Tipping Question for US dwellars

[monster]

My friend gave me a gift certificate for a massage. I would normally tip after a massage, but this is in a doctor's office and is viewed as more "holistic medicine" than "spa" So do I tip? You don't tip a chiropractor, but then again, it's unusual to get a gift certificate for a chiropractor.

My friend is the person i would usually ask about these sort of things, but I sort of feel that asking her about this would be on a par with asking someone just how many batteries the new toy they gave you needed -sensible but tactless "thanks for the gift that's immediately costing me money" ...and she's senitive to stuff like that, so the last thing I wasnt to do is make her feel bad.

I don't mind the whole tipping thing -I'm used to it, I generally know the score, but Brit me is uncomfortable with the actual handing over cash bit and would be mortified to try and tip and be told it isn't the done thing or clearly create an awkward moment.

Your opinions, please.