Last updated July 18, 2026
Key finding
The between-treatment differences in HbA1c of 0.4% was not significant (p = 0.903).
This study evaluated the impact of adjunctive metformin therapy on glycemic control in overweight/obese youth with type 1 diabetes, finding no significant differences in key outcomes.
Quick read
The essential study design details in one scan.
EvidenceScore™
Moderate
Study type
RCTs
Follow-up
Extended (5–20+ y)
Risk of bias
Some Concerns
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Plain-language summary
A plain-language read of the study’s main message and where it applies.
Study focus
This study evaluated the impact of adjunctive metformin therapy on glycemic control in overweight/obese youth with type 1 diabetes, finding no significant differences in key outcomes.
Understanding the effectiveness of adjunctive therapies like metformin is crucial for managing type 1 diabetes in youth, especially those who are overweight or obese. These findings suggest that metformin may not provide additional benefits in glycemic control for this population, guiding clinicians in treatment decisions and patient management.
Small sample size may limit generalizability Short duration of the study may not capture long-term effects Potential unmeasured confounders affecting outcomes
Published in
Publication details and source links for this paper.
Benjamin UN, Louise M, Karen C, et al. Adjunctive Metformin Therapy Improves Glycemic Control in Overweight/Obese Youth with Type 1 Diabetes: A Randomized Controlled Trial. PLOS ONE. 2015;10(9):e0137525. doi:10.1371/journal.pone.0137525
No significant change in HbA1c (0.4%, p = 0.903)
Non-significant reduction in fasting plasma glucose (-18.9 mg/dL, p = 0.927)
No significant change in total daily dose of insulin (p = 0.936)
Evidence network
Understand where this research contributes within the broader evidence network.
This study contributes evidence to Metformin and Fasting Plasma Glucose (FPG), HbA1c, Total daily insulin dose.
This study contributes evidence to
Primary intervention
Metformin
Primary outcomes
Primary intervention
Primary outcomes
Intervention and outcome relationships this study adds to the evidence network.
Editorial context
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Evidence network role
This section describes how the study fits into the current evidence network. It does not determine whether an intervention works on its own.
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Primary evidence
Evidence relationship
Related evidence
Evidence relationship
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Evidence relationship
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Core evidence
The primary outcomes reported in this study.
Metformin → Fasting Plasma Glucose (FPG)
Metformin → Fasting Plasma Glucose (FPG)
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Relationships organized using the Dediabetes Evidence Intelligence™ framework.
This study contributes to evidence on Metformin Therapies and HbA1c, Metformin Therapies and Fasting Glucose.
This study contributes to the evidence on the following intervention-outcome relationships.
Medications
Medications
Curated evidence collections and hubs this study is part of.
All studies measuring HbA1c
Measures HbA1c as a key outcome.
All studies on Metformin Therapies
Contributes to Metformin Therapies evidence base.
All studies measuring Fasting Glucose
Measures Fasting Glucose as a key outcome.
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11 results
5 results
11 results
11 results
5 results
Generated from the study's connected evidence using Evidence Intelligence™.
Metformin Therapies may improve Fasting Glucose.
ConsistencyScore™: Results are generally consistent across studies.
Ranked evidence signals
Fasting Plasma Glucose (FPG)
EvidenceScore™ Strong | EvidenceScore™ 83.2 | strong positive | ConsistencyScore™ Consistent | 1 study
Why this answer: This answer is based on 8 supporting studies with generally consistent results and a positive effect signal.
Limitations
Metformin Therapies appears to improve HbA1c.
ConsistencyScore™: Results are generally consistent across studies.
Ranked evidence signals
HbA1c
EvidenceScore™ Strong | EvidenceScore™ 85.2 | moderate positive | ConsistencyScore™ Generally Consistent | 1 study
Why this answer: This answer is based on 13 supporting studies with generally consistent results and a positive effect signal.
Limitations
Metformin Therapies may improve Insulin Resistance.
ConsistencyScore™: Results are generally consistent across studies.
Ranked evidence signals
Total daily insulin dose
EvidenceScore™ Strong | EvidenceScore™ 79.0 | weak positive | ConsistencyScore™ Generally Consistent | 1 study
Why this answer: This answer is based on 6 supporting studies with generally consistent results and a positive effect signal.
Limitations
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