Objectives To (1) assess the hydration knowledge, attitudes and practices (KAP) of doctors; (2) develop an evidence-based training package; and (3) evaluate the impact of the training package. Design Educational intervention with impact evaluation. Setting Cambridgeshire, UK. Participants General practitioners (GPs (primary care physicians)). Interventions Hydration and healthcare training. Main outcome measures Hydration KAP score before and immediately after the training session. Results Knowledge gaps of doctors identified before the teaching were the definition of dehydration, European Food Safety Authority water intake recommendations, water content of the human body and proportion of water from food and drink. A face-to-face teaching package was developed on findings from the KAP survey and literature search. 54 questionnaires were completed before and immediately after two training sessions with GPs. Following the training, total hydration KAP scores increased significantly (p<0.001; median (25th, 75th centiles); 32 (29, 34)). Attendees rated the session as excellent or good (90%) and reported the training was likely to influence their professional practice (100%). Conclusions The training package will continue to be developed and adapted, with increased focus on follow-up strategies as well as integration into medical curricula and standards of practice. However, further research is required in the area of hydration care to allow policymakers to incorporate hydration awareness and care with greater precision in local and national policies.