What are the potential risks and interactions between GLP-1 (Glucagon-like peptide-1) therapy and birth control medications?

GLP-1 Therapy and Birth Control: Patient Disclaimer

Patients taking GLP-1 medications (liraglutide, semaglutide, tirzepatide) can safely use hormonal birth control without significant reduction in contraceptive effectiveness, but must use reliable contraception to prevent pregnancy while on these medications due to insufficient safety data in pregnancy. 1, 2, 3

Critical Contraception Requirement

All patients of reproductive potential must use effective contraception while taking GLP-1 medications. 4, 3

• GLP-1 therapy can restore fertility in women with polycystic ovarian syndrome or obesity-related oligomenorrhea, leading to unplanned pregnancies 3
• There is insufficient human data to determine pregnancy safety, and animal studies have shown potential adverse fetal outcomes including decreased fetal growth, skeletal anomalies, and embryonic death 3
• Patients should discontinue GLP-1 therapy at least 2 months before planned conception 3

Birth Control Effectiveness with GLP-1 Medications

GLP-1 medications do NOT significantly reduce the effectiveness of hormonal contraceptives. 1, 2, 5

Oral Contraceptives (Pills)

• Liraglutide does not reduce bioavailability of ethinyl estradiol/levonorgestrel; the contraceptive reaches peak levels approximately 1.5 hours later but maintains equivalent overall exposure 1
• Semaglutide (both injectable and oral) does not reduce ethinyl estradiol levels and causes only a 20% increase in levonorgestrel exposure, which does not compromise contraceptive efficacy 2, 5
• The slight delay in absorption does not require dose adjustments or backup contraception 1, 2

Other Hormonal Methods

• Contraceptive patches, vaginal rings, implants, and intrauterine devices are NOT affected by GLP-1 medications 6
• These methods do not rely on gastrointestinal absorption and therefore bypass any potential interaction with delayed gastric emptying 6

Important Timing Considerations

Take oral contraceptives at consistent times, preferably separate from GLP-1 injection timing by several hours if possible. 1

• While not required for efficacy, this may minimize any gastrointestinal side effects 1
• GLP-1 medications delay gastric emptying, which slightly delays but does not reduce contraceptive hormone absorption 1, 2

Medications That DO Reduce Birth Control Effectiveness

Be aware that certain other medications significantly reduce contraceptive effectiveness and require backup methods. 4, 7, 6, 8

Enzyme-Inducing Medications (Require Backup Contraception)

• Rifampin/rifabutin: Use barrier methods (condoms) during treatment and for one full menstrual cycle after completion; consider switching to copper IUD or DMPA injection 7
• Anticonvulsants: Phenytoin, carbamazepine, barbiturates, primidone, topiramate, oxcarbazepine reduce contraceptive efficacy 6
• St. John's Wort: Herbal supplement that significantly reduces contraceptive hormone levels; use barrier methods or switch to IUD 8
• Some HIV medications: Ritonavir-boosted protease inhibitors may reduce contraceptive efficacy 4, 6

Medications Safe with Birth Control

• Broad-spectrum antibiotics (except rifampin) do NOT reduce contraceptive effectiveness 6
• Antifungals and antiparasitics do NOT interact with contraceptives 6

Gastrointestinal Side Effects Warning

Nausea and vomiting from GLP-1 medications may compromise oral contraceptive absorption if severe. 4, 9

• Nausea occurs in approximately 40% of patients on liraglutide and is common with all GLP-1 medications 4
• If vomiting occurs within 3-4 hours of taking oral contraceptives, use backup contraception (condoms) for 7 days 4
• Consider non-oral contraceptive methods (patch, ring, IUD, implant) if experiencing persistent severe nausea 4
• Gastrointestinal side effects typically decrease over time with gradual dose titration 4

Pregnancy Testing Requirements

Obtain a negative pregnancy test before starting GLP-1 therapy. 4, 3

• Test for pregnancy if you miss a menstrual period while on GLP-1 therapy 4
• Discontinue GLP-1 medication immediately if pregnancy is confirmed 3
• Contact your healthcare provider if you suspect pregnancy 3

Special Populations Requiring Enhanced Contraception

Women with obesity taking phentermine-topiramate combinations must use highly effective contraception due to teratogenic risk. 4

• Topiramate causes birth defects and also reduces contraceptive effectiveness 4
• This combination requires consistent use of effective contraception throughout treatment 4

Emergency Contraception Considerations

Emergency contraception can be used if needed while taking GLP-1 medications. 4

• Levonorgestrel emergency contraception (Plan B) can be taken without interaction concerns 4
• Ulipristal acetate (Ella) requires waiting 5 days before resuming hormonal contraception 4
• Copper IUD insertion is the most effective emergency contraception option and unaffected by any medications 4

Key Disclaimer Points for Patient Education

Your GLP-1 medication (liraglutide/Saxenda, semaglutide/Wegovy/Ozempic, tirzepatide/Mounjaro/Zepbound) does not reduce birth control effectiveness, but you MUST use reliable contraception because:

• These medications may restore fertility if you previously had irregular periods 3
• Safety in pregnancy is unknown with insufficient human data 3
• Unplanned pregnancies have occurred in women taking these medications 3
• You should stop GLP-1 therapy at least 2 months before trying to conceive 3

Your birth control will work effectively with GLP-1 therapy, but:

• Severe vomiting may reduce oral contraceptive absorption—use backup methods if this occurs 4
• Certain other medications (rifampin, some seizure medications, St. John's Wort) DO reduce birth control effectiveness 7, 6, 8
• Non-oral methods (IUD, implant, injection, patch, ring) avoid any absorption concerns 4, 6

Contact your healthcare provider immediately if:

• You miss a menstrual period 4
• You experience severe persistent vomiting 4
• You start any new medications, especially antibiotics or seizure medications 7, 6
• You suspect you might be pregnant 3