Have you ever called off work before?
The NHS relies on employees to be at work so that patients can be seen as scheduled. The interviewer wants to know that you are a reliable person and they will not have to constantly find coverage for your shifts. Discuss your commitment to the company and speak to times you've had to call out of work in the past. If you don't have work experience, think about times you've missed class, internships, or other volunteer responsibilities. No matter the situation, demonstrate that you handle these types of situations with professionalism.
"I have called off from work twice in the last year, but only when I was very ill and with a doctor's note. If I am not feeling well, I notify my manager with as much advanced notice as possible so that my shift can be covered. I enjoy my job and need to earn a living, so rest assured that I will be at work on time and when expected."
