Keep an accurate work diary, something high enough detail that you can look back on in several months and know what you were doing at what time on what day. Something you can then use to answer the question “Exactly, how many time this month were you asked to do X”, and the answer be precise.
Sounds like you might be being asked to do things you haven’t had training for, and don’t have the certificates for. In which case this becomes a legal liability issue, and something they can’t ignore, and can’t fire you for.
Also, be careful of the difference between “I have been asked by a manager to do this” and “noone else was doing it so I felt I had to”. If you’re speaking to patients about their medical issues without training or being specifically asked to, you could be getting yourself into trouble too.
The diary thing is useful for everyone in every job really. In your annual review (or quarterly, whatever) it’s incredibly useful to provide facts and figures for what you’ve been spending time doing. Particularly if you’ve got a manager who wants to downplay your efforts, or if you’re asking for pay rises/ bumps up to higher grades.
Tom Scott has a video on it