My period is 8 days late why is that?

Could be pregnant. One of the most common reasons for a late period is pregnancy. You should consider taking an at-home pregnancy test or seeing a doctor.
Depends. If you are sexually active, a very common reason is that you could be pregnant. Checking a home pregnancy test usually will answer that question for you. If it is negative, or you are not sexually active, it could be that you did not ovulate, or release an egg, from your ovaries in the past month. If you are on birth control, it could be a normal side-effect.

Related Questions

I just had my first period in 7 months post pill from progesterone cream.1st cycle I bled. 2nd cycle on progesterone &my period is 8 days late. Why?

Rule out pregnancy. If you are not pregnant,then perhaps you need a work up if you haven't had one to find out the reasons for your irregular periods. Read more...