"The fast is performed to learn discipline, self-restraint and generosity, while obeying God's commandments. Fasting (along with the declaration of faith, daily prayers, charity, and pilgrimage to Mecca) is one of the 'five pillars' of Islam." 2 However, Muslims who fall within one of the following categories may elect to not observe the fast:
Children under the age of puberty.

People who are mentally incapacitated or not responsible for their actions.

The elderly.
The sick.
Travelers who are on journeys of more than about fifty miles.
Pregnant women and nursing mothers.
Women who are menstruating.

Young children are encouraged to fast as much as they are able. 2

A full daytime fast can be very stressful for many people. Professor Saghir Akhtar has written an online essay for the BBC with health and diet advice during Ramadan. 3

Dr. Asim Padela, a Muslim and an emergency room physician at the University of Chicago Hospital, suggests that Muslims with health concerns should consult with their doctors and religious leaders to decide if they can safely fast. He said that because of the temperature and length of daylight:

"It is going to be difficult this year [2013] for many people, at least in this part of the world. ... Thereís a very granular level discussion that needs to occur at the level of what the patientís circumstances are, what their illness is, what their comorbidities (existing conditions) are and what their body, their physiology can tolerate and not tolerate."

Dr. Michael Finkelstein. an associate medical officer at Toronto Public Health, says that people who are fasting need to make sure they drink enough fluids during the hours when the sun is down, and need to keep dehydration in mind. He said:

"June is a pretty hot month here. So they need to be aware of the early signs and symptoms of dehydration. Things like dizziness, light-headedness, headaches, intense tiredness, dry mouths and obviously the colour of their urine can get quite dark ó those are indications that their fluid balance is in trouble. So if there are things that need to be done that donít have to be done during the middle of the day, try to move those to times during the day when itís cooler ó early evening or early in the day so that you can avoid stressing your body at the height of the heat of the day." 7

Those who are temporarily unable to fast are expected to make up the missed days at another time. Alternately, they can pay "fidah" (compensation) which involves a monetary donation of about $10.00 per day to feed the poor.

Muslims may engage in a number of religious activities during Ramadan:

Some read the entire Qur'an.

Taraweeh prayers (a.k.a. the night prayers) are said every evening during Ramadan in addition to the normal five prayers recited each day of the year.
Some of the Muslims spend their entire night praying to Allah. 4

Muhammad observed Al-I'etikaaf (retreat) during the last ten days of Ramadan. Some contemporary Muslims do the same by staying in the mosque over a number of days. They store provisions in a corner of the mosque, and engage in spiritual pursuits, such as prayer, recitation of the Qur'an, glorification of Allah, studying the Hadith, etc. 5

"During the entire month of Ramadan the Lailatul Qadr is the most special night for all the Muslims who fast. It is believed that Lailatul Qadr night falls during the last 10 days of Ramadan during the odd days like 21st, 23rd, 25th, 27th or 29th. But many Muslims believe this "night of power" to be on 27th as it was originally on that day." 4 This night is believed to be when Muhammad first received the Qur'an.