Are car windows already tinted?

I have a 2005 Honda and my windows look very slightly tinted. Like how most car windows look. I need to get a tint for medical reasons, but I plan to get 70%. My state allows 70% but I'm worried because I may already have 5% tint.

Also is tinting the windshield 70% a bad idea?

It sucks when is raining. You can't see anything in side mirrors.

Only a light meter knows for sure. If you have a medical need for tint and a doctors note to prove it, you shouldn't have a problem. Get a professional to do it, as the doctor ordered, and keep the paper work handy. If the police stop you, that paper work should make them let you go. You know why there are tint laws? It's not to stop people with medical conditions from following their doctors orders.