Just add a dash of Snopes.
I take a multivitamin every day, and it doesn’t have any effect on my pee, but when I drink a smoothie with a mulitvitamin booster, it turns bright yellow. Probably because I take cheap target brand vitamins.
Isaac Asimov reported that this joke had been played on HIM once in the 50s or early 60s. His report was a little self-serving (“No, I didn’t panic. I just figured it was blood and monitored how much blah blah blah”) but still pretty funny.
I’m fairly sure that you only get the bright yellow pee if you’ve taken an excess of B vitamins. If your body actually needs it and uses it it doesn’t come out in your urine and you don’t get the cool bathroom show.
That’s a good sign, it means you’re getting enough vitamins that your body can pass some. Of course, that means you’re wasting a bit of 'em, sure, but they are pretty cheap in the large scale of things. Try adding extra B-12.
True story…
I was on some strong prescription antibiotics once, and was out in this night club where the bathrooms were all lit with black lights. Well, at the urinal my urine flouresced a vivid bright green. It shone! Other people in the bathroom saw, one said ‘holy shit!’, it was quite impressive. I then started making light saber noises while streaming, moving the stream all over the urinal, and said in my best Vader voice “I am your father!” I cracked the whole restroom up and was the hero of the club.
My finest fifteen minutes of fame 
I hope you hadn’t been drinking antifreeze? Antifreeze (in urine) fluoresces(sp) under a black light.
Re: The B-vitamins causing neon yellow urine. I thought that was common knowledge. I always notice that when I take vitamins and several years ago I first noticed it when taking a B vitamin supplement. The neon glow is always helpful when I can’t remember if I took my vitamins that day, I only need to wait a while for confirmation.
Just because we are supposed to be fighting ignorance here, “fluorescence” is spelled with the u before the o. Otherwise, it’s flourescence - essence of ground wheat?
This past summer I had some pills that were supposed to treat what they thought was a UTI (it ended up being a kidney stone). They made my urine bright orange. Like traffic cone orange. It was the coolest thing ever!
This happens to me.
I gave plasma today. It had a nice yellow neon shine to it. 
I had bright orange pee as a result of medicine for a kidney infection. I gave a couple of the pills to a guy with a head cold. He was frantic for a few hours until I broke down and told him the truth.
Phenazopyradine, aka Pyridium. Sold OTC under Uristat and other names. This stuff is absolute blaze orange coming out, and I say that from experience.
Dammit. Phenazopyridine.