I have never had any urine changes when doing henna, and I leave mine on for around 6 hours. I only us body art quality henna, I am wondering if the henna was contaminated, or maybe it was something you ate or drank?
FYI, I buy my henna from Henna Sooq. I have ordered from Mehandi.com as well, but I have fallen in love with the Red Raj from Henna Sooq. They have the best customer service, reasonable shipping, and quality products. I have emailed them with questions many times, and the owner responds within 24 hours! Now that is good customer service.
Henna!!! Red Raj from Henna Sooq
Co-washes: ABBA Pure Gentle (HG), Tresseme Naturals.
Low-poo: Shea Moisture (all of them), Renpure my pretty hair is parched.
Rinse-out: Tigi Bead Head Moisture Maniac, GF Length and Strength.
Leave-in: ABBA Pure Gentle, KCKT, Henna Sooq cocoveda oil.
Stylers: Fairy Tales Curly Q's gel (HG), KCCC, Shea Moisture curl enhancing smoothy, GF pure clean gel.