What you cannot take with semaglutide — and why it matters

How semaglutide's effect on your stomach changes the picture for other medicines

The decision about what to take alongside semaglutide starts with understanding one mechanism: the medicine slows the rate at which your stomach empties. For most of the things you put in your mouth that is largely irrelevant. For medicines whose absorption depends on precise timing or a predictable transit through the gut, it can shift things meaningfully.

What that means in practice is that peak blood levels of some oral drugs may arrive later, be lower, or in some formulations higher than expected. No two medicines are affected identically. The semaglutide mixing page goes into specific categories in more detail; here the focus is on the groups that come up most often in clinical assessment.

The NHS semaglutide medicines page lists the main interactions to flag to a healthcare professional, and it is worth reading alongside the Patient Information Leaflet supplied with your treatment. Neither replaces a personal conversation with your prescriber, but they give you the language to have that conversation confidently.

Medicines that carry the greatest concern alongside semaglutide

The group that attracts the most clinical attention is blood-glucose-lowering drugs. If you take insulin, or a sulphonylurea such as glibenclamide or gliclazide, adding semaglutide significantly increases the risk of hypoglycaemia. Your prescriber will usually want to reduce the dose of the existing medicine before starting you on semaglutide, not leave both running at full strength. This is one reason why the consultation before any GLP-1 prescription carries real clinical weight.

Oral contraceptive pills sit in a separate category. Semaglutide does not chemically interact with the pill's hormones, but the slowed gastric transit can reduce absorption. Guidance on what not to take with Wegovy covers the practical steps your prescriber may suggest, typically adding a barrier method for a period after starting or after a dose increase, rather than stopping hormonal contraception altogether.

Medicines with a narrow therapeutic index (those where a small change in blood levels matters a great deal, such as warfarin or certain thyroid medications) warrant extra monitoring. Your prescriber and your GP should both know you are starting semaglutide so that any routine blood or INR checks can be scheduled appropriately. Think of it like telling your dentist about a new prescription before a procedure: a small piece of admin that removes a bigger risk.

What this means for your decision about starting treatment

If you are on several regular medicines, the interaction question can feel like a reason to hesitate. It is better understood as a reason to be thorough at the consultation stage rather than a barrier to treatment. Many people with complex medication lists do use semaglutide safely, because their prescriber has reviewed each drug and made adjustments where needed.

The full breakdown of medications to discuss with your prescriber is worth reading before your appointment. It covers categories including anticoagulants, antiepileptics and certain antibiotics that may be affected by the gastric-emptying change. The list of drugs that require discussion before starting Wegovy covers the branded semaglutide injection specifically.

Cost is a separate but connected question for many people at this stage. A single transparent price that includes the prescriber's review, the prescription and delivery means the medication-review conversation is already built in, with no extra consultation charge. Comparing Wegovy prices in the UK explains what different providers typically include and what they sometimes leave out.

Semaglutide is not recommended during pregnancy, while breastfeeding, or if you are trying to conceive, and it is not licensed for under-18s. If any of those apply to you, your prescriber will discuss the options. For everyone else, the starting point is a complete and honest list of your current medicines, bringing that list to your consultation is the single most useful thing you can do. You can explore what a full eligibility assessment looks like on the semaglutide eligibility page, or read about Wegovy as the licensed UK injectable form of semaglutide. Our clinical team reviews every consultation personally.

If you think semaglutide may be right for you and you want a prescriber to look at your medication list properly, check your eligibility with a free consultation.