There was a person who had a chronic disease and the doctors advised him not to fast at all, but then he consulted doctors in another country and was healed by Allah's leave, five years later, when five Ramadans had gone by in which he did not fast. What should he do after Allah healed him? Should he make them up or not?.
If the doctors who advised him not to fast at all were Muslim doctors who were trustworthy and had knowledge of this kind of disease, and they told him that there was no hope of recovery, then he does not have to make it up, and his feeding the poor is sufficient, but he has to fast in the future. End quote.
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him)