What drugs can you not take with Wegovy, and why does it matter?

What the official prescribing guidance says about Wegovy and other medicines

The Summary of Product Characteristics for Wegovy, published on the eMC, notes that semaglutide has a low potential for pharmacokinetic drug interactions, meaning it does not significantly affect the enzymes that break down most medicines in the liver. That is the reassuring part. The less straightforward part is gastric emptying. By slowing the rate at which the stomach empties, semaglutide can change how quickly co-administered oral medicines enter the bloodstream, altering their absorption profiles without changing how the liver later processes them.

The NHS patient information for semaglutide lists this as the primary interaction mechanism to be aware of. In clinical studies, semaglutide's effect on the absorption of other oral drugs was modest overall, but even a modest shift matters for narrow-therapeutic-index medicines, those where a small change in blood level separates a dose that works from one that does not. If you take any medicine of that type, your prescriber will want to know. A clinician review before every dispensing is standard at a properly regulated pharmacy, which is exactly why that step exists.

For a fuller look at the broader semaglutide interaction picture, the full list of what not to take with Wegovy covers both drug classes and specific substances in more detail.

The interactions that come up most often in practice

A question our prescribers hear most weeks is whether a patient's existing medicines will cause a problem with Wegovy. In the majority of cases they will not, but there are a handful of drug categories where the conversation matters.

Insulin and sulfonylureas. For people with type 2 diabetes using Wegovy alongside insulin or a sulfonylurea (glibenclamide, gliclazide, glipizide and similar), the combination lowers blood glucose more powerfully than either alone. The result is a meaningfully higher risk of hypoglycaemia. Clinical guidelines typically recommend reducing the insulin or sulfonylurea dose before starting semaglutide, not after the first episode of low blood sugar. Your prescriber handles this adjustment; it is not something to manage unilaterally.

Oral contraceptive pills. NHS guidance advises discussing your contraception with your prescriber before starting Wegovy. Delayed gastric emptying can reduce the rate of pill absorption, particularly with combined pills. While semaglutide's specific effect on oral contraceptive bioavailability was studied and found to be modest, the precaution stands, a non-oral method (patch, implant, injection or coil) may be suggested for reliability. This is a notably different picture from tirzepatide, where the four-week precaution after each dose increase is more explicit in product guidance. Our semaglutide overview explains the background in fuller context.

Narrow-therapeutic-index oral medicines. Medicines such as warfarin, certain anti-epileptics and some immunosuppressants need stable, predictable absorption to maintain safe blood levels. Wegovy's gastric-emptying effect is not dramatic, but if you are on one of these medicines, your prescriber or GP may want closer monitoring when you start semaglutide, particularly in the dose-escalation phase.

Other GLP-1 or weight-loss medicines. Wegovy should not be combined with other GLP-1 receptor agonists (such as Ozempic, which contains the same active ingredient) or with other injectable semaglutide products. If you are unsure which drugs are semaglutide and therefore overlap with Wegovy, that page sets out the full picture clearly. If you are considering switching or adding treatment, the right route is through your prescriber, not adjusting doses yourself. The drug interaction detail page covers the GLP-1 overlap question specifically.

Medicines, supplements and substances that deserve mention even if they seem minor

Prescription medicines are not the only consideration. Several over-the-counter products and supplements can complicate semaglutide treatment in ways that often go unmentioned.

Oral thyroid medicines (levothyroxine). Levothyroxine is famously sensitive to timing and co-administration. It is already taken first thing in the morning on an empty stomach with water, for exactly the absorption reasons that also apply to Wegovy. If you take levothyroxine, tell your prescriber, they will guide you on spacing. The full medications guide for semaglutide addresses this in detail.

Alcohol. Not a drug interaction in the pharmacokinetic sense, but alcohol amplifies hypoglycaemia risk in people using Wegovy alongside diabetes medicines, and the nausea Wegovy can cause in the early weeks combines poorly with alcohol for most people. Worth flagging at consultation.

Iron and calcium supplements. These can interfere with the absorption of other medicines generally; timing matters. On Wegovy, altered gastric emptying is an additional variable. Your pharmacist can advise on spacing if you take either regularly.

Herbal supplements. St John's Wort is a CYP enzyme inducer that affects numerous medicines. If you take it alongside anything with a narrow margin of safety, that needs to be on your prescriber's radar regardless of Wegovy.

The safest habit is straightforward: bring a list of everything (prescribed, bought over the counter, or taken as a supplement) to your consultation, and if you want a detailed breakdown of what you cannot take with semaglutide, that guide covers the key categories in one place. For verified information on semaglutide's interaction profile, the NHS semaglutide page and the MHRA Yellow Card scheme are both worth bookmarking, Yellow Card lets you report any unexpected effect you notice on treatment.

If you are already on Wegovy and a new medicine is being added, the prescriber writing the new prescription also needs to know you are on semaglutide. That conversation sometimes gets missed, especially if it is a walk-in or urgent appointment. It matters.

For anyone still working out whether Wegovy is the right treatment given their current medicines, our free consultation gives you direct access to a GPhC-registered prescriber who reviews each case individually. It costs nothing to ask.