I applied months ago and have not received a card. How do I go to a health provider and prove I have coverage?
If you enrolled in a plan and paid your premium, but don't have your insurance card yet, you can call your insurer and collect the information you need. You can see examples of what information is on a health insurance card here.
For your doctor to file a claim properly they could need your health plan carrier name, member ID, and group number. There is other helpful information on your card, but these are the key parts.
The above being said your best bet is to hound the insurer a bit until they get the card to you. You shouldn't wait to get treatment until you have the physical card (if you have confirmed with your insurer that your coverage is active). However, you can run into issues with insurers not paying claims if they aren't field in the wrong way or if you go for a treatment that isn't covered. So again, the best protection is simply getting on the phone with the insurer before taking action unless it's an emergency.