The justification of anticoagulant therapy is assessed in relation to the patient's individual risk of stroke using the CHA2DS2-VASc risk score. In high-risk patients (CHA2DS2-VASc ≥ 2), anticoagulant therapy (direct anticoagulant or warfarin) is indicated almost without exception. In patients with moderate risk (CHA2DS2-VASc = 1), the need for anticoagulation is assessed individually. Anticoagulation may be omitted, if the bleeding risk is high, the patient does not want to use anticoagulant therapy, the risk factor (e.g. hypertension) is well managed and the patient does not have other, smaller risk factors (e.g. smoking, dyslipidaemia, renal failure). Anticoagulation therapy is not given to low-risk patients (CHA2DS2-VASc = 0), since in such patients its adverse effects exceed its benefits. ASA and ADP receptor antagonists are not suitable for the prevention of thrombosis associated with atrial fibrillation, due to their poor efficacy and adverse effects. The NNT (number needed to treat) indicates the number of patients that need to be treated so that one of them avoids stroke during one year, compared with those using placebo. If needed, the anticoagulation therapy may be temporarily discontinued during such procedures or surgery that entail bleeding risk, with the exception of highest-risk patients.