For everyone's convenience let me quote the relevant paragraphs
[The Qur'an instructs Muslims to fast during the month of Ramadan, but also gives clear exemptions for those who may become ill as a result of fasting:
"But if any of you is ill, or on a journey, the prescribed number (of Ramadan days) should be made up from days later. For those who cannot do this except with hardship is a ransom: the feeding of one that is indigent.... Allah intends every ease for you; He does not want to put you to difficulties...." - Qur'an 2:184-185
In several other passages, the Qur'an instructs Muslims not to kill or harm themselves, or cause harm to others.]
Here is a link that is relevant to your question
http://islam.about.com/od/ramadan/a/ramadan_health.htm
For everyone's convenience let me quote the relevant paragraphs
[The Qur'an instructs Muslims to fast during the month of Ramadan, but also gives clear exemptions for those who may become ill as a result of fasting: