Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.135.

The Prophet, upon whom be peace, was cupped while he was fasting. However, if doing this weakens the fasting person, it is disliked. Thabit al-Bunani asked Anas: “Did you dislike cupping for a fasting person during the time of the Prophet?” He answered: “No [we did not], unless it made someone weak.” This is related by al-Bukhari and others. Vivisection follows the same ruling as cupping.