Can not having a period for a year cause abnormal cells in the uterus should i ask for a smear test? i'm only 17 years old.

Confusion re problem: you are confused with regard to causes of not having a period. Primary amenorrhea describes post-pubertal women without their first period. Women whose periods have stopped have secondary amenorrhea. In young women (yours dates to age 16) the cause may be intense physical conditioning, or other causes, but not "abnormal cells in the uterus. Please obtain a gynecological examination.

Very unlikely at 17: The possibility that "not having a period for a year would cause abnormal cells in your uterus at age 17" is quite small/and may be so minimal and so remote as to be negligible unless you are markedly overweight, obese exposed to unopposed estrogens or perhaps have a genetic predisposition to uterine, breast, ovarian or colon cancers.