I can speak English. I might still want Mandarin for this.
Some things are easy to say in English. Describing exactly what feels wrong, or what frightens me, might feel easier in Mandarin. I would want the language that lets me finish the thought.
When booking, I would ask about language support or an interpreter. I would write my two or three main questions in the language that comes most naturally, with medicine and test names alongside them.
Before leaving, I would say the plan back in my own words: “So this is what I do next, and this is when I come back?” I would ask for another explanation where needed and write the arrangements down.
I would want a conversation about my health, not an English exam. Being understood would help me feel more settled.