Fasting in Ramadan is based on a rationale. One, it is prescribed for a fixed number of days. Two, specially circumstanced are exempted. Specially circumstanced could be the persons suffering illness, or the ones on a journey. It may also include persons bound to face hardship, were they to fast, such as the ones in advanced age. The exemption granted in such instances is nevertheless conditional, as enshrined:
‘’(Fasting) is for a fixed number of days; but anyone of you is ill or on a journey, the prescribed number of days (should be made up) from days later. For those who can do it (with hardship), is a ransom, feeding of one that is indigent. But he that will give more, of his own free will—it is better for him. And it is better for you that ye fast, if ye only know.’’ (2:184)
The person suffering an illness during the period of Ramadan may make up the number of days; he did not fast, later. Same holds true for the ones on journey. The exemption granted for journey is commented upon in a varied manner by different commentators. While some say three marches, others make it more precise by making it a journey of 16 farsakhs (48 miles). However this is again open to varied interpretations, subjected to whether a journey is undertaken on foot, on an animal ride, such a camel, or on modern means of transportation, such as an automobile or aircraft. Hence it is related to, what the case might be, and how could it be determined. In such circumstances, a person has to be their own judge.
Persons with advanced age, for whom it is hard to undertake a fast, may feed one indigent person instead. But as the Holy Verse lies down, he may do more, of his free will. Exemption is granted also for a lady, who is carrying or lactating a baby, however some schools of thought suggest that it may be made up later.
Having made a provision for persons with advanced age and specially circumstanced, the principle holds, as noted in the conclusion—‘’And it is better for you that ye fast, if ye only know.’’