Currently, we find several types of contraceptives for women, such as hormonal contraceptives that prevent unwanted pregnancy by blocking ovulation. Besides the ones popularly known as the “pill,” there are other technologies and forms of administration available on the market. In general, the different options include:

These days, side effects are also minimized1, especially since many options now use lower hormone doses. Still, each body reacts differently to the different types of contraceptives, and there are certain contraindications, such as in cases of diabetes or a family history of thrombosis. For this reason, it’s always very important to consult a gynecologist when making your choice. For those wanting to clear up some doubts right away, it’s worth checking the content below.

When Does Birth Control Start to Work?

Usually, oral contraceptive pills begin to work from the first pill of the first pack or, in the case of the injection, from the first contraceptive injection. But be careful, as this only applies if taken on the first day of your period, following standard usage recommendations, and for those who menstruate regularly. The explanation is that the hormones estrogen and progesterone reach a “safe” level in the body after the first week of use and, as this coincides with the first week of the menstrual cycle, the risk of ovulating before reaching this level is almost nil2. Anticipating non-compliance with this rule and cases of women with very short or irregular cycles, some doctors recommend the use of other barrier methods such as condoms, for example, during the first month on birth control. It’s also important to clarify that the first day of your period is considered the day the flow comes “for real,” not just a spotting or stain before your period.

How to Know if Birth Control Is Working

There are no symptoms that guarantee that birth control is working at the moment. Ideally, do not forget doses and use other contraceptive methods if you miss a pill, feel sick, or take any medicine that may interfere with the effectiveness of birth control.

How to Know if Birth Control Is Not Working

Birth control is ineffective if it is expired, not taken properly, not digested due to gastrointestinal problems, or if there are interactions with other medications. There are no specific symptoms that could indicate it did not work. Remember that spotting is common when taking birth control, but does not indicate loss of effectiveness.

What Can Affect the Effectiveness of Birth Control

In the case of the pill, if you forget to take a dose for more than 12 hours after the usual time, the effect may be compromised. Furthermore, if you have diarrhea or vomiting within 3 hours after taking the pill, its effectiveness may also be compromised. Finally, certain medications can also interfere, as we will see below.

Medications and Drugs That Affect Birth Control Effectiveness

Research related to interactions is still being developed3, but so far what is known is that certain drugs such as antibiotics, anticonvulsants, barbiturates, antiretrovirals, and anabolic steroids can affect the effectiveness of birth control. See which drugs decrease the effectiveness of hormonal contraceptives:

Antibiotics: Rifampicin, Ampicillin, and Tetracycline.
Antiepileptics and anticonvulsants Carbamazepine and Oxcarbazepine, Topiramate, Diphenylhydantoin, Primidone, Phenobarbital, and Phenytoin.
Antifungals and antiprotozoals Griseofulvin
Antiretrovirals Efavirenz, Nelfinavir, Ritonavir, and Nevirapine
Diuretic for hypertension Spironolactone
Herbal medicine St. John’s Wort

What Can Affect the Effectiveness of Injectable Birth Control

In the case of injectable birth control, only drug interactions can reduce contraceptive effects, since there is no risk of forgetting or not digesting.

Is It True That Antibiotics Affect the Effectiveness of Birth Control?

The studies and theories suggesting some antibiotics may affect the effectiveness of birth control are still not a consensus among specialists, since there is no 100% evidence of this correlation. The hypothesis is that eliminating certain intestinal bacteria could interfere with contraceptive effects. In any case, it’s always better safe than sorry, right?

List of Antibiotics That May Affect the Effectiveness of Birth Control

The types of antibiotics that could compromise the effectiveness of birth control are:

  • Rifampicin
  • Ampicillin
  • Tetracycline

How to Stop the Effect of Birth Control

For those wanting to become pregnant and stop using birth control, the recommended way is to stop taking the pill after the last pack. This way, there will be a period and the cycle will restart with the woman able to ovulate. When you stop birth control in the middle of a cycle, hormones can become unbalanced and lead to side effects. For some women, it may take months for the cycle to regulate and increase the chances of getting pregnant.

When Does Birth Control Lose Its Effect?

Continuous use of birth control does not make it lose effectiveness. The only 3 possible reasons birth control loses its effect are:

  • Forgetting doses
  • Vomiting or diarrhea after taking the pill
  • Concurrent use of certain medications

Also See: Side Effects of Contraceptive Methods