This is a pretty tricky situation. Imagine that you have been preparing for weeks to face a rather important exam. Ahead have passed dozens of hours of studies of which you have been able to get a lot of benefit. But, from one moment to another, your body can't take it anymore and you put sick. The worst thing is that it happens the day before. What to do in these types of situations?
It is a very big problem. First of all, keep in mind that everything depends on gravity. We can have from a simple headache to a constipation that does not even allow us to get out of bed. On the one hand, we can take some kind of pill in order to temporarily relieve pain (and give us time to do the exam) On the other, we may not be able to do that.
In the event that you can take a pill, everything will be arranged. It will work and you can go to the study center long enough to save the day. In the event that this is not the case, our main recommendation is that you call the institute and communicate that it will be impossible for you to go. It would also be convenient, the next day, to present some kind of receipt with the aim that the teachers give you the exam later. So you will not lose it.
In any case, when you see that you are going to have an important exam, you better get down to work to have your body in perfect condition. A) Yes there will be no drawbacks last minute.