There are a few rules and obligations for fasting in Ramadan.
1. Who must fast?
- Fasting in the month of Ramadan is obligatory upon every Muslim, male or female, who is adult (i.e. has reached puberty) and sane and who is not sick or on a journey.
- Sickness could be a temporary sickness from which a person expects to be cured soon. Such a person is allowed not to fast during the days of his/her sickness, but he/she must fast later after Ramadan to complete the missed days.
- Those who are sick with incurable illness and expect no better health, such people are also allowed not to fast but they must pay the fidyah, which is giving a day’s meals for each fast missed to a needy person.
- Women in their menses and post-natal bleeding are not allowed to fast, but they must make up later after Ramadan.
- Pregnant women and mothers who are nursing babies, if they find it difficult to fast they can also postpone their fasting to a later time when they are in a better condition.
- A journey is any journey that takes you away from your city of residence, a minimum of 48 miles or 80 kilometers. It is the same journey that allows you to shorten (qasr) your prayers.
2. How to fast (according to the Sunnah)
- Make the intention to fast for the sake of Allah every day before dawn. The intention need not be in words, but must be with the sincerity of the heart and mind.
- Eat a meal before dawn, known as suhoor. The best time for suhoor is half an hour before Fajr prayer.
- During fast abstain from all false talks and deeds.
- Do not quarrel, have disputes, indulge in arguments, use bad words, or do anything that is forbidden.
- Remain cheerful and pleasant during your fast.
- During fast one should do acts of charity and goodness to others and should increase his/her worship and reading of the Qur’an. Every Muslim should try to read the whole Qur’an at least once during the month of Ramadan.
- Break your fast immediately after sunset, when it is time for Maghrib prayer.
- Do not over indulge in eating after breaking your fast.
3. What breaks your fast?
Things that invalidate the fast and require qada‘ (making up for these days) are the following:
- Eating, drinking or smoking deliberately
- Taking any non-nourishing items by any body orifice (ie having a catheter inserted).
- Deliberately causing oneself to vomit.
- The beginning of menstrual or post-childbirth bleeding even in the last moment before sunset.
- Ejaculation out of sexual excitement from kissing, hugging, etc.
- Eating, drinking, smoking or having sexual intercourse after Fajr (dawn) on mistaken assumption that it is not Fajr time yet.
- Sexual intercourse during fasting is forbidden and is a great sin. Those who do so must make up the fast, and either fast 60 days after Ramadan or feed 60 poor people for each day the fast is broken this way.
4. What does not break your fast?
- Eating, drinking or smoking unintentionally, i.e. one forgot that one was fasting. But one must stop as soon as one remembers and should continue one’s fast.
- Taking a bath or shower.
- Using perfumes, wearing contact lenses or using eye drops.
- Taking injections or having blood test.
- Kissing between husband and wife is allowed in fast, but one should try to avoid it so that one may not do anything further that is forbidden during fast.
Taken from OnIslam.net