If something unexpected happens before or during your exams, for example you become very unwell or have an accident or experience serious family problems, don't ignore it. If you think the illness or distress will impact on your performance or if you think you will be unable to attend the exam, you must inform your institution.
There will be formal procedures at your institution about what you need to do. For example, you may have to fill out a 'mitigating circumstances' or 'exceptional circumstances' form. This may mean that if you take your exam and don't do well your institution may be able to take your circumstances into account. Each institution has its own procedures.
If you can't find the information that you need or don't know what to do, your personal tutor or your students union may be able to advise you.
If you don't attend an exam and don't inform anyone, you may obtain a zero mark, and you may not be able to take the exam again.