Background <p>While type 2 diabetes (T2D) is preventable through lifestyle and medical interventions, identifying scalable and cost-effective strategies for population-level prevention remains a critical challenge. Wearable fitness trackers offer a resource-light approach by encouraging physical activity through real-time feedback. However, their cost-effectiveness compared to pharmaceuticals such as metformin remains underexplored in the UK context. This study aims to evaluate the cost-effectiveness of wearable fitness trackers versus metformin for T2D prevention among individuals with prediabetes.</p> Methods <p>We developed a Markov model to simulate two cohorts of prediabetic individuals, each receiving either fitness trackers or metformin, over a lifetime horizon with annual cycles. We conducted deterministic sensitivity analysis, scenario analyses and probabilistic sensitivity analysis (PSA) to further test the robustness of the results.</p> Results <p>In the base case, wearable fitness trackers were a dominant strategy, yielding higher quality-adjusted life years (QALYs) at lower costs than metformin. The incremental cost-effectiveness ratio (ICER) was–£4,451.70 per QALY, and the incremental net monetary benefit (NMB) was £3,722.07 at a willingness-to-pay threshold of £20,000 per QALY. Probabilistic sensitivity analysis (PSA) showed that wearable fitness trackers had a 94.8% probability of being cost-effective compared to metformin. In the worst-case scenario, wearable fitness trackers were dominated, with an ICER of–£3,632.13 per QALY and an incremental NMB of–£1,230.55.</p> Conclusions <p>Fitness trackers are a cost-effective and scalable option for T2D prevention in the UK, offering good value even under conservative assumptions. With appropriate implementation and support, they could play a valuable role in national prevention efforts.</p>