In deciding what to do you need to think about at least three things. These are the type of chemotherapy you are going to have, the side-effects you might personally experience and what your normal work is.
Most types of chemotherapy are given for one, or a few, days followed by a rest interval of two to four weeks, with on further treatment, and then the cycle is repeated. This usually goes on for about six cycles, lasting four to six months in all. Many different drugs are used in different types of chemotherapy and this means that the side-effects of the various treatments vary very greatly. For some types of chemotherapy side-effects are few and mild whilst for others they are much more troublesome.
Furthermore each of us is unique and responds to situations in different ways. This is just as true for chemotherapy as it is for other things in life. This means that people having exactly the same drugs at exactly the same doses will often vary considerably in the number of side-effects they develop and the degree of upset they have from those side-effects. So even with chemotherapy treatments which are in widespread use, where all the likely problems are well known, it is still impossible for doctors and nurse to predict in advance exactly what side-effects any individual patient will get and how well they will cope.
Finally you need to think about your job. First of all, is it very strenuous, with a lot of physical effort or stress. If it is then you are less likely to cope than if your work is quite light and undemanding. Secondly, how flexible are your employers, will it be easy for you to adjust the hours and days you work at short notice or do you have to give definite commitments on working times, one way or the other, well in advance?
Have a chat with your doctors and nurses, if they feel that your particular chemotherapy is going to be quite intensive with a high risk of troublesome side-effects then it is probably best to plan to take time off for the duration of your treatment.
If your medical team feel that your treatment is less likely to be troublesome, and your employers are flexible, then you could adopt a 'try it and see' approach. Book time off to cover the first couple of weeks and then, if you find you have very few problems with your first treatment you could arrange to have just a few days off at the time of each chemotherapy drip and carry on working in between. But bear in mind that sometimes, even with gentle chemotherapy, as the courses go on you may become progressively more tired and lose some of your stamina and feel less like work. If your bosses are less flexible and need to know definitely, well in advance, just when you will be working then probably the safest thing is to take the time off whilst you are having treatment - if, as time, goes on, you find you really are coping well then you could always discuss with your doctors and your employers the possibility of starting back sooner.