If you're just going to a regular doctor and have no way to pay the doctor or have no health insurance to pay the doctor then yes that doctor can refuse to see you or treat you.
A doctor can refuse to treat patients for non payment but an emergency room cannot.
So if you do need medical help and cannot pay right now or do not have any health insurance you should go to the emergency room and at an emergency room they must treat the patients.
That is especially true if the treatment is a medical necessity as no emergency room can legally refuse to treat a patient when they come in.
Even if you have no money or no health insurance the emergency room has to treat you.