There are two types of IUDs: hormonal and copper. "An IUD that delivers hormones similar to birth control pills will take effect right away, if you get it inserted within seven days of starting your period," Savita Ginde, MD, vice president of medical affairs at Stride Community Health Centre and former chief medical officer of Planned Parenthood of the Rocky Mountains, told POPSUGAR. Otherwise, you should use a backup method of contraception for a week after the procedure.
The copper (or non-hormonal) IUD works differently and takes effect right away. "[A copper IUD's] presence in the uterus causes a sterile inflammatory reaction that can kill and impair migration of sperm and impair fertilization and implantation," explained M. Kathleen Borchardt, MD, an ob-gyn at Houston Methodist Hospital. In fact, a copper IUD can also be used as emergency contraception, as long as it's placed in the uterus within five days of a patient having unprotected sex.
Of course, there are exceptions when it comes to how long it will take for any form of birth control to work. Dr. Ginde stressed the importance of having a conversation with your healthcare provider to weigh the risks and benefits of an IUD. For example, if you have a copper allergy or Wilson's disease — which causes the body to hold too much copper — the copper IUD isn't for you.
Likewise, if you regularly take medication for a physical or mental health condition, you should speak with your doctor to ensure that it won't interfere with the overall effectiveness of an IUD. "There aren't many medications that you need to avoid if you're using a hormonal IUD," Dr. Ginde told POPSUGAR. "But some could include certain antibiotics, HIV medications, St. John's Wort, and some anti-seizure medications." If you take any of these, work with your doctor to ensure that an IUD is the most effective long-term solution.