Some courses will give you access with no experience but many will require you have experience in the area of interest.

In countries such as the UK more newly graduated undergraduates are taking up post-grad courses because they can't get jobs. So you can do it but is it the best way?

In my opinion if you haven't had some experience to draw on then you won't be going into the course with personal patient knowledge that you can reflect on. One of the most instructive processes of post graduate education is thinking about cases where you didn't succeed, or would like to have done better or you got a surprise result, or how you could further develop your knowledge and skills to treat a patient group you are familiar with.

If you are doing a research degree then that is a bit different. However your lack of clinical experience may mean your research question and approach is "off the mark" or lacks meaning, is "too theoretical"

I got so much more out of my post grad experiences when I knew more of what I was doing or not doing well in clinical practice.