It is legislated for the sick Person to break his Fast

Question :

I am 16 years old and I am being treated in a hospital for the past 5 years. During the month of Ramadhan last year the doctor ordered that I be given some chemical medicine in the vein of my neck while I was fasting. The medicine was strong and it affected my stomach and all of my body during the same day that I took it, causing me to be severely hungry. After less than seven hours had passed since Fajr, at approximately 'Asr time, I began to feel pain from the hunger and felt as though I was about to die, but I did not break my fast until the Athan of Maghrib. During the month of Ramadhan this year, if Allâh wills, the doctor will again order that I be given that medicine. Should I break my fast on that day or not? If I do not break my fast, do I still have to make up for that day? Does taking blood from the vein of the neck break the fast or not? Likewise, concerning the medicine that I mentioned (does it break the fast)?

Answer:

It is legislated for the sick person to break the fast during the month of Ramadhan if the fast is harmful to him or difficult upon him or he needs to take some medicine during the day. This medicine could be various types of pills, syrups and so forth, from that which is eaten or drunk. This it due to Allâh's Statement:
"And whoever is ill or on a journey, then (he may make up for his fast from) a number of other days."

It is also due to the Prophet's statement:
"Verily, Allah loves that His concession be taken just as he hates that disobedience of Him be done."

In another narration he said:
"...just as He likes for His Decisions to be followed."

In reference to taking blood from the vein of the neck for blood tests and other purposes, the correct view is that it does not break the fast of the fasting person. However, if it is a lot, then it is better to delay it until night. If it is done during the day, it is safer to make up for the day of fasting, as it resembles cupping.

Source:
Ash-Shaykh Ibn Baz
Fatawa Islamiyah, Vol. 3 Pages 284-285