Will taking prenatal vitamins while not pregnant make your period late?

No: No it will not have any effect on the periods.

Agree w Dr Khanna: This is not a cause. Reasons for missed/late periods: low body weight, obesity, marked weight ^ or v, over-exercise, endurance athletics, breast-feeding, ^ stress, illness, eating disorders (bulimia or anorexia), anovulatory cycle (no egg released), travel, hormone irregularities, drug use, meds (i.e., birth control) or medical problems (i.e. Pcos). #1 reason is pregnancy.

No: It will not make your period late, Do a pregnancy test if you are sexually active.