I so agree with above posters. I've had supply issues and at the hospital they started to measure by a 'yield test', so that's what I went by, but I later learned that the baby is more efficient than a pump and can actually extract I think it was 60% more than a pump (or thereabouts, but then again, I'm unsure how they arrived at that number). In the end, I was told to just go by wet diapers as the indication she is getting enough. For me, she ended up not getting enough by breast only, whereby I supplement with bottle at every feed. That's just my 2 cents!