What Causes Birth Control to Fail?

By far, the most common reason birth control pills fail is improper use. You absolutely must take your birth control pills as directed or they will be less effective. If you aren’t sure you understand the directions – they can be complicated sometimes, after all – make sure you ask your doctor or pharmacist to clarify. Never assume. Assumptions really could lead to an unplanned pregnancy. Ask what you should do in case of a missed dose. Ask what you should do if you forget to get your prescription filled and run out. Ask questions to prevent coming up against a situation you haven’t prepared for and don’t know how to handle. With all that said, there are other reasons birth control pills fail. The most common reasons birth control fails are covered below.


Aside from misuse, antibiotics are probably the biggest reason birth control pills fail. If you’re sick and require medical treatment, it is very important that you’re honest with your doctor and listen to what your doctor tells you. Yes, antibiotics can cause birth control pills to fail but that doesn’t mean you should avoid them. Ask your doctor about alternatives that you may be able to take that will not interfere with your birth control pills or simply use a secondary form of birth control until you’ve completed your cycle of antibiotics. Make sure you ask your doctor about possible interactions between your antibiotics and your birth control pills so you know whether or not you need to take extra precautions.

Herbal Supplements

Herbal supplements are becoming a much bigger problem for the effective use of birth control simply because more people are choosing to use them. Herbal supplements are great and can offer a lot of health benefits but it’s important to consult with your doctor before you start taking anything, especially if you’re taking birth control pills. Some herbal supplements can cause birth control pills to fail but not all of them will. The best way to be sure whether or not the supplement you want to take is one of the supplements that cause cause your birth control to fail is to ask your doctor. If the supplement you’re interested in has been known to cause birth control pill failure, ask your doctor about alternatives you can try.


Certain illnesses have been known to cause birth control pills to fail. Most birth control pills work when the hormones in the pill are absorbed into the body. When you’re sick, especially if you’re vomiting or have diarrhea, your body isn’t able to absorb hormones as well which reduces the effectiveness of the pill. If you’re sick, you’re probably not going to feel much like having sex, but if you do, it’s a good idea to use a secondary form of birth control like a condom or a diaphragm. It’s a good idea to continue using this secondary form of birth control after you start feeling better for at least a week. It may not be entirely necessary, but it’s always better to be safe than sorry.

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