If you are sick, is it allowed not to fast? And if you decide to fast is it a sin? And what is supposed to be done by a person who is sick not able to fast?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

No doubt, diseases are of different types and kinds, some are serious and dangerous while some others are not as significant. So, some illnesses are addressed by the rulings of fasting while some are not regarded. Therefore, the ruling of an illness differs based on its seriousness. We can categorize a sickness that is regarded in fasting into three situations:

A) Sickness that does not affect fasting such as a light cold, slight headache, tooth pain, etc. In this case, fasting is compulsory and neglecting it is forbidden.

B) When a fasting person faces much hardship due to the sickness, but it does not cause any harm to him. In this case, the fasting is permissible, but it is dislikable to fast.

C) When the fast causes harm to the fasting person such as the diabetic or a kidney patient, etc. Fasting is forbidden for such a person.

However, Muslim scholars differ concerning the validity of the fast of a person whose situations is similar to the condition mentioned in the third category. Some scholars are of the opinion that if such a person fasts, he fulfills his obligation, while others believe that his fasting is not valid because he refused the concession granted by Allah. This is the opinion of Ibn Hazm .

Finally, the chronically ill person should break fasting, and fasting is forbidden for him if it could seriously harm him. We ask Allah to grant cure for Muslim patients.

As for the issue of making up the missed days, if the sickness of a person is temporary and he hopes for a cure, he should make up the missed days after being cured. Allah Says (what means): {… but if any of you is ill or on a journey, the same number (should be made up) from other days.} [Quran 2: 184]

The chronically ill person who has no hope for a cure is not subject to make up the missed days. Instead, he should pay expiation for every day he missed fasting. The expiation is feeding a poor person approximately 750 grams of rice or wheat or something else.

For more benefit on expiation for breaking fast, please refer to Fataawa 113006, 113207, 113713, 114215, 131133, 216094.

Allah knows best.