A person who is not able to fast have to either make up for the missed days, or pay fidyah, a religious donation made in Islam when a person cannot fast. This donation can be in the form of food or money to be used to feed the ones in need.
A person that is not terminally ill, a travelling person, and a woman that is menstruating or in the state of post-natal bleeding should only make up for their missed days.
A person who is ill terminally and an old man or old woman can only pay fidyah, which is according to Abu Hanifah, a saa’ of whole wheat for every day missed. They don’t have to make up for their missed days of fasting.
According to Abu Hanifah, a woman that is pregnant or breast feeding only have to make up for their missed fasts later after Ramadan. The pregnant woman only makes up for her missed fasts and the woman that is breastfeeding makes up for missed day, as well as pays fidya, which is one mudd for every missed day.
A single saa’ contains 4 mudd, and one mudd is 2 normal handfuls. A saa’ in volume is calculated at approximately 2.75 liters. As for the weight of the saa’, it varies from type to type.
What is most recommended to pay is not cash but in actual food, because Allah (SwT) says what means; “And for those who can fast with difficulty (like old people), they have a choice, either to fast, or feed a poor person.”
According to Ibn Abbas (may Allah ‘SwT’ be pleased with him) this refers to old men and old women who cannot fast, so they should feed one poor person for each day.
If a doctor stated that you cannot fast from the sickness, and there is no hope for you to recover, then you must feed one poor person for each day missed. You should give half a saa’ for the local staple food, whether it is rice or something else. It will be sufficient if you give a poor person dinner or breakfast for the number of days you did not fast.
So therefore, the elderly or sick person who has no hope of recovering from their sickness should feed one poor person as you will feed yourself for each day that you missed.