IELTS Reading is basically a vocabulary test. If you don't understand words or phrases in the text, it will be difficult to get the right answers.
Try doing the test on page 46-49 of Cambridge IELTS book 4. Here is some of the key vocabulary from this test:
When I did this test with my students, nobody knew that a "chronic" illness means a "long-term" illness. The words "disillusioned" and "sceptical" also caused problems.
If you didn't know these words, look them up and write them down in your notebook. If you don't have a vocabulary notebook, you should start one now!