I recently failed a UA for THC and I had not smoked any I n what should've been a long enough time to be out of my system. I recently started exercising though and my levels had been going down until I started the exercise. Suddenly the levels spiked up. Exercising is the only change I've made beside the abstaining from marijuana use. Now I have a PV and will most likely be in jail when I know for a fact I have not been using the stuff.