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I know if you take penicillin it can lower the effectiveness of birth control but is this effect retroactive i.e. I had sex the night before going on the penicillin?

In: Birth Control, Chances of Being Pregnant, Antibiotics, Penicillin [Edit categories]

Answer:

Yes. The penicillin is in your system and will start to do its thing. This may change the effectiveness as soon as it hits your blood stream.

Contributor:

Kodiakcathy

First answer by Kodiakcathy. Last edit by Kodiakcathy. Contributor trust: 1334 [recommend contributor ]. Question popularity: 1 [recommend question].

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Does penicillin vk effect birth control pills effectiveness?
Birth ontrol pills may not work as well while you are using Penicillin-VK . To prevent pregnancy, use an extra form of birth control (eg, condoms).
Can you get pregnant on birth control and on penicillin?
well the thing is. babies aren't a fungus. so yes. penicillin isn't gonna help you much... birth control might though. talk to your doctor to see if astrozenica is right for you! :)
When does birth control take effect?
If you're referring to the birth control pill, you should use a back up method of birth control, like condoms or abstinence from vaginal sex, for the first seven days of the first pack.
Can you get pregnant if you are on birth control and had sex the night before your period?
You can get pregnant anytime. If you take your pills you should be fine. I am always very careful, checking each condom and taking my pills. Each time you have sex you increase your chances of...
Do you have to take birth control before sex for it to work?
No, in order to properly prevent pregnancy by using an oral contraceptive, you must pick a specific time to take your pill daily. It is important to take your pill everyday around the same time.