You can buy Ketostix from ebay or a chemist that you wee on to test, but otherwise, not feeling hungry (physically) yukky taste in mouth and loosing weight usually means you are in ketosis any time from day 3ish onwards!!
Just wanted to add that if you decide to buy some you can cut them in half vertically to get double. I saw that tip on this forum and they work perfectly well half the size. My tub cost me around £5 from Boots. You don't need them but I do get a little thrill when I see the test turn pink and I know the science bit is working.
I must say it is one of the things that made me successful at getting back on track. I had been picking on the school holidays and having occasional meals for one reason or another and only lost a few pounds in over a month. I decided it was about time I got back on track. I bought the ketostix and tested each morning after 3 negative mornings I was delighted to get a clear positive on the fourth it was almost as exciting as a pregnancy test! After that I tested every morning and there was no way I was going to cheat and jeopardise the result. You do need to use them in the morning before the pee is diluted by all the water.