What are some things that can cause you to have a late period?

Many causes inc PCOS: Pregnancy or early miscarriage! a one-off late period can be caused by stress or ovarian cysts. Long or irregular cycles can be due to polycystic ovarian sydrome (pcos), also thyroid problems, excess prolactin hormone, aging of the ovary (diminished ovarian reserve), or low hormone levels (hypogonadism) from heavy exercise, eating disorders, or stress. Some medications can affect your cycles.

Late: 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.