Praise be to Allah.
Fasting Ramadan is obligatory for every adult, sane, non-travelling, healthy Muslim, because Allah says (interpretation of the meaning):
“O you who believe! Observing As-Sawm (the fasting) is prescribed for you as it was prescribed for those before you, that you may become Al-Muttaqoon (the pious).
184. [Observing Sawm (fasts)] for a fixed number of days, but if any of you is ill or on a journey, the same number (should be made up) from other days”
[al-Baqarah 2:183, 184].
Fasting is one of the five pillars of Islam on which it is built, as is well known and established, and all Muslims show great respect for this duty of fasting throughout the Muslim world. Allah says (interpretation of the meaning):
“Thus it is [an obligation that mankind owes to Allaah] and whosoever honours the Symbols of Allaah, then it is truly, from the piety of the hearts”
See also the answer to question number 38747.
What the Muslim should do is honour this symbol because Allah has honoured it, and he should beware of taking the matter lightly. He should strive to find all possible means of preserving it as Allah has enjoined. If it is too difficult for him to fast whilst working, then he has to shift his work from daytime to night-time, if that is possible. These kinds of regular operations -- i.e., those that are not emergency cases -- can be done at night as easily as by day, as is the practice of many doctors.
If it is not possible for him to shift his work to the night-time, then he must take his annual leave during the month of Ramadan or during part of it at least, if it is possible for him to do that, and devote that time to fasting.
If that is not possible, and he cannot find other work in which he can fast during the day in Ramadan, and he will be harmed by giving up his job, then it is permissible for him to break the fast on the days on which fasting causes considerable hardship, but he should not break the fast just for fear of hardship; then he should make up the days that he did not fast during his weekly break or on other days when he is able to make it up, on condition that he complete making up the days that he did not fast before Ramadan begins in the following year.
It says in Sharh Muntaha al-Iraadaat (1/478): If a person's work is hard and he will be harmed by giving it up and he is afraid of physical harm, then he may break the fast and make it up later on. This was stated by al-Aajurri. End quote.
In al-Mawsoo‘ah al-Fiqhiyyah (28/57) it says: The Hanafis said: With regard to those whose work involves physical effort and who are in need of their earnings, such as bakers and harvesters, if he knows that if he works he will encounter harm that may make it permissible for him not to fast, then it that case it is haraam for him to break the fast before he actually encounters hardship. End quote.
It says in Fataawa al-Lajnah al-Daa’imah (10/244): It is not permissible for a worker to break the fast during the day in Ramadan just because he is working, but if he encounters great hardship that forces him to break the fast during the day, then he may break the fast with something that will ward off that hardship, then refrain from eating and drinking until Maghrib, when he may break the fast with the people but he should make up that day on which he broke the fast. End quote.
And Allah knows best.