Can Weight Loss Drugs Affect the Birth Control Pill?

Duly Care
5 days ago
6 min read

As weight loss drugs gain popularity, many women are wondering whether these medications might affect the birth control pill’s reliability.

In this blog, we explore these questions and understand what the birth control pill is, what weight loss drugs are, whether weight loss drugs interfere with the birth control pill and what to do to stay protected from pregnancy risk.

Key Takeaways:

The birth control pill is a hormonal medication taken daily to prevent an unintended pregnancy. These contain synthetic versions of the natural female hormones estrogen and progesterone.
Weight loss medications like GLP-1 receptor agonists, fat blockers, and stimulants work in different ways to reduce appetite or fat absorption. Some of them can impact how well oral medicines like the pill are absorbed.
Some weight loss drugs, especially GLP-1s, slow digestion and may reduce pill absorption. Others, like orlistat or phentermine, might cause side effects like vomiting or diarrhea, which can also lower the pill’s effectiveness.
To stay protected, it is often recommended to use backup contraception when starting or adjusting certain weight loss meds, and consider switching to non-oral methods like IUDs or implants if absorption is a concern.

What is the Birth Control Pill?

The birth control pill, also known as the oral contraceptive pill, is a hormonal medication taken daily to prevent an unintended pregnancy. It contains synthetic versions of the natural female hormones estrogen and progesterone.

There are two main types of birth control pills - combined oral contraceptive pills (COCPs), which contain both estrogen and progestin (the synthetic form of progesterone), and progestin-only pills (POPs), which contain only progestin. COCPs are the most commonly used type of birth control pill, whereas POPs are usually recommended for women who cannot take estrogen due to medical reasons.

How Effective is the Pill?

For the pill to work effectively, it must be taken correctly. That means one pill taken every day as per the pill, ideally at the same time. When taken perfectly, the pill is over 99% effective.

But here’s the catch: missing a dose, taking it at very different times each day, vomiting or having diarrhoea shortly after taking the pill can all lower its effectiveness. This is especially true for the POP, which has a much shorter time window than the COCP. If the POP is taken late by even 3 hours, the effectiveness may be reduced.

What Are Weight Loss Drugs?

In recent years, certain weight loss medications have become extremely popular. These are usually oral or injectable medications prescribed to people with obesity or overweight issues, and can help manage appetite and promote weight loss.

Some common examples include:

GLP-1 receptor agonists, such as semaglutide and tirzepatide, work by slowing down how fast the stomach empties and by reducing appetite.
Stimulant-based medications, like phentermine, suppress appetite by affecting the central nervous system.
Fat absorption blockers, like orlistat, prevent the body from absorbing some of the fat from meals.

These drugs work in very different ways, but the most well-known group that may affect the birth control pill is the GLP-1 class (brands like Mounjaro® or Ozempic®). These drugs slow down digestion, which can interfere with how well your body absorbs medications taken orally.

Do Weight Loss Drugs Interfere with the Birth Control Pill?

The answer depends on which weight loss drug is being used.

GLP-1 receptor agonists: GLP-1 receptor agonists such as tirzepatide and semaglutide slow down the stomach’s emptying time (called gastric emptying). That means the birth control pill might stay in the stomach for longer and not reach the intestines, where it is actually absorbed, fast enough or completely.
According to clinical studies, this slower digestion can lead to reduced absorption of oral medications, especially in the first few weeks when the body is adjusting to this weight loss drug. The FDA-approved label for a brand of tirzepatide explicitly advises people who use oral hormonal contraception (like the pill) to use a backup method of birth control for four weeks after starting the weight loss medication or after increasing its dose. This is because there’s a risk that the birth control pill may not be absorbed fully during this period.
Fat blockers like orlistat: These don’t interfere directly with the absorption of the birth control pill but can cause oily stools, diarrhea, or even accidental bowel leaks, which might flush the pill out of the body before it can be absorbed.
Stimulant-based drugs like phentermine: These don’t delay digestion but can sometimes cause nausea or vomiting, which may also reduce the effectiveness of the birth control pill if vomiting occurs within a few hours of taking it.

So while not all weight loss drugs reduce the birth control pill’s effectiveness directly, their side effects, like vomiting or diarrhea, can still make it less effective. Since the POP has a shorter window for correction than the COCP, the side effects and the delay in the absorption of the pill can affect the effectiveness of the POP more than the COCP.

What You Can Do to Stay Protected from Pregnancy Risk

To stay protected from the risk of unintended pregnancy while using weight loss drugs, it is advisable to adhere to the following:

If you're using GLP-1 medications, consider using backup contraception like condoms for the first four weeks after starting or increasing the dose. This allows the body to adjust and ensures the birth control pill is being properly absorbed.
If you’re on medications like orlistat or phentermine, keep an eye on any side effects. Vomiting or diarrhea within two hours of taking the birth control pill might prevent it from working, so treat that as a missed dose and follow the instructions for missed pills given on your pill pack.
For those worried about absorption, it is best to talk to your doctor about switching to a non-oral contraceptive method - like an IUD, patch, or implant - which bypasses the digestive system entirely.

Even if your weight loss drug doesn’t directly interact with the pill, being aware of these side effects can help you stay protected. Talk to your doctor to find the best method for you.

Conclusion

Understanding how different medications interact with your birth control pill is a key part of managing your reproductive health. Whether it’s due to delayed digestion or side effects like vomiting, some weight loss drugs can affect how well the birth control pill works. Being informed and proactive can help you stay confidently protected from an unintended pregnancy.

Frequently Asked Questions (FAQs)

Can weight loss itself make the pill stop working?
No, losing weight does not directly affect how the birth control pill works.
Can I use weight-loss supplements or fat burners with the birth control pill?
Most over-the-counter supplements have not been properly studied with birth control pills. Always ask your doctor before using them together.
Do birth control pills make it harder to lose weight?
Most studies show that birth control pills do not cause significant weight gain for most users. Some people may notice mild changes due to water retention or fluid shifts, but this is usually temporary. Weight changes are more often linked to factors like diet, lifestyle, and metabolism, rather than the pill itself.
Can I take the pill with other medicines for diabetes or PCOS?
Yes, many women use birth control alongside treatment for diabetes or PCOS. However, you should always let your doctor know which medicines or supplements you are taking before using the birth control pill so they can check for interactions that might affect hormone levels.

Important

This blog, including its text, images, and infographics, is for educational purposes only and not a substitute for professional medical advice. For personalised advice, always consult a doctor.