Hijama (wet cupping) can be performed at any time, however it is traditionally considered to be more effective at certain times of the month. These are known as the Sunnah days.
These more effective times of the month are dependant on the phase of the moon and the pull it is exerting on our planet. This pull has an effect on many things ranging from the ocean tides to the pressure and flow of blood inside your body.
The best time for Hijama (wet cupping) is around the middle of the lunar month, two or three days after the full moon. This is a time when the gravitational pull from the moon is the strongest.
According to Ibn Sina, the four humors inside the human body are on the rise and in a state of agitation during the full moon. The full moon pulls the blood to the calmest parts of the body where it settles in the shoulder blade area when the moon begins to decrease from the 17th -27th day of the lunar cycle.