BackgroundThe Women's Wellness with Type 2 Diabetes Programme (WWDP) is an online behavioural intervention for midlife women living with type 2 diabetes. The gender-specific intervention fosters self-efficacy, encouraging positive wellbeing behaviours to enhance diabetes and menopause outcomes. In 2016, We co-led a feasibility trial and process evaluation with 70 women aged 45–50 years from the UK and Australia. The intervention comprised an e-book, a website, and nurse consultations. The WWDP seemed to improved diabetes distress, self-efficacy, and menopausal symptoms, but with impactful, costly, diabetes nurse input, compromising feasibility and delivery by the NHS. We report WWDP refinement using the 2021 Medical Research Council (MRC) framework for complex interventions to optimise future implementation. MethodsIntervention refinement was guided by six core MRC elements of context, programme theory, stakeholder engagement, key uncertainties, intervention refinement, and economic considerations. Critical analysis of quantitative and qualitative feasibility data, informed by self-efficacy theory, provided a deeper understanding of how the intervention was used. Eight PPI consultations took place between Sept 1, 2021, and Dec 31, 2022, with three women from diverse cultural and socioeconomic backgrounds and three female diabetes professionals to strengthen the e-book and methods of support for women undertaking the programme. FindingsContext was improved by the feasibility study and the PPI consultations, making the e-book relevant to UK health care. Understanding that self-efficacy was supported through primary use of peer group, and goal setting components supported the existing programme theory. Stakeholder engagement shaped the structure of the online peer support group. The feasibility study revealed uncertainties around goal settings. These uncertainties were addressed by introducing individualised goals focusing on aspects like medication adherence. The nurse support in the intervention was replaced with peer support, which might lead to greater economic feasibility of the programme. An optimised website and individualised goal setting underpin the WWDP. InterpretationThe MRC Framework provides intervention refinement structure, allowing adaptive adjustments based on emerging evidence, feedback, and contextual nuances. Limitations exist. Intervention refinements, including peer support, might affect adherence and unexpected interactions. New components could influence long-term efficacy. FundingTurkish Ministry of National Education.