You can get a prescription for the shot from a doctor or OB-GYN or at a health clinic, like Planned Parenthood. Some pharmacies offer on-site birth control consultations, so you may also be able to get the shot at your local pharmacy. Birth control websites, like Nurx, also offer birth control consultations and prescriptions for the shot online. Of course, if you get a prescription for the shot online, you'd need to inject it yourself.