Ketostix are crap. Don't use them. If you're following the diet, you will NOT fall out of ketosis. If you drink the right amount of water, you won't register on the stick. If your body has adjusted to the diet, you won't register on the stick.
I have been in ketosis for 3 months, and have NEVER registered on the stick, not once even in the beginning. Stop worrying about it and throw out the sticks and just stick to the plan. It works.