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5 things that can negatively affect the effect of the pill

The birth control pill is among the safest contraceptives. But beware, there are some things that can interfere with its effectiveness. Tikbow explains which drugs and foods can reduce protection against unintended pregnancy or harm health when combined with the pill.

How does the contraceptive pill work?

Most birth control pills prescribed to adult women are so-called micropills. In simplified terms, their mode of action is as follows: with the aid of a combination of different hormones, they prevent pregnancy in the female body, whereby an artificial surplus of progestogen, among other things, prevents an egg that could be fertilized during sexual intercourse from jumping.

The catch: various substances and other circumstances can disrupt the effect and influence the hormone release of the contraceptive pill. As a result, ovulation is no longer reliably prevented, intermittent bleeding can occur, and – even more consequential ­– contraceptive protection is no longer guaranteed for long. Tikbow asked Prof. Dr. Friedrich Wolff, specialist in gynecology, what sexually active women should know if they want to rely on the effect of their hormone pill.

Birth control pills and taking antibiotics

Various antibiotics – including. Penicillins and tetracyclines – can impair the effect of the pill, and this in various ways: The added hormones are "partly conjugated with sulfuric and glucuronic acid during the first liver passage and excreted into the intestine", explains the "Deutsche Apotheker Zeitung". In addition, antibiotics attack the intestinal flora, which can impede the absorption of the crucial hormones and thus impair the effectiveness of the pill. Nevertheless, gastrointestinal symptoms are common side effects that can also have a detrimental effect on hormonal protection (see below). Although the data on the interaction between birth control pills and antibiotics is still rather scarce, one should be aware of the possible interactions.

Birth control pills in combination with other medicines

As a general rule, if you need to take a new medicine: Find out at the pharmacy whether it is compatible with your hormone pill. If in doubt, use an additional condom. In addition to antibiotics, painkillers and medicines that stimulate digestive activity (e.g. laxatives) can also reduce the effectiveness of the pill; the same applies to sedatives, sleeping pills and antidepressants. A special warning applies to the mood enhancer St. John’s wort, which is herbal and therefore often underestimated in terms of its interaction potential.

Birth control pills for diarrhea and vomiting

Whether triggered by medicines, alcohol intoxication or poorly tolerated food: gastrointestinal complaints that develop before the expiry of six hours after taking the pill with diarrhea or vomiting can also massively impair its effect.

One-time wässriger stool is considered to be of little concern. However, if you have up to three bowel movements within one day, it is very likely that your body has not been able to absorb enough hormones before they leave it again. The following applies here: Please do not simply take another pill! Read the package insert of your contraceptive pill to find out what to do in this case and/or ask your gynecologist or pharmacy for more information.

Birth control pill and activated charcoal

If the diarrhea is due to food poisoning, activated charcoal tablets, which bind toxins and promote their removal, can help. The substances are thus virtually channelled through the gastrointestinal tract – and this also applies to what the body should actually utilize, i.e. also vitamins, minerals and any medications taken. The pill can therefore no longer work properly.

Birth control pills and certain foods

Grapefruits may be beneficial to health and rich in vitamins, but some of their ingredients compete with the active ingredients of the contraceptive pill. The same applies to certain herbal substances such as the above-mentioned St. John’s wort or alcohol; these can influence the hormone balance and thus cause the pill to lose its effect.

Various other foods should not be consumed in excess by women taking the pill. These include anything that can have a degrading effect, such as strong coffee, dried fruit, and fruits that can have a digestive effect.

Taking the pill before going to bed?

In general, it is advisable to take the pill at a late point in the day, for example as the last action before going to bed. This reduces the likelihood that something will subsequently impair its effect as much as possible. However, Prof. Wolff points out that it is easy to forget to take it after a social evening, or after a hard, long day at work. It is therefore better to take it in the early evening, if necessary with the help of a reminder.


  • Deutsche Apothekerzeitung (2018): Pill and antibiotics: How relevant is the interaction? (retrieved 08/23/2021)
  • Reller, Walter et al. (2010): Fünfzig Jahre "Pille" – Risiken und Folgen. (retrieved 08/23/2021)

With expert advice from Prof. Dr. Friedrich Wolff, specialist in gynecology.