You would normally be register again for the full course. However, departments, upon being advised of the situation, have other discretionary options that may be applied. (Refer to the current issue of the Faculty Handbook, Exams Only Regulations 11.2.)
If you missed an examination for medical reasons, you should submit a signed medical certificate within seven days to the Examination Section of the Registry. (Refer to Examination Regulations, Section II, 17-32)