He has tuberculosis and the doctors have advised him not to fast for five years
Question

                I am a tuberculosis patient. I was under treatment for two years and the doctors advised me not to fast, and scared me that if I fast the disease will come back to me. They advised me not to fast for five years. What is the ruling on doing this?.
Praise be to Allah.
    Allaah says (interpretation of the meaning): 

    “So whoever of you sights (the crescent on the first night 
    of) the month (of Ramadan i.e. is present at his home), he must observe Sawm 
    (fasts) that month, and whoever is ill or on a journey, the same number [of 
    days which one did not observe Sawm (fasts) must be made up] from other 
    days”

    [al-Baqarah 2:185]. 

    i.e., if a person is physically sick and it is too hard for 
    him to fast or he will be harmed by fasting, or he is travelling, he is 
    allowed not to fast, but he has to make up the number of days that he did 
    not fast. Hence Allaah says (interpretation of the meaning): “Allaah 
    intends for you ease, and He does not want to make things difficult for you” 
    [al-Baqarah 2:185]. The scholars have stated that if a trustworthy 
    Muslim doctor states that fasting will be harmful to a sick person, or will 
    make his sickness worse or delay his recovery and the like, then not fasting 
    in this case is permissible according to sharee’ah. If the doctor is not 
    Muslim, or he is Muslim but he is not of good character, then his opinion 
    should not be accepted except in cases of necessity, such as if it is not 
    possible to ask another doctor. If it is a necessity and other factors 
    indicate that the non-Muslim is telling the truth, such as if the sick 
    person feels the same thing, or it is well known that this sickness is 
    something that gets worse with fasting and that will make recovery 
    difficult, then in that case it is permissible not to fast until Allaah 
    heals him and he becomes strong enough to fast without adverse effects. 

    With regard to the past months, you have to make them up after you recover, and there is no expiation for delaying it, because you did not make them up because you were still sick. End quote.