Are Semaglutide Injections Safe? What the Evidence Actually Shows

The side effects most people actually experience

A question our prescribers hear most weeks goes something like this: "I've read the side-effect list and it's terrifying — is this actually typical?" The honest answer is that the most common effects are gastrointestinal, and most people find they are manageable rather than severe. According to the NHS semaglutide medicines page, nausea tops the list, followed by constipation, diarrhoea, vomiting, indigestion and fatigue. These tend to surface when treatment starts or after a dose increase, and they typically ease within one to two weeks as the body settles.

What helps? Eating smaller portions, keeping meals lower in fat, staying well hydrated, and not eating too close to the injection are practical steps worth knowing about. Your prescriber and the Patient Information Leaflet are the right places for guidance specific to your situation. The broader picture, including how the medicine works and what the injection process involves, is covered in our overview of semaglutide injections.

Less common effects include headache, dizziness, injection-site reactions and burping. These are real, documented, and worth knowing about, but they affect a minority of users and rarely require stopping treatment. The key is not to be surprised by them, which is exactly why the clinical conversation before you start matters so much.

The risks that need a prescriber's eye

Some risks are infrequent but serious enough that the regulator has specifically flagged them. In January 2026, the MHRA published a Drug Safety Update on GLP-1 medicines that highlighted acute pancreatitis as a known, albeit uncommon, risk. The symptom to recognise is severe stomach pain that comes on suddenly, may spread to the back, and doesn't settle on its own, with or without vomiting. That warrants same-day medical attention, not a wait-and-see approach.

Gallbladder problems are also documented: gallstones and inflammation can develop, particularly with rapid weight loss. Symptoms include upper-right abdominal pain, nausea and fever. Dehydration becomes a concern if vomiting or diarrhoea is severe enough to stop you drinking normally, in which case staying on the medicine and staying home is the wrong call.

For people with a personal or family history of medullary thyroid carcinoma or a condition called MEN2, semaglutide is contraindicated. A history of pancreatitis and certain gastrointestinal conditions also require careful prescriber review. This is the kind of detail that gets explored properly in a consultation, not by ticking boxes on a website. If you want to understand how the injection itself is administered, our guide to taking semaglutide injections covers technique, storage and timing.

When to seek medical help, and when not to delay

Most people on semaglutide will not have an emergency. But there are symptoms that should prompt a call to 111 or a visit to A&E rather than waiting for a routine appointment. Seek urgent help if you experience: severe and persistent stomach or back pain (possible pancreatitis), signs of a serious allergic reaction such as swelling of the face, lips or throat, sudden or worsening changes to your vision, or symptoms of severe dehydration, dark urine, dizziness when standing, very little urine output.

Contact your GP or prescriber if you notice low mood or any thoughts of self-harm, as mood changes have been reported with GLP-1 medicines, though causality is still being studied. Side effects that feel unmanageable, even if not dangerous, are also worth raising rather than pushing through alone. Our detailed look at semaglutide's safety specifically in a weight-loss context covers additional nuance around contraindications and monitoring.

Any suspected side effect can also be reported to the MHRA via the Yellow Card scheme, the link is in the safety facts above. It takes only a few minutes and directly feeds into the post-market surveillance that keeps medicines safer over time.

Who should not use semaglutide injections

The licensed use of semaglutide for weight management in the UK (sold as Wegovy) covers adults with a BMI of 30 or above, or 27 and above alongside a weight-related health condition. But a qualifying BMI alone doesn't mean the medicine is automatically appropriate. Semaglutide is not recommended during pregnancy, while breastfeeding, or in the period before trying to conceive. It is not licensed for anyone under 18.

People with certain thyroid conditions, a past episode of pancreatitis, or specific bowel conditions need a careful clinical conversation about whether the benefits outweigh the risks in their individual case. Oral contraceptive users should also know that GLP-1 medicines more broadly can affect how some medicines are absorbed during the early phase of treatment, this is worth discussing with your prescriber.

At nume, the clinical team (you can read about our approach on the clinical team page) reviews every consultation personally before any prescription is issued. Side effects, contraindications and your current medicines are part of every assessment. If you'd like to understand what that process looks like end to end, the semaglutide injections overview is a good place to start, or you can go straight to check your eligibility with our prescribers.