Adherence to medication, commonly reported as being 50% in chronic diseases, is of great concern in healthcare. Medication non-adherence is particularly apparent in chronic diseases, where treatment is often preventative and may provide little or no symptomatic relief or feedback for the patient. A lot of research has been undertaken to describe the extent of non-adherence to long-term anticoagulation therapy, particularly with vitamin K antagonists and more recently with direct oral anticoagulants. However, the literature is scarce with respect to describing adherence to anticoagulation in terms of the behavioural aspects that influence medicine use. Utilizing the COM-B (capability, opportunity, motivation and behaviour) psychological model of non-adherence, we present the available evidence, not only in terms of describing the extent of the non-adherence problem, but also describing why patients do not adhere, offering theory-driven and evidence-based solutions to improve long-term adherence to chronic anticoagulation therapy. Lessons learned are not only applicable within the field of anticoagulation but throughout haematology.