[Does drawing blood with a medical needle nullify wuḍūʾ?]

Answer: Taking blood with a needle does not nullify wuḍūʾ. The scholars of the madhhab1 said likewise regarding the leech and mosquitoes and the like: if they suck more than a drop from the body of one in wuḍūʾ, it does not nullify wuḍūʾ.
Source : Min Thimār al-ʿIlm wa al-Ḥikmah vol.1