Whoever is ill in the month of Ramadan, and fears that, if he fasts will adversely affect him should not fast and he performs it as qaḍā’. No Expiation is due from him.
A sick person who fears that the illness will worsen. This also includes a sick person who fears prolongation of his illness or intensify or delay recovery, or even a healthy person who fears becoming ill due to the fast. In either case, the fear of course must be a genuine fear, not just mere delusion. This includes the elderly. Being simply old does not mean one does not fast.
A pregnant woman or nursing woman, with the condition for each that she have a legitimate fear for the baby or for herself.
Legitimate fear may be either (1) past experience, even if of someone else with the same sickness; (2) an obvious sign of potential harm; or (3) an opinion of a qualified Muslim physician who does not sin in public. The same would apply for a healthy person that has a legitimate fear, based on one of the above indications, of becoming ill. If one were to break the fast without one of the above indications, then he would have to perform expiation.
In these cases qadha is made without kafaarah.
If one is a traveller, who is not harmed by fasting, then that he fast is better, but it is permitted for him not to fast but to delay the performance of the fast. If he decides to fast, then he cannot break it. If he is a resident before Fajr, then he must fast and break it when he travels. It is preferred he begins his journey before Fajr. It is better for the traveller to follow the group in fasting.
If a traveller arrives to his place of residence, and was not fasting on his journey he should abstain from eating.
If the ill person or the traveller dies, and they were both in that state of illness or journey, qaḍā’ is not binding upon them. If, however, the ill person recovers from his illness, or the traveller becomes a resident and, thereafter, they die, qaḍa’ is binding upon them to the extent of the duration of their becoming well or adopting residence respectively.
A woman menstruating or undergoing postnatal bleeding is exempt. If a woman in menstruation or postnatal bleeding becomes pure during the day, she should abstain from eating for the rest of the day.
One who is undergoing severe thirst from which he fears death, likewise with food is exempt.
The decrepit old person who is not able to fast should not fast. He should instead (fidya) feed one needy person for each day [of missed fasting or its equivalent monetary value] for each day. The same can be said for those who have chronic illnesses that prevent them from fasting.
Whoever dies and the qaḍā’ of Ramadan was due from him, and he had put it in his will, his executor (walī) should feed on his behalf one destitute person for each day [missed] a half ṣā‘ of wheat or a ṣā‘ of dates or barley. This is a pertinent point to bear in mind for deceased relatives who were known not to fast, some of the inheritance should go towards alleviating them of their qada fasts.
Fidya
The Fidya is to feed one person two meals for each day one misses a fast.1
If one is unable to2 then they are to seek forgiveness.
Some fatawa state to give the poor person monetary value daily, otherwise if given all at once, they may no longer be classed as someone poor.