i find breast-feeding makes me SO thirsty. its not too bad anymore as millie also has 3 meals solids and 1 bottle formula now i only give 4 little BFs, but when i was exclusively BFing giving about 8 big BFs a day i had 2 drink LOADS. i wouldnt be surprised if i got thru 3 or 4 litres a day back then. u can tell if ur dehydrated by looking at ur pee it should be clear not yellow, if its yellow ur dehydrated.