Hi - This was a question that I had asked when I first joined - I ended up with quite a few pages of answers, to boot. So you might search "Hot Lemon Water" and see if that thread comes up. In the meantime, this is what I learned:
(1) YES, it has to be HOT water; something about the heat interacting with the lemon;
(2) It is best to do 8oz hot water per 1/2 lemon (fresh - and use the WHOLE half of the lemon, not just the juice - there are oils in the skin of the lemon that lend to the cleansing effect)
(3) do the water in the morning, before you eat/drink anything, helping to exaggerate the "cleansing" effect (this is from my dr)
Good luck! If you put "hot lemon water" in your web browser, you'll be shocked at the pages come up touting the health benefits of HLW.
Becca - on LAWL (now "PURE WEIGHT LOSS as of 9/07) since 4/1/2007