Ramadan represents the fourth of the five pillars of the Islamic creed. Although patients are exempted from observing this duty, they may be eager to share this moment of the year with their peers. However, there are no guidelines that can help physicians to address the concerns of patients with infectious diseases fasting during Ramadan. For this purpose, we performed a systematic review. of 51 articles. Our main findings are that: 1) patients suffering from diabetes at risk of developing infectious complications should not fast; 2) Ramadan fasting has little impact on diarrheal patients; 3) HIV represents a challenge, and ad hoc drug combinations should be recommended to patients, and the patients should be advised not to take fatty meals that could interfere with the treatment; 4) Ramadan has no effect on the effectiveness of anti-helminthic therapy; and 5) patients with active ulcers should not fast, as they have a higher probability of developing complications.