What reduces birth control efficacy?

Hormonal birth control methods prevent pregnancy by regulating ovulation, thickening cervical mucus, or inhibiting sperm production.

Common examples of female hormonal birth control methods include:

• combined oral contraceptives (COCs): norgestimate ethinyl estradiol and levonorgestrel and ethinyl estradiol
• progestin-only pills: norethindrone (Ortho Micronor) and levonorgestrel
• contraceptive patches: ethinyl estradiol and norelgestromin (Xulane)
• hormonal intrauterine devices: levonorgestrel (Mirena)
• hormonal implants: etonogestrel (Nexplanon)
• injectable contraceptives: medroxyprogesterone acetate (Depo-Provera)

Male hormonal contraception options are currently limited, but ongoing research includes testosterone injections and gels.

 Some medications, foods, supplements, and behaviors may lower or cancel out the efficacy of birth control.

Supplements that may interfere with birth control methods

Although possible, interactions between hormonal contraceptives and supplements are rare. However, different factors, like the type of contraception, may have an effect.

You’re encouraged to let your healthcare professional know about all the supplements you take or plan to take.

Supplements that may interfere with birth control methods include:

• St. John’s wort: This herbal supplement may reduce the effectiveness of hormonal birth control methods by affecting how your body produces and uses progestin and estrogen in the liver.
• Alfalfa: This supplement may reduce the efficacy of birth control due to its potential to increase liver enzyme activity. This can lead to the faster breakdown of contraceptive hormones, which may affect how long they stay in your body. 
• Saw palmetto: Often used for prostate health and hair growth, this supplement may affect hormone levels.

If you take these or other supplements, you may consider using additional contraceptive measures, such as condoms.

Consider talking with a doctor before starting any new supplement while taking hormonal birth control. Doctors can provide guidance on potential interactions, suggest alternative contraceptive methods if needed, or provide a schedule likely to reduce interactions.

Medications that may reduce birth control efficacy

Nonprescription and prescription medications may affect hormonal production and balance and reduce the effectiveness of hormonal birth control methods.

Medications that may interact include:

• Antibiotics: Some antibiotics, like rifampin (Rifadin) and certain penicillins.
• Anticonvulsants: Medications prescribed to treat seizures, such as phenytoin (Dilantin), carbamazepine (Tegretol), and topiramate (Topamax).
• Antifungals: Certain antifungal drugs, like ketoconazole (Extina), griseofulvin (Gris-PEG), miconazole, terbinafine, and clotrimazole.
• Antiretrovirals: Medications used to manage HIV and AIDS, including protease inhibitors such as lopinavir ritonavir (Kaletra), and non-nucleoside reverse transcriptase inhibitors (NNRTIs) such as efavirenz (Sustiva).
• NSAIDs: Although rare, some nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and aspirin may lead to adverse interactions and increase the chance of blood clots.

This is not an all-inclusive list, and drug interactions may depend on different factors, most of which you may be able to manage.

Consider providing your healthcare professional with a complete list of medications you take before starting a new hormonal birth control method. They can advise you about potential interactions and discuss alternative methods of contraception if needed.

In some cases, adjusting the usage timing or prescription drug dosage may help minimize drug interactions.

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Foods that affect birth control methods

While most foods do not directly cancel out hormonal birth control, some may indirectly lower their effectiveness. These include:

• Grapefruit: Grapefruit and its juice may interfere with how your body metabolizes medications, including birth control pills. 
• High fat meals: Consuming a high fat meal while taking some birth control methods, like COCs, may slow absorption rate and effectiveness.
• Alcohol: While alcohol does not directly affect birth control effectiveness, high alcohol consumption may lead to forgetfulness or inconsistent usage of birth control methods, which makes them less effective.

Other factors that may affect hormonal birth control

Other factors that may make hormonal birth control less effective include:

• Inconsistent usage: Forgetting to take a pill at the same time every day or skipping a day may make it less effective.
• Vomiting or diarrhea: If vomiting or severe diarrhea occurs within a few hours after taking the pill, its absorption may be affected, reducing its effectiveness. Using an alternative contraceptive method, like condoms, is recommended.
• Storage conditions: Exposure to extreme heat, moisture, or light conditions that do not follow storage recommendations may affect the potency of hormonal contraceptives.  
• Weight and BMI: Reviews from 2018 and 2016 suggest that some emergency contraceptives and combined hormonal patches may be less effective in people with obesity. 

Summary

Hormonal birth control methods effectively prevent pregnancy when used according to medical recommendations. However, some factors may reduce their efficacy. These include inconsistent usage, vomiting or severe diarrhea, and drug interactions. 

Consider discussing your concerns and going over birth control instructions and interactions with your healthcare professional.

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