Sick note during internship?

Hello first of all.

I'm 18 and currently doing a two-week internship at a large production company. My health hasn't been the best for weeks, but for the past few days, it's been unbearable. I have stabbing headaches and abdominal pain, and I almost fall asleep when I stand, if I even have the strength to stand. I'm on my break right now and I regret coming here today because I feel absolutely terrible. I want to go to the doctor tomorrow to get checked out and ideally get a doctor's note for today, but I'm not sure how it will look to my "employer" if I'm absent during my internship.

Last week, I had to attend an important meeting and ended up arriving a little late for work (which was, of course, cleared up), so now I feel like I'm taking things to the extreme by calling in sick. I still have three days of my internship left, but I really need a day off; Otherwise, I won't get anything done and I might even collapse. All this heat isn't making things any better.

Would it be okay to take a day off or could the company refuse to give me an internship certificate at the end of the internship on the grounds that I wasn't there the whole time?

I don't mean that because I don't feel like working here, but really just because I can't stand being at work in this state and I realize that I'm making things worse.

Best regards ^^