Does taking a blood sample of 5 cc affect the fast?

A small blood draw for analysis does not affect or invalidate the fast, as it is minor and does not weaken the fasting person, nor is it among the known invalidators of the fast according to Islamic law. As for drawing a large amount of blood for donation, if it affects the body like cupping (hijama), then it invalidates the fast. It is not permissible to donate this large amount of blood if the fast is obligatory, except in cases of extreme necessity that cannot be postponed. In such cases, the donor breaks their fast and must make up that day.