Dear Samschoice,

A clinician will inject the shot every 12 weeks to prevent pregnancy. Protection begins immediately if the shot is given within the first five days of your period. If not, use a backup method of birth control — like condoms — for the first week. The shot will reduce the risk of pregnancy for three months.

Used correctly and consistently, the shot is up to 99.7 percent effective against pregnancy — that's the same effectiveness rate as the pill. But remember, like the pill, the shot offers no protection against sexually transmitted infections. Only latex and female condoms reduce the risk of infection. Click here for an important update about the shot.

Hope this information helps!

Take care,

teenwire.com^® Editors

This column is for informational purposes only and is not intended to constitute medical advice, diagnosis, or treatment. If you have a medical problem, please call toll-free 1-800-230-PLAN for an appointment with the Planned Parenthood health center nearest you.