Background: β-thalassemia major (β-TM) is an inherited autosomal recessive disorder manifested by the hemoglobin β chain synthesis alteration. It is a lifelong illness with a scope of a wide range of complications. Many kinds of literature evaluated the effect of Ramadan intermittent fasting (RIF) on different medical conditions. However, there are no precise guidelines regarding its effect on patients with β-TM.Methods: A retrospective cohort study was conducted on β-TM patients who visited the hereditary blood disorder center at Al Karama Teaching Hospital in Baghdad. Accordingly, six parameters were used to evaluate the effect of RIF on β-TM patients before, during, and after Ramadan. These parameters include hemoglobin level, frequency of transfusion, aspartate aminotransferase (AST) level, alanine aminotransferase (ALT) level, left ventricular ejection fraction % (EF%), and spleen size. All of these details, including the demographic characteristics of age, gender, history of splenectomy, and body mass index (BMI) were retrieved from the patient's medical records after confirming their fasting through one-to-one interviews. This study aimed to fill the gap and investigate the possible effect of RIF on the severity of β-TM.Results: A total of 184 β-TM patients were enrolled in this study. The mean duration of fasting was 25.2±2.18 days. More than half (110) of the patients were females (59.8%). Whereas, the mean age was 24.8±3.5 years. One-third of the patients (65) had a splenectomy (35.3%) and more than two-thirds had normal BMI. The initial parameters used to score the severity of β-TM were evaluated separately. As a result, the hemoglobin level remained steady without any statistical significance during the three months. In addition, the frequency of blood transfusion and the spleen size carried the same result. Although the lowest median and range of liver enzymes were recorded during Ramadan, they were statistically insignificant compared to pre and post-fasting. Moreover, the left ventricular EF% was insignificant regardless of the patient's history of heart disease.Conclusion: This study revealed that RIF does not seem to affect the severity of β-TM if the patients proceed with fasting. However, further studies in more countries with a bigger sample size are recommended to confirm these findings.