I'll give a wonderful example of doctors not treating all patients equal. My husband and I about 3 years ago were in an accident and were both taken to the ER, myself with a seperated shoulder, him with a broken wrist. Upon setting the bones and such (why wouldnt they give me anything for the pain before they decided to crank my shoulder I'll never know) and I was discharged first, with a script for 50 Motrin 500mgs (goodbyyyyyeeee liver!) the doc (same doc that treated me) was standing by my husband ASKING him what kind of pain med he wanted, a narcotic or not. I'm sure this doc could clearly hear from my yelps of pain that I was not a happy camper.. and my husband was laughing and joking with the staff.
When I asked this doc why I wasnt offered something stronger than Motrin, he said "its ok honey, you women give birth every day and dont need pain medicine, right ol sport?" and slapped my husband on his knee. After demanding to speak to the chief of ER medicine.. I finally got sent on my way with 5 hydros and a look from the doctor.

I think women complain less than men do about pain.

As for other discriminations, yes they do happen, based on income, health insurance and racial factors. its sad really. Why cant doctors be compassionate to those in pain? Other than the obvious DEA breathing down their necks