How GLP-1s Impact Birth Control
By April Hopcroft
Because GLP-1 receptor agonists slow down digestion, they may delay the absorption of oral medications like birth control pills, which could affect ovulation and fertility.
As more people begin taking GLP-1 receptor agonists and other incretin-based drugs for glycemic control and weight management, new side effects of these treatments (both good and bad) are emerging.
Looking at the positives, a large trial of over 17,600 adults found that Wegovy reduced the rate of cardiovascular events, including heart disease and stroke, by 20%. This trial led the FDA to expand Wegovy's label to include reducing cardiovascular risk in people with obesity.
On the negative side of things, the FDA updated the label for Ozempic with a warning about intestinal blockages after multiple reports of the rare but severe side effect.
Now there is concern about whether GLP-1s may interact with birth control pills.
Because GLP-1 medicines slow digestion, they may affect the absorption rate of other oral drugs. By slowing the rate at which food travels through your digestive system, they could potentially delay the absorption of the hormones in birth control pills, which could affect ovulation and fertility.
We spoke with Dr. Claire Meek, a consultant in the diabetes in pregnancy service at Addenbrooke’s Hospital and principal investigator at the Institute of Metabolic Science at the University of Cambridge in the U.K., to explore how GLP-1s affect oral birth control.
Do GLP-1s impact how well birth control pills work?
Overall, research on GLP-1s and birth control is “very sparse,” Meek said. On one hand, Meek said some studies conducted by drug companies have found no evidence that GLP-1s affect birth control absorption.
For instance, a 2015 study found that Ozempic (semaglutide) did not affect the levels of oral birth control available in the bloodstream. The study was small (just 43 women) and lasted for about 23 weeks.
However, Meek said she has received reports from patients about issues with GLP-1s and birth control. Indeed, a 2023 case study described a woman with type 2 diabetes who became pregnant while taking Mounjaro (tirzepatide) and birth control pills. More recently several women have taken to social media to document their experiences becoming pregnant after starting weight-loss drugs like Ozempic.
The interaction between GLP-1s and birth control is unclear
One key problem is that the process by which GLP-1s reduce the effectiveness of birth control isn’t well understood.
It’s possible that the weight loss caused by GLP-1s improves fertility, which leads to higher rates of pregnancy.
Excess weight is known to reduce fertility. In addition to the estrogen already made by the ovaries, fat cells also produce estrogen. When estrogen levels are too high, this tricks the body into thinking it's pregnant and prevent ovulation.
Losing weight can help restore normal levels of estrogen production to support ovulation and pregnancy. In fact, research has shown that women with overweight or obesity who participated in weight loss programs were more likely to become pregnant than those who did not undertake weight loss interventions.
“In the longer term, prolonged use of GLP-1 agonists appears to vastly improve fertility, even in people who previously considered themselves infertile,” Meek said.
Preliminary research suggests that GLP-1s may improve menstrual regularity and increase fertility rates among people with obesity with hormonal disorders like polycystic ovarian syndrome (PCOS). For example, the GLP-1s Saxenda or Victoza (liraglutide) have been found to improve fertility, especially among people with PCOS.
It’s also possible that GLP-1s directly reduce the absorption of hormonal contraceptives by delaying gastric emptying, as stated on Mounjaro’s drug label.
Meek said it’s important to consider how consistently you’re taking birth control. Oral contraceptives are most effective at preventing pregnancy when taken every day. However, in real life, people may miss a pill here and there.
One theory is that a missed dose of birth control has different effects depending on your body weight. If you’ve lost a significant amount of weight and you miss a birth control pill, it may have a greater effect on improving fertility than a missed pill would have on someone with a higher body weight.
“It’s quite possible that missing a dose of birth control is more likely to result in pregnancy when you’re on a GLP-1 agonist, as substantial weight loss with improved glucose levels will improve fertility,” Meek said.
“It's a very different situation to missing a dose when you have obesity, insulin resistance, and hyperglycemia, which all reduce fertility,” she added.
Key considerations for taking a GLP-1 and oral birth control
Currently, the drug labels for GLP-1s do not include recommendations regarding birth control pills.
However, the FDA states that Mounjaro – a dual GIP/GLP-1 receptor agonist – may reduce the efficacy of oral birth control due to delayed gastric emptying. According to the drug label, Mounjaro is most likely to reduce birth control efficacy after the first dose, with this potential side effect diminishing over time.
Monitor side effects
It’s common to experience side effects for both GLP-1s and birth control pills when starting either medication.
Adverse reactions to GLP-1s tend to be gastrointestinal, including symptoms like nausea, vomiting, and diarrhea. Side effects of birth control include nausea, breast tenderness, headaches, changes in your period, weight gain, and mood changes.
“Starting a medication, there will be a period (often 2-4 weeks) when you’re getting used to any side effects,” Meek said. “There can be nausea, vomiting, and changes to gut transit, which can influence the absorption of birth control.”
After starting a GLP-1, Meek said healthcare providers should help you monitor side effects. It’s important to recognize that side effects could also arise from interactions between GLP-1s and any medications you take for other conditions.
Call your healthcare provider right away if you experience serious side effects, such as severe stomach pain, chest pain, new or worsening headaches, blurred vision, fever, severe hypoglycemia, or dehydration after starting a GLP-1 or birth control.
Use additional protection when starting or increasing GLP-1 doses
If you just started taking a GLP-1 and are on birth control pills, you may want to add a second type of contraceptive to prevent pregnancy.
For instance, Mounjaro’s label recommends that people taking birth control pills “switch to a non-oral contraceptive method, or add a barrier method of contraception for four weeks after initiation and four weeks after each dose escalation.”
While GLP-1 drug labels do not contain specific recommendations about birth control, you may still want to consider extra protection for peace of mind. This could include a birth control injection, implant, patch, vaginal ring, IUD, or condoms.
Switch to a long-acting reversible birth control
Meek said she encourages planned pregnancies, rather than unplanned pregnancies, for any person with diabetes.
Diabetes adds another layer of complexity to pregnancy and increases the risk for serious complications, such as high blood pressure, low blood sugar, and life-threatening birth defects for the baby. Therefore, it’s crucial to plan ahead and work on lowering your A1C and increasing time in range before conceiving.
“In general, people with any type of diabetes who are not planning a pregnancy are recommended to be on long-acting reversible contraception,” Meek said.
Examples of long-acting birth control options include an IUD or hormonal implant. These methods last for several years, provide excellent protection against pregnancy, and can be removed at any time.
Can GLP-1s harm a pregnancy?
The drug labels for Ozempic, Rybelsus, Wegovy, and Mounjaro all acknowledge that these medications could potentially impact fertility or harm a developing fetus.
Meek said there’s not a lot of evidence that GLP-1s cause harm to a fetus, but some animal studies have shown the possibility.
“We’re still unclear of the risks of GLP-1 agonist use in human pregnancy, and therefore the most cautious approach is to make sure that a GLP-1 is stopped well in advance of trying for pregnancy,” Meek said.
Researchers are continuing to investigate the safety and efficacy of GLP-1s in pregnancy. Novo Nordisk is conducting a clinical trial to study safety outcomes of infants born to pregnant people exposed to Wegovy and other weight loss medications during pregnancy. Novo Nordisk has also created the Wegovy Pregnancy Registry for both medication users and healthcare providers to report pregnancies that have occurred while taking Wegovy.
The bottom line on GLP-1s and birth control
Having an individual conversation with your healthcare provider is key to ensure you’re meeting your diabetes and reproductive health goals.
“I consider GLP-1 agonists a really valuable part of women’s care before and after pregnancy,” Meek said.
Overall, it’s important to examine risks and benefits for each person individually. It’s also important to consider how risks and benefits may change during transitions from pregnancy prevention and preconception planning to pregnancy and postpartum.
For anyone with diabetes who is considering becoming pregnant in the future, Meek recommends using preconception care to plan for a healthy pregnancy. Pre-pregnancy services are especially important for people with type 2 diabetes, Meek said, as many have had diabetes for a shorter period and might not know that they’re eligible for such services.
Ultimately, improving reproductive health for people with diabetes is a matter of “changing conversations to make sure women can access the support and education they need both pre- and post-pregnancy,” Meek said.
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