Has anyone on here supplemented a bottle for breastmilk?

Don't, its a slippery slope.

Do one or the other.

I do because I wasn't producing enough milk at first and my doctor was concerned about the baby's weight. I breast feed first and then if she's still hungry I give her a bottle. At first it was like 2 ounces after a feeding. Now because I'm back at work she gets just formula during the day and at night and early morning I breast feed and then offer a bottle. It's worked well for us because honestly sometimes I just don't have time to breast feed and it's nice knowing I can just give her a bottle.

I've been supplementing between formula and breastmilk for 7 months now and have not had any problems. I make sure to drink tons of water and take fenugreek pills as well to keep my supply up. My daughter's pediatrician is aware of this and she told me that lots of women do this. I will continue to do so until she no longer wants breastmilk.

I wouldn't. It will mess with your milk supply and it might even ruin breast feeding altogether for you. This is what happened to me. I gave my daughter a bottle one time and she never wanted to go back to the breast, then I tried pumping her supply but there was not enough milk because she was not nursing. The bottle is easier for them to use, it takes less effort. Also, I would worry about the digestion upset this may cause. The protiens are so different, you might upset your babys belly. I would choose one or the other.