Wegovy Drug Interactions You Should Know About

You've just opened your medicines cabinet and felt a flicker of doubt

That's a very reasonable reaction. Picking up a new prescription-only medicine while you're already on daily tablets (or even a weekly pill) raises a fair question: will they work against each other? The honest answer is that semaglutide has relatively few interactions that require stopping a medicine altogether, but it does have one mechanism that quietly affects a wider range of drugs than most people expect.

Semaglutide is a GLP-1 receptor agonist. One of its consistent effects is slowing gastric emptying: food, and anything you swallow alongside it, moves more slowly from your stomach into the small intestine, where absorption happens. For most medicines this is a modest change and clinically unimportant. For a small number of drugs, where the blood level needs to stay within a tight range, even a modest shift in absorption rate can change how well the medicine works, or increase the risk of it doing too much. The semaglutide overview on our site covers the broader clinical background if you want it.

NHS guidance on weight-management injections flags this mechanism specifically, and the Mounjaro and Wegovy patient information leaflets both carry interaction warnings. The right move is not to panic, but to tell every clinician who prescribes for you that you are starting or already on Wegovy.

The medicines that need the closest attention on Wegovy

Warfarin sits at the top of most clinicians' watchlists. It has a narrow therapeutic window: the difference between a dose that prevents clots and one that causes bleeding is small. If semaglutide slows its absorption or alters gut motility in a way that changes how consistently warfarin reaches its target level, your INR can drift. Anyone anticoagulated with warfarin should have INR checked more frequently when starting Wegovy or changing dose, and your prescriber should know before you begin.

Levothyroxine (the most commonly prescribed thyroid replacement in the UK) is absorbed best on an empty stomach, and its absorption is sensitive to timing. Because semaglutide changes the gut environment, thyroid function tests should be watched for the first few months on treatment. The same principle applies to other medicines where the standard advice is already to take them at a specific time relative to food.

Oral contraceptive pills deserve a separate mention. The concern here is not that semaglutide makes the pill ineffective outright, but that slower gastric emptying can reduce peak absorption of oral hormones. NHS clinical guidance advises adding a barrier method (condoms) for the first four weeks of starting Wegovy and for four weeks after any dose increase. This is precautionary but consistently recommended. If you would like a full breakdown of how this applies in practice, our page on interactions with Wegovy covers contraception in more detail.

You can read the NHS's patient guidance on semaglutide, including its interaction section, directly on the NHS semaglutide medicines page.

Over-the-counter medicines and supplements: the ones people forget to mention

The interactions that catch people out most often are not the prescription items, those are usually on a hospital letter or a repeat prescription list. It's the things bought at a supermarket or health shop that go unmentioned: ibuprofen, aspirin, iron tablets, St John's Wort, high-dose vitamins. Each can carry its own consideration on Wegovy.

Aspirin is worth a specific note. Low-dose aspirin (75mg daily) is commonly prescribed for cardiovascular protection and is generally continued alongside Wegovy, but the combination should be disclosed to your prescriber because both aspirin and GLP-1 medicines can each affect the gut. Our page on semaglutide and aspirin interactions goes into the detail on that specific pairing. St John's Wort, available over the counter, is a known inducer of liver enzymes and interacts with a surprisingly long list of medicines, it should be disclosed like any other drug.

Supplements matter too. High-dose omega-3, for example, can affect platelet function. Iron and calcium preparations can bind to and reduce absorption of other oral medicines if taken at the same time. None of this means you need to stop taking them, but your prescriber can only help you manage these things if they know about them.

A practical approach: before your Wegovy consultation, write down every tablet, capsule, liquid or supplement you take, including the ones you buy yourself. That list is one of the most useful things you can bring. You can explore more detail on semaglutide drug interactions, including guidance on the semaglutide ampule format used in some preparations, on our dedicated semaglutide interactions page.

What happens at your nume consultation (and what to do if your medicine list changes later

At nume, every consultation is read by a GPhC-registered Independent Prescriber) a real clinician, not automated software, before any prescription is issued. Reviewing your current medicines is part of that process, not a box-ticking exercise. If something in your medicines list needs a closer look, you'll hear about it the same day.

Drug interactions with semaglutide don't only matter at the start. If your GP adds a new medicine partway through treatment (or you start taking something regularly over the counter) it's worth flagging it with your prescriber. Dose increases of Wegovy can also briefly re-intensify the gastric-emptying effect, which is one reason our clinical team reviews your situation before every repeat, not just at the beginning. If questions come up between orders, our aftercare team is available seven days a week.

If you're still working out which treatment might be right for you, the free consultation page is the place to start, and it's the point at which your full medicines list goes in front of a prescriber. There's no commitment to proceed, and our FAQs cover many of the practical questions people have before they begin.

For a broader look at Wegovy (how it works, what it's licensed for, and what the trial evidence shows) the Wegovy treatment overview on our site is a good starting point.