All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
There are two ways a woman can have a breast lift:
Firstly, a non-surgical lift using drugs and medication. There is no harm in this on condition that these medications are not hazardous to her health.
Secondly, a surgical breast lift and there are two scenarios:
1) If the purpose of the surgical treatment is to correct a mild sagging of the breasts and for cosmetic purposes to resize their shape in accordance with a woman's preference, then she should not undergo such a surgery because it would constitute changing the creation of Allah, the Exalted. Allah, the Exalted, says about Satan (what means): {(Satan said:)"...and I will command them so they will change the creation of Allah." And whoever takes Satan as an ally instead of Allah has certainly sustained a clear loss.} [Quran 4:119] Moreover, Ibn Mas‘ood said, “The Prophet, sallallaahu ‘alayhi wa sallam, cursed those (women) who change the creation of Allah.” [Al-Bukhari and Muslim] Indeed, the prohibition is more emphasized and the sin is even greater if the surgery is performed by a male doctor because this implies exposing her ‘awrah (what should be covered of the body) and it being gazed upon.
2) If the sagging is excessive to the point where it is very noticeable, is hazardous to a woman's health, and causes unbearable harm or that keeping them that way constitutes extra hardship for her, then there is no problem in having a breast lift surgery. It should be performed by a female doctor, if available, otherwise a male doctor can perform the surgery, but he should not be alone with the patient.
Allah knows best.