Theory and practice: definition of clinical practice guidelines Guidelines can be understood as tools to support clinical decision making. In its 2011 standard reference work, ‘Clinical practice guidelines we can trust’, the US Institute of Medicine (2011) states: ‘Rather than dictating a one-size-fits-all approach to patient care, [clinical practice guidelines] should aid clinician and patient decision-making by clearly describing and appraising the evidence and reasoning regarding the likely benefits and harms related to specific clinical recommendations.’ SDM is a key element of the clinical encounter as reflected in patients’ views. Its importance, and the need for input from healthcare professionals (HCPs) when making a treatment choice, were recurrent findings in DECIDE research (Fearns et al. 2016). The Institute of Medicine’s definition emphasises that guidelines can support HCPs in guiding patients through the SDM process. However, some considerations and insights from guideline research suggest that clinicians’ misconception of the underlying evidence, the format of many guidelines, and the wording of their recommendations might be a barrier to individual SDM: Evidence from a large sample of various guideline groups and a review of qualitative evidence (Carlsen et al. 2007) suggest that some clinicians may misinterpret guideline recommendations as absolute do’s or don’ts that are opposed to SDM. This seems to apply especially to recommendations in favour of interventions.The development of guideline-based performance measures and pay-for-performance models may plausibly lead to clinicians following recommendations rather than discussing options with their patients, especially when these impact on either certificates or reimbursement (Legaré and Witteman 2013). The same may apply to the increasing role that guidelines have in legal contexts, that is, malpractice claims (Mackey and Liang 2011).A survey among physicians indicated that stronger and weaker guideline recommendations may be perceived as equally binding (Nast et al. 2013).In the literature, guidelines have been largely criticised for not providing guidance for individual situations that may need to go beyond the generalisation of a given guideline recommendation. This may be especially so when patients have comorbidities or multimorbidity (Elwyn et al. 2016; Young et al. 2015). Key to success: harmonising guidelines with SDM Guidelines, in a widely cited definition (Institute of Medicine 2011), are described as facilitators of clinical decision making. However, their potential to impede patient-centred decision making has to be taken into account. In their Guidance manual, the German Association of the Scientific Medical Societies addressed this issue by explicitly stating: ‘Guidelines can be understood as “treatment and decision corridors” which can or should be deviated from in justified cases. The applicability of a guideline or individual guideline recommendations should be reviewed in individual situations in the individual encounter according to the principles of shared decision-making.’ (German Association of the Scientific Medical Societies 2012) Therefore, guideline adherence truly means meticulously considering whether to deviate from a recommendation in the care of an individual person and discussing this with them (Kühlein and Schaefer 2020). To support clinicians in doing so, it is most important to integrate tools and elements into the guideline that facilitate talking about these options and SDM. This is why guidelines and decision tools have been stated as maintaining an ‘inevitable relationship’ (van der Weijden et al. 2012). Such a relationship seems crucial, because the format of many guidelines does not provide even basic elements that enable HCPs to present options and their probabilities to patients (Morgott et al. 2019). The patients’ view seems to support this. Qualitative evidence from the DECIDE project indicated that patients need health information that enables them to choose between treatment options, including information about harms (Fearns et al. 2016). They would like help with making such choices from HCPs, especially general practitioners. Hence, guidelines have an important role here because they are mainly aimed at HCPs. The following sections provide some guidance about different tools and strategies guideline that developers may use to enable and support SDM through guidelines.