I don't know for sure, but I read that Niacin can clean you out in a few days, if you take allot of it (2000mg. daily) and drink allot of water. But in one day? All I can tell you is shit in one hand and wish in the other.
Niacin basically just keeps your pee yellow when you flush.
I had like barely any weed from a bowl and I only got high for like 4 hours, this is now 3 days in and i have a drug test tomorrow! This was something i wasn't told until after i smoked! I dont smoke much at all. (5 months and then this one time) will i be clean or should i dilute. (Cant afford or have time to buy synthetic)
I used to have my captains licence. I've passed a lot of urine screens. I had to smoke here and there in those days. Worst/best 10 years of my life.
Timing is everything. The conservatory would watch me pee so synthetic wasn't an option. I had to make it to a conservatory and screen in 24 hours from finding out so I took a few when I found out and a few the next morning. Don't take too much or it will flush your skin not your pee and turn you all red. Too much will also make your pee bright yellow.
The morning of you wanna pee a few times. Definitely don't give them any of that morning piss. Key is piss like an hour or so ahead of time. Hopefully the niacin makes your pee just yellow enough. I also am skinny, have a high metabolism, and very active. Acting casual and not being anxious can go a long way too. I kinda gave the nurse a hard time in a good way usually too. I once said: you won't tell the other girls about my incredibly small penis will you? Haha we were friendly by then and she was flirty. She might not have even looked at the results? It didn't go back to the lab unless you failed the dip test she administered .
If it's a mouth swab they do those where I work now. They are so cheap no one really passes or fails the weed part. Everyone gets a really light line so they don't really look at it. They are more worried about meth/heroin.