In the Writing Sub-test, you are often expected to take facts from the Case Notes and express them in your own words, when you write the referral letter.
In the Reading Sub-test, you may have to do the same in the completion activity as well as the Multiple Choice activity.
It's a good idea to develop lists of vocabulary around a topic, so that you can gather as many similar terms as possible (remember that English has a large number of synonyms - different words with the same meaning).
Take a look under the Writing hints tab of this website and try the latest Quizlet activity. The topic is 'Describing the Patient's Condition'. You will find a list of words which describe changes in the condition of a patient.
Most of the words can be used in the general English as well as medical English senses.