OBJECTIVES: Even though Islam excludes the sick from Ramadan Fasting (RF), countless Muslims choose to fast throughout this holy month. So, it is of paramount importance to review how RF influences patients with chronic Heart Failure with reduced Ejection Fraction (HFrEF). Our study intended to check the safety of RF in these patients. METHODS: We selected patients under 75 years old with compensated chronic HFrEF. After applying all the exclusion conditions, those who insisted on fasting during the coming Ramadan were enrolled in fasting Group I (90 patients). Those who decided not to fast were listed as control Group II (68 patients) to ensure a comprehensive model. RESULTS: Patients with prior revascularization, AF, lower e-GFR, and poor functional capacity (higher NYHA class) had higher AEs after RF with P values (0.013, 0.027, 0.001, and 0.038), respectively. The low e-GFR and prior revascularization were independent predictors of AEs with P-values (0.005 & 0.031), respectively. The e-GFR (50 ml/min/1.73 m CONCLUSIONS: RF may be harmless in low-risk patients with chronic HFrEF under the supervision of a medical professional. However, HFrEF patients with prior coronary revascularization or CKD may have a higher incidence of AEs.