Well, it works for me. Of course, the more your urine is diluted, the less keytones there will be in it. And the more dehydrated you are , there will be more. If you use the strips, you'll see the same thing. If you have very dark purple, you are probably not drinking enough water. It's sometimes hard to tell, for me, with the strips, because I burn a lot of my keytones and drink a lot of water, thus making it harder to read the strips, as they don't always show much color even when I am in ketosis.