The lunar calendar has 12 months. Ramadan is the 9th month of the Islamic Calendar.
Every accountable Muslim is obligated to fast the month of Ramadan. Although, note that a woman in her menses or post-partum bleeding is not obligated to fast. Moreover, if she did fast, her fast would be invalid. Instead, she needs to make up the missed days some time after the day of ^Eed Al-Fitr.
Integrals of fasting:
It is obligatory :
1. Each night (between Maghrib and Fajr) to make the intention (in one's heart) to fast the following day;
2. During the fast one needs to abstain from sexual intercourse, masturbation, inducing vomit and inserting anything with a volume into the head or the body cavity through an open inlet, excluding one’s pure, tahir saliva while inside the mouth.
One’s fasting is valid as long as one does not become insane, even if it were for a moment, and also if one does not lose consciousness the whole day, i.e., from dawn until sunset. However, sleeping throughout the entire day does not render the fasting invalid.
Note that the use of athma inhalers invalidates the fast. However, if one is in need to use them one is permitted to do so without being sinful.
As to the use of injections, whether intravenous, intramuscular or subcutaneous, this does not invalidate one’s fast.
Invalidating the fast of one day of Ramadan by engaging in sexual intercourse without an excuse is sinful. One must make it up immediately, and one must fulfil an expiation of dhihar. The expiation of dhihar is to free a Muslim slave; if one is unable he fasts two consecutive lunar months; and if one is unable he feeds sixty poor Muslims. To feed sixty poor Muslims means to give every one of them a mudd of wheat or another grain--whichever is the most common staple food in that town. The mudd is the fill of two cupped, average-sized hands.
Those who are excused from fasting:
Even if fasting is not tedious, it is permissible for the traveller of a shortening distance (qasr) not to fast. Breaking the fast is permissible for the sick person, the pregnant woman, and the nursing woman who cannot bear the hardship of fasting. However, making up the missed days is obligatory.
