It is suggested that Hijamah is practiced on the ‘odd’ days of the Lunar Calendar. Further to this, the specifically recommended days are Monday, Tuesday & Thursday. The optimum Sunnah days to perform Hijamah Therapy are the 17th, 19th and 21st days of the Lunar Calendar providing these days coincide with Monday, Tuesday and Thursday. The Prophet (peace & blessings of Allah be upon him) advised against practicing Hijamah on Friday, Saturday and Sunday and very strongly advised against practicing Hijamah on Wednesdays.
Ibn Umar (may Allah be pleased with him) reported that the Messenger (saw) said, “Hijamah on an empty stomach is best. In it are a cure and a Blessing. It improves the intellect and the memory. So use Hijamah with the Blessing of Allah on Thursday. Keep away from Hijamah on Wednesday, Friday, Saturday and Sunday to be safe. Perform hijamah on Monday and Tuesday for it is the day that Allah saved Ayub from the trial. He was inflicted with the trial on Wednesday. You will not find leprosy except (by having Hijamah) on Wednesday or Wednesday night.” [Sahih-Sunan-ibn-Maajah (3487)