1) One who is ill and the traveller. It is upon them to make up (for any) days (of fasting in Ramadhaan they missed).
Allaah (Subhaanahu wa Ta'aala) says:[Observing Sawm (fasts)] for a fixed number of days, but if any of you is ill or on a journey, the same number (should be made up) from other days. And as for those who can fast with difficulty, (e.g. an old man), they have (a choice either to fast or) to feed a Miskeen (needy person) (for every day). But whoever does good of his own accord, it is better for him. And that you fast is better for you if only you know.][Soorah al-Baqarah, Aayah 184]
As for the ill person who is suffering from an illness from which a cure is not anticipated, then he is required to feed a poor and needy person for every day he misses (of fasting in Ramadhaan).
2) A woman on her menses or post-parum bleeding, then it is upon her to make up (for any) days she misses (of fasting in Ramadhaan).Aa.ishah (radhi-yAllaahu 'anhaa) said:We (the women on their menses or post-partum bleeding) were commanded to make up (for any days of) fasting (in Ramadhaan we missed), and were not commanded to make up for (any) prayers (missed) [The authenticity of this narration has been agreed upon by al-Bukhaaree and Muslim]
3) The aged from both the male and female who are unable to fast (due to the hardship of old age); they are required to feed a poor and needy person for every day (of fasting in Ramadhaan they miss).
4) The pregnant woman and the one breast feeding – if they fear for their health; they are required to make up (for any days of) fasting (in Ramadhaan they miss). However, if they fear for their child only, then they are required to make up (for any days of) fasting (in Ramadhaan they miss) in addition to feeding a poor and needy person for every day (of fasting in Ramadhaan) they miss.