Is it permissible for him not to fast because he has chronic constipation and needs to take medication and laxatives?
Question

I have been suffering from chronic constipation for more than ten months. This constipation is accompanied by stomach pain and discomfort for most of the day, and I need to use laxatives and medications to relieve it. Please note that this sickness – may Allah spare us and you from it – usually lasts for months and years, and may remain with some people for the rest of their lives. Is it obligatory for me to fast, or do I come under the ruling of one who is sick, so I should fast when I am able to and pay expiation for the days on which I do not fast, after Ramadan ends?
Praise be to Allah.Firstly:
Guidelines on the type of sickness that makes it permissible not to fast
If the sickness is accompanied by pain and real hardship, and not fasting will ward that off from the one who is afflicted with it, then this is an excuse that makes it permissible not to fast.
Allah, may He be exalted, says (interpretation of the meaning):
{O you who have believed, decreed upon you is fasting as it was decreed upon those before you that you may become righteous –
[Fasting for] a limited number of days. So whoever among you is ill or on a journey [during them] - then an equal number of other days [are to be made up]} [al-Baqarah 2:183-184].
The sickness that makes it permissible not to fast is the sickness which causes the fasting person real hardship.
an-Nawawi said in al-Majmoo‘ (6/261): The sick person who is unable to fast because of a sickness from which there is hope of recovery is not obliged to fast.… This applies if he will suffer real hardship when fasting. It is not stipulated that he should have reached the state in which he is unable to fast at all. Rather our companions said: For it to be permissible not to fast, it is stipulated that fasting should cause significant hardship that makes it difficult to fast. End quote.
And he said:
With regard to mild sickness that does not cause real hardship, it is not permissible for him not to fast, and there is no difference of opinion among us concerning that". (Al-Majmoo‘  6/261).
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:
Sickness is of varying degrees:
The first is that which will not be affected by fasting, such as a mild cold, a slight headache, a toothache and the like. In this case it is not permissible for him not to fast, even though some of the scholars say that it is permissible for him not to fast, because of the general meaning of the verse (interpretation of the meaning):
{… and whoever is ill  …} [al-Baqarah 2:185].
But we say: If this ruling is based on a reason, which is that not fasting is kinder and more helpful to him in coping with the sickness, then in that case we say that he may not fast. But if the sickness will not be affected [by fasting], then it is not permissible for him not to fast and he must fast.
The second degree is if it is difficult for him to fast, but it will not harm him. In this case, it is disliked (makrooh) for him to fast, and it is Sunnah for him not to fast.
The third degree is if it is difficult for him to fast and it will harm him, such as a man who is affected by kidney disease or diabetes, and the like. In his case, fasting is haraam". (Ash-Sharh al-Mumti‘  6/341).
Based on that, if you will suffer real hardship from fasting, for which you need to take medication or laxatives by mouth, it is permissible for you not to fast.
But if the medication can be taken by injection or by rectal suppositories, this does not invalidate the fast, so in this case it is not permissible to take the medication by mouth, because that breaks the fast in Ramadan with no excuse.
It says in a statement of the Islamic Fiqh Council regarding things that break the fast:
The following things are not regarded as breaking the fast: ...
8.. Therapeutic dermal, intramuscular or intravenous injections, excluding fluids and nutritional injections…
11. That which enters the body by absorption through the skin, such as creams, ointments, and medicated skin patches containing pharmaceutical or chemical substances. End quote.
Secondly:
Sick person making up fasts that he missed in Ramadan
If you do not fast, then the matter should be examined further: if the sickness is one from which there is hope of recovery, even after a few months, then in that case you may not fast, and you should make up the fasts later on, when it becomes easy for you to make them up, even if you spread out the days on which you fast, and it is not acceptable for you to feed poor people instead.
But if a trustworthy doctor says that it is a sickness from which there is no hope of recovery, and you cannot fast except with real difficulty, because you need to break the fast in order to take medicine, then in this case you should feed one poor person for each day.
And Allah knows best.