Rachael, I loved to get referrals from Drs. that said the baby was not gaining weight because the mother had "skim milk". We now have classified human skim, !%, 2% and whole milk. I actually have a centrifuge machine that I would test the milk so I could show the Dr. that the mother's milk had sufficient amount of fat. I would take various samples of milk throughout the day (and yes for those smart ones out there, I would take random samples before feeding and after feeding) pool them and place in 75mm capillary tubes, seal end. Centrifuge for 10-15mins., measure fat content. Ruth Lawrence explains it also on p. 616 in her book. I used a % conversion table ie- 4%=.62cal/cc, 5%=.68cal/cc, etc. I have to say that 99% of the samples had sufficient fat content which confused many of the drs. Pat Bull, RN, IBCLC Naperville, IL (708) 420-2172