Prenatal vitamins causing thirst?

Heather
I've started to take prenatals since about two weeks ago. My husband and I are TTC and recently had a BFN, so I'm pretty sure that what I've experienced isn't due to pregnancy. Since starting the prenatals, I've noticed that my mouth feels drier and that I'm often thirsty,m. Because of this, I use the bathroom much more often. 
Is this common/normal? I did a search on Google and can't get a straight answer.