If your sickness is one from which there is the hope of recovery, then after you recover you have to make up the fasts that you missed. But if your sickness is permanent and there is no hope of recovery, then you have to feed one poor person for each day that you did not fast.

It is permissible for civil defense workers to break their fast in extreme heat in order to rescue the injured, but it is preferable not to break the fast, except in cases of necessity, and they should make up that day.