How GLP-1 Drugs May Affect Common Medications, According to Doctors

Weight-loss medications in the GLP-1 class, such as semaglutide (Wegovy) and tirzepatide (Zepbound), have become widely recognized for helping people lose weight by slowing how quickly the stomach empties and reducing hunger. But that same effect can also change the way the body absorbs and reacts to other medicines.

The encouraging news is that, in many cases, these interactions can be managed with medical supervision and dose adjustments, says Caroline Apovian, MD, director of the Mass General Brigham Weight Center and a professor of medicine at Harvard Medical School. Some newer research even suggests that certain pairings, including hormone therapy (HT) and GLP-1 drugs, may improve weight-loss results.

If you take a GLP-1 medication, here is what doctors say you should know about its possible interactions with common prescription and over-the-counter drugs.

GLP-1s, Birth Control, and Hormone Therapy

GLP-1 medications, especially tirzepatide, have been shown to affect how oral contraceptives are absorbed, which may make them less reliable. “To be safe, we recommend that patients who take both medications follow what we call the four-week rule,” says Dr. Apovian. That means using another form of contraception, such as condoms, for four weeks after starting a GLP-1 and for four weeks after each dose increase. Methods that bypass the digestive system, such as the birth control patch or vaginal ring, do not appear to raise the same concern, she adds.

For hormone therapy, there are no published studies proving whether GLP-1 drugs affect absorption, says Stephanie Faubion, MD, director of the Mayo Clinic Center for Women’s Health. The assumption, she explains, is that oral hormone therapy could be affected because gastric emptying is slower, while transdermal options would not be. “I’d recommend any woman who is on a GLP-1 drug or plans to go on a GLP-1 drug use the transdermal patch, gel, spray, or ring to be safe,” she says.

Some early research also points to possible benefits from combining GLP-1s and hormone therapy. A study coauthored by Dr. Faubion and published in The Lancet Obstetrics, Gynaecology & Women’s Health found that postmenopausal women using HT lost 35 percent more weight on tirzepatide than those using the weight-loss drug alone. Another study in Menopause found similar results among postmenopausal women taking semaglutide (Wegovy) along with HT.

Dr. Faubion notes that these were small observational studies and that more research is needed. Still, she says the findings suggest the two treatments may work together to support better weight-loss outcomes. One theory is that estrogen may help curb appetite, support metabolism, and improve the body’s ability to build lean muscle. Better sleep from menopausal hormone therapy may also make healthy habits, such as exercise and diet changes, easier to maintain, she adds.

GLP-1s and Medications for Ongoing Health Conditions

If you take medication for hypothyroidism, heart failure, atrial fibrillation, high blood pressure, or type 2 diabetes, it is important to discuss it with your doctor, advises Dr. Apovian. Your treatment plan may need to be adjusted for the following drugs:

• Levothyroxine for hypothyroidism. Patients with hypothyroidism who start a GLP-1 often see a significant drop in thyroid-stimulating hormone (TSH), which can mean they need less thyroid hormone, says Dr. Apovian. She recommends checking thyroid hormone levels every 8 to 12 weeks while on a GLP-1 to confirm the levothyroxine dose is still right.
• Digoxin for heart failure or atrial fibrillation (AFib). Because people with type 2 diabetes, obesity, or both are at increased risk for heart failure, these drugs may be used together, Dr. Apovian says. But some research suggests GLP-1 medications can raise digoxin levels in the blood, increasing the risk of toxicity, which can be dangerous. In some cases, a clinician may choose to switch to another heart medication, such as a beta-blocker or ACE inhibitor.
• Blood pressure medications. People taking blood pressure medicine while on a GLP-1 may be more likely to develop hypotension, or low blood pressure, which can cause dizziness or fainting, according to a Northwestern Medicine study of more than 42,000 adults presented at the Endocrine Society’s annual conference. As weight falls, blood pressure often drops too, explains Talia Diker Cohen, MD, PhD, an endocrinologist at the Rabin Medical Center in Israel. She suggests discussing home blood pressure checks with your doctor to see whether a lower dose is needed.
• Diabetes drugs like metformin. If you already take metformin for prediabetes or type 2 diabetes, your doctor may keep you on it when you begin a GLP-1. The medicines can be used together safely, but studies suggest the combination may increase gastrointestinal side effects such as nausea and diarrhea. Blood glucose should also be monitored every three to six months to make sure levels do not fall too low over time, says Dr. Apovian. If the combination is not tolerated, your doctor may decide that you should stay on only one of the medications.

GLP-1s and Common Pain Relievers

If you take acetaminophen for a headache or sore knee, do not be surprised if relief is slower than usual. Dr. Diker Cohen says research shows acetaminophen can take longer to absorb because GLP-1 drugs delay gastric emptying.

The medicine will still work; it may simply take more time. The concern, she says, is that someone who does not feel relief right away may take extra doses, increasing the risk of side effects or toxicity. For that reason, it is best not to take another dose too soon.

Comparable studies on over-the-counter NSAIDs such as ibuprofen (Advil) and naproxen (Aleve) have not been done. Even so, Dr. Diker Cohen says it may be wise to limit them because they can irritate the gastrointestinal tract and worsen GLP-1 side effects like nausea or heartburn.

The bottom line: if you take a GLP-1 or are preparing to start one, talk with your doctor about any other medications you use. In most cases, the interaction may not be a major problem, but it is worth checking to be safe.