These sticks are supposed to show that you are in ketosis, I'm presuming they would only work on a low carb diet. I tried them once, didn't show anything even though i was loosing. All I got was wet fingers.
If you are on a VLCD like Cambridge or Lighter life you achieve Ketosis. To test you are in Ketosis you pee on the ketostix and if it turns pink you are in Ketosis and burning fat.
I hope this helps