How do you answer a question about your weaknesses in an interview without jeopardising your chances of success?

First and foremost, don't let this (not uncommon) question catch you out! Questions like these are more often designed to see your ability to self-reflect than they are to catch you out. The question doesn't require you to reel off a huge number of different 'weaknesses', but rather to think about one personality trait and expand upon how you feel this may impact you in your medical studies. The best way I found to approach this type of question is to give an example of a weakness, discuss how this may be perceived to be an issue in medicine (this can also be used to demonstrate an understanding of what medicine entails), and how you plan to approach with this 'weakness'. Nobody's perfect, so having an example that you have thought about a little before will mean you don't get taken aback when this question is asked of you.