Fasting is one of the important rituals in Islam. According to the Islamic faith, it is an obligation for all Muslims. It is also a common practice in other religions such as Christianity, Judaism, and Hinduism and for philosophies such as Buddhism, Taoism, and Jainism. Each belief or sect has a different type of fasting according to their creed. The fasting period and practice may differ. For example, the Ramadan for Sunni Muslims, Muharram for Alevi Muslims and Lent for Catholics are specific periods for fasting. Ramadan fasting lasts for 29–30 days, Muharram fasting for 10–12 days, and Lent fasting lasts for 40 days. The Ramadan fasting period may vary with the geographic region, but generally it is 12 hours long. It can be as long as 22 hours in the polar regions during summertime (1–4). The practice of fasting in Islam is a mandatory ritual for every healthy individuals, but fasting is be optional for those who are too sick to fast. But what sickness permits breaking the fast is not clear. Therefore, the eligibility or the lack of it to fast is steeped in controversy for some sick people. Particularly in the last 2 decades, numerous studies have been published regarding the effects of religious fasting on general health. More than 1000 articles are available on the PubMed database related to Ramadan and Lent/Biblical fasting. However, there is limited evidence for this topic, and most studies are retrospective with a limited number of patients. Moreover, in general, the quality is poor with limited conclusions to draw suggestions for clinical practice (5, 6). Furthermore, it is impossible to conduct randomized controlled trials on religious fasting to reach more conclusive results. The main objective of the current paper is to summarize the current literature on Ramadan fasting and discuss the potential beneficial or adverse effects on patients with or at risk of cardiovascular disease. The second aim is to propose an evidence-based suggestion regarding who is eligible and not eligible for fasting. Specific highlights and consideration for each patient group are discussed in following sections and summarized in Table 1. Table 1 Consensus statements on Ramadan fasting in patients with cardiovascular diseases