I have noticed something about the stips ,which is why I guess they are not totally reliable. Over the last few weeks they have read very light or not at all, yet I have been losing great!
I bought some more where as I was shareing them with the DH. YES I was using most of them! Anyway, the last one on the open older bottle read negative, but the new one (freshly opened) read dark. Hmmm, guess the lose there effectiveness over time once open and exposed to the elements. (Exposing only meaning opening the container and getting out one for testing.) I keep them in the bathroom, I have read this was not a good idea.

Just wanted to point out that they can read very light or negative sometimes because of other factors.