Background Glycated haemoglobin (HbA1c) targets are commonly used to guide patient management in diabetes to reduce future risk of diabetes complications, but little is known of the psychological impact of HbA1c target-setting. We explored the feasibility of undertaking a conclusive study evaluating the impact of setting explicit HbA1c targets in adults with diabetes. Methods A randomised, mixed-methods study design was used to quantitatively and qualitatively evaluate the psychometric and biomedical impact of intensified or relaxed glycaemic targets in adults with diabetes. Alongside baseline measurement of HbA1c, blood pressure and body mass index, patients completed baseline validated psychometric questionnaires (EuroQoL-5D-5L, Problem Areas In Diabetes, Summary of Diabetes Self-Care Activities, Well-Being Quetionnaire-12, Diabetes Empowerment Scale-Long Form) and were randomised 1:1. Participants in group A received explicit HbA1c target intervention targets 5 mmol/mol above current HbA1c. Participants in group B received explicit HbA1c targets 5 mmol/mol below current HbA1c. Rates of eligibility, recruitment, retention and questionnaire response were recorded. Outcomes were re-measured 3-months post-intervention. Patients and healthcare professionals attended semi-structured interviews for qualitative evaluation. Results Fifty participants were recruited. Withdrawal rate was 34% (n=17). Endpoint evaluation revealed no significant between-group differences in patient-reported outcome measures or HbA1c levels. Overall, levels of distress (-4.4, p=.009), self-efficacy (.25 [.09–.41], p=.004) and subsequent HbA1c readings (-2.8 [-5.0–-.7], p=.012) improved, with non-significant changes seen in health-related quality of life, wellbeing, and self-care. Patients and healthcare professional interviews demonstrated study acceptability alongside specific motivators (e.g., target achievability, hypoglycaemia avoidance) and demotivators (e.g., lack of understanding, lack of target achievability) for striving to reach glycaemic targets. Combined qualitative data from patient and healthcare professional interviews and quantitative study aspects triangulated, enhancing data trustworthiness, and informing future hypotheses and methodologies. Discussion This mixed-methods study demonstrates feasibility and provides a novel insight into the psychological implications of HbA1c target-setting. Trial registration The study is registered with the ISRCTN (registration number: 12461724; date registered: 11th June 2021).

The authors have declared no competing interest.

ISRCTN 12461724

https://doi.org/10.1371/journal.pone.0275980

The author(s) received no specific funding for this work.

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The study received ethical approval from the UK Health Research Authority (Cornwall and Plymouth Research Ethics Committee, REC reference 21/SW/0043, IRAS ID: 291254, 30th April 2021, see supporting information S2)

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