A Muslim should be aware of the things that invalidate his fasting in order to avoid them and thus safeguard his worship. Special concern has risen in modern age particularly regarding some medical tools or drugs used during fasting, which necessitates some kind of ijtihad.

Sheikh `AtiyyahSaqr, former head of Al-Azhar Fatwa Committee, states: As regards fasting, Allah, Exalted be He, says, (So hold intercourse with them and seek that which Allah hath ordained for you, and eat and drink until the white thread becometh distinct to you from the black thread of the dawn. Then strictly observe the fast till nightfall.) (Al-Baqarah 2:187) Also, it’s reported that one of the Prophet’s Companions told him: “I am ruined.” The Prophet (peace and blessings be upon him) asked him: “Why?” The man replied: “I had sexual intercourse with my wife in the day of Ramadan.” The Prophet (peace and blessings be upon him) then explained to him how to expiate it.

Both the above-mentioned verse and hadith indicate that fasting means abstaining from food, drink and sexual intercourse. Thus, eating, drinking or having sexual intercourse invalidates one’s fasting. Jurists have unanimously agreed that he who commits any of those three acts must make up for the fast-day he missed, since that would be a debt, and “a debt owed to Allah merits even greater consideration” as was stated in an authentic hadith. Additionally, having sexual intercourse requires grand expiation, namely freeing a slave. If a Muslim is unable to do so, he is to fast two consecutive months. If he is still unable to, he is to feed sixty poor people.
Jurists differ on the exact definition of food and drink. Some scholars maintain that eating and drinking involve anything reaching the interior of one’s body. Yet, they differ as to whether “anything” is to be understood in a general sense or is intended to mean something in particular, including food and fulfilling one’s lusts. They also differ on the meaning of “interior”: does it mean one’s stomach which receives food and drink or the parts of the human body that cannot be seen when looking at him or that organ which digests food and medicine? Consequently, some hold that placing one’s finger inside one’s ear invalidates fasting. Conversely, some of them are also of the view that when food manages to find its way to the body, not through an open tract, such as with the aid of needles, one’s fasting is not invalidated. Others point: Should any substance reach the throat from beneath the hair, through the pores, one’s fasting is invalidated, despite the fact that this is an unconventional channel? On the other hand, some of them state: Inserting a syringe into the urethra does not break one’s fast, although the latter is an open tract. Not taking into consideration the true significance of fasting and relying on a generalized concept of food that included things distant from the literal and customary meaning of the term, those jurists issued such varied rulings.
However, of all the famous jurists’ views, I select only the following:
1. Fasting is not invalidated on account of placing one’s finger inside one’s ear, or because of cleaning it with a cotton pad or a solution, since nothing can permeate the ear drum and reach the head, which, in turn, is not an organ that receives food which nourishes the body.
2. Fasting is not broken by vaginal examination, examination of piles or tonsils using a spoon or things of the sort.
3. An enema does not invalidate fasting unless the tool reaches the stomach.
4. Fasting is not invalidated by intravenous, intra-muscular or subcutaneous injections, since they do not provide one with food or drink that satisfies hunger or quenches thirst.
5. Nutritive injections, such as glucose injections and the like, are conventionally regarded as food that does break one’s fast. Whoever takes nutritive injections can do without food for a long time as they satisfy hunger the way food does. This is in effect because when food is digested and absorbed, it is circulated in the blood to the entire body to meet its needs. Alternatively, nutrition could be directly injected into the blood without necessarily passing through the alimentary canal.
6. Cooling off the body with cold water or the mouth by gargling does not invalidate fasting since the Prophet (peace and blessings be upon him) was seen pouring water on his head in the blistering heat while he was fasting. This was narrated by Ahmad, Abu Dawud and An-Nasa’i. This is because cooling off the body does not involve the water reaching the stomach. It merely aims at stopping perspiration in order to retain the water in the body so as to reduce thirst.
7. Vomiting: It is reported that the Prophet (peace and blessings be upon him) said: “Whoever is overcome and vomits is not to make up for the fast day, and whoever vomits intentionally must make up for the fast day.” Jurists maintain that vomiting is the coming out of substances from the stomach through the mouth. If vomiting takes place accidentally, it does not break fasting. If it is deliberate, one’s fasting is broken.