They sell ketostix at most pharmacies. They are strips of ph style chemical that you use like a pregnancy test. Wait the allotted time (15 seconds for most) and it will tell you if you are producing keytones, how many there are, etc. Most people check in the morning, when keytones are most present.

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As for average loss... I don't have one! I lost 14lbs during the first 2 weeks, then 10lbs/month for the next to months, then nothing for the next 3 weeks, now though - I've lost 3lbs since Wednesday. *shrug*