Short answer: They can. All four US labels say these medicines slow stomach emptying, which can change how pills taken by mouth are absorbed. Semaglutide 1 mg did not change absorption of the medicines tested to a meaningful degree, but the semaglutide tablet raised levothyroxine exposure by 33%. The Mounjaro and Zepbound labels ask for closer monitoring of drugs like warfarin and advise backup birth control for 4 weeks after starting and after each dose increase.
GLP-1 medicines slow the rate at which the stomach empties. The Ozempic label says semaglutide delays early stomach emptying after a meal. The Mounjaro and Zepbound labels say tirzepatide delays stomach emptying, with the largest effect after the first dose and less after later doses.
Because a pill has to leave the stomach before it is absorbed, each label has a section called "Oral Medications" saying this delay has the potential to affect how other medicines taken by mouth are absorbed.
The Ozempic label reports interaction studies at the 1 mg dose with metformin, an oral contraceptive (ethinyl estradiol with levonorgestrel), warfarin, digoxin and atorvastatin. Semaglutide did not affect their absorption to any clinically relevant degree, and the label says no dose adjustment is needed for them. It still says caution should be used with oral medicines.
The Wegovy label adds a finding from the semaglutide tablet: levothyroxine (a thyroid hormone pill) exposure rose by 33% when taken together with oral semaglutide. The Wegovy label says to monitor the effects of oral medicines taken with Wegovy and to consider more clinical or lab monitoring for medicines with a narrow therapeutic index (where a small change in level matters) or that need monitoring anyway. For Wegovy tablets, it says to wait at least 30 minutes after the tablet before eating, drinking or taking other oral medicines.
The Mounjaro and Zepbound labels say to use caution with oral medicines and to monitor people taking oral medicines that depend on reaching a threshold level to work, or that have a narrow therapeutic index, naming warfarin as an example.
They also give specific advice on birth control pills. After a single 5 mg dose of tirzepatide, peak levels of the hormones in a combined pill fell by 55% to 66% and total exposure by 20% to 23%. The labels advise people using oral hormonal birth control to switch to a non-oral method, or add a barrier method, for 4 weeks after starting and for 4 weeks after each dose increase. Birth control that is not taken by mouth should not be affected. The tirzepatide and birth control article covers this in detail.
Tell every prescriber and your pharmacist which GLP-1 you take and your dose schedule. A full list of what you take, with dose times, makes timing questions like levothyroxine or a birth control pill easier to answer. Dose Track keeps every medicine and its schedule in one list, and the interaction checker flags known combinations.
Read more on Dose Track: Tirzepatide and the birth control pill · Metformin vs Ozempic · Interaction checker · Taking oral medications · Wegovy pill