Standard operating procedures (SOPs) are a part of healthcare operations but relying on explicit knowledge is not necessarily sufficient to continuously adapt and improve processes. The theory of communities of practice (CoP) proposes an approach to knowledge sharing that could supplement the use of SOPs. A CoP is a social community formed around a practice (e.g. ICU nursing) which induce a propensity to share experiences and thereby constitute knowledge sharing (Lave & Wenger 1991; Brown & Duguid 1991). CoP was conceived as a descriptive construct but has gained popularity and is found to improve practice performance, but knowledge about developing and measuring CoP is lacking (McKellar et al. 2014; Li et al. 2009a; Ison et al. 2014). We propose a method to develop a CoP and the method is tested in a blood analysis unit at ‘Nordsjællands Hospital’ in Denmark. The interventions were identified from current CoP research. Interventions were initiated just after baseline measurement. The following interventions took place: The practice was operationalized narrowly as employees performing a specific operational task. The practice was chosen due to a high frequency and recurring problems. A voluntary CoP coordinator was identified. She then invited her colleagues to participate in the CoP and arranged CoP meetings. The ‘Event Effect Method’ was used to control for effect modifiers by identifying events both part and not part of the intervention and estimating their effect on CoP. The development method improved knowledge sharing and the SOP. The method confirmed some earlier findings regarding CoP development and raises new questions regarding participant engagement, researcher role and start-up workshop. The results indicate that knowledge sharing within operations can be improved by considering tacit and explicit knowledge sharing as supplementary.