Help me im confused

Patient: Im 18 and I took my first depo shot and before it kicked in I had sex now I missed my period and still haven’t got it so I took a pregnancy test and it was negative should I get blood work just in case?

Doctor: Thank you for your query.Depo Provera shot is 99% effective in preventing a pregnancy. It is made up of a hormone si milar to progesterone produced naturally in the body. Each shot provides protection against pregnancy for up to 12 to 14 weeks. Preferably it should be received once in 12 weeks to be totally protected. Birth control with provera begins immediately after the first shot is given within the first five days of the menstrual cycle. This shot can by itself lead no periods at all or irregular menstrual periods. It is better you opt for a blood for βhCG, which is more sensitive and can detect quantitatively low levels of the hormone produced coinciding with early pregnancy.Hope that answers your query. Have a good day.