Do you pay your health insurance co-pay before or after you are seen by the doctor?

I just got on my husband's plan of blue cross blue shield PPO. There is a 40 co-pay with every doc visit. When I go to the doctor (I'm going for an IUD removal and to talk about other birth control options) will they ask for the money up front or after they are done? How does it happen for you? Thanks
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I believe many doctor's offices are asking for the money upfront these days to make sure they get paid their co-pay by you BEFORE you see the doctor to make sure they get their money.
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