Beeturia

Yesterday, I used a beet in some of my juice and peed red. It's happened before but I never really paied much attention to it.
Is this because of anemia? Could you explain the other possibilities?
I read up on the issue but couldn't really understand how I'm supposed to know exactly what it was that allowed me to pee red. I also recall reading that only a small percentage of people will even be able to pee red after drinking beet juice.

I also read something about low B-12...
I'm vegan with the exception of every now and then eating vegetarian burgers that contain milk or eggs (by accident)

I have some powdered wheatgrass supplement that I just add water to. Would that help?