Hi Zentje
I have never used ketostix and I wouldn't bother buying them. Working within community health care settings I could probably access them for nothing but have never thought of it. They can be unreliable, in my own opinion, (when I was doing a different diet I had to do urinalysis before weigh-in) - I found that results changed according to how much I had to drink, had I drunk water just before the test, had I just had a foodpack, was I TOTM etc.
You will know because hunger subsides, sometimes feeling more energy, horrid almost metallic taste in mouth and sense of well-being.
Don't worry - you will soon be there!