM on glycaemia.
In conclusion, in this study, CGM supported
statistically and clinically significant improvements in
glycaemic control compared with SMBG, with no safety
concerns, in people with type 2 diabetes and suboptimal
HbA 1c concentrations already on treatment with basal
insulin and SGLT2 inhibitors or GLP-1 or dual GIP/
GLP-1 receptor agonists. These improvements were
achieved through self-management and sustained during
clinician-supported management including use of
additional therapies. Findings from this study support
the utility of CGM for people with type 2 diabetes treated
with bas
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Nyhetsinfo
Utifrån denna studie publicerad i Lancet April 26 och i enlighet med ADA evidensgrad A,
har SFD i skriften Mål och målsättning diabetes vuxna 2026 på sid 12 under Glykemisk kontroll vid T2DM,
uppdaterat texten så att det tagits bort ”basalinsulinbehandling” och nu står enbart insulinbehandling, dvs
CGM bör erbjudas vid T2DM vid insulinbehandling, som inte uppnår sitt glykemiska mål utan hypoglykemier
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Läs också nedaqn debattinlägg
CGM kan ändra liv vid T2DM – varför når tekniken inte fler? Debattinlägg
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