Wegovy tablets: side effects, contraindications and when to see a doctor

The most common side effects of Wegovy tablets are digestive. In the OASIS 4 trial, 46.6% of people taking oral semaglutide had nausea (18.6% on placebo) and 30.9% had vomiting (5.9%). These effects mostly appear while the dose is being increased, and most were mild or moderate and short-lived. The Summary of Product Characteristics (SmPC) lists only one contraindication: allergy to any of its ingredients. However, it does not recommend the tablets during pregnancy or breastfeeding, for under-18s, or for people with severe kidney or liver impairment.

Wegovy tablets are oral semaglutide made by Novo Nordisk. They are authorised in Spain for weight management in adults and are available on prescription. This article covers what the SmPC and patient information leaflet on CIMA (the database of AEMPS, the Spanish medicines agency) say, along with the main clinical trial. Prices for each pack are covered in Wegovy tablets in Spain: price, prescription and how to get started.

What are the side effects of Wegovy tablets?

The SmPC groups adverse reactions by frequency, using data from the STEP 1-4 trials of the injectable version (2,650 adults over 68 weeks). In OASIS 4, where 204 adults took the tablet for 64 weeks, the side effects were similar. The one exception was dyspepsia, which moved into a higher frequency category.

• Very common (more than 1 in 10 people): nausea, vomiting, diarrhoea, constipation, dyspepsia or indigestion, abdominal pain, headache and fatigue.
• Common (up to 1 in 10): dizziness, taste disturbance, altered skin sensation (dysaesthesia), gastritis, gastro-oesophageal reflux, belching, flatulence, abdominal distension, gallstones (cholelithiasis) and hair loss. People with type 2 diabetes may also have hypoglycaemia and complications of diabetic retinopathy.
• Uncommon (up to 1 in 100): increased heart rate, low blood pressure, acute pancreatitis, delayed gastric emptying and raised amylase and lipase on blood tests.
• Rare and very rare: anaphylactic reaction and angioedema (rare), and non-arteritic anterior ischaemic optic neuropathy, or NAION (very rare). Intestinal obstruction is listed with an unknown frequency, based on reports received after the medicine went on the market.

How many people get nausea and other side effects? What OASIS 4 found

The rates of digestive side effects are high, and that is worth saying plainly. OASIS 4 was a double-blind trial in adults without diabetes who had obesity, or overweight with complications. Of those taking 25 mg oral semaglutide, 74.0% had some kind of gastrointestinal effect, compared with 42.2% on placebo. Looking at each effect, nausea affected 46.6%, vomiting 30.9% and constipation 20.1%. Dyspepsia, diarrhoea and abdominal pain each affected between 16.7% and 18.1%, roughly double the placebo rates.

Most of these episodes were mild or moderate and short-lived, with constipation lasting longest. Although almost half had nausea, only 3.4% stopped treatment permanently because of a digestive problem. Counting every reason, 18% stopped taking the tablet, compared with 25.5% on placebo. Serious adverse events, according to the results posted on ClinicalTrials.gov, occurred in 3.9% on oral semaglutide and 8.8% on placebo.

Outside the digestive system, OASIS 4 recorded hair loss in 6.4% (2.0% on placebo). It was always mild or moderate, was more common in people who lost 20% or more of their body weight, and had cleared up in about half of cases by the end of the trial. Gallstones occurred in 2.5% (1% on placebo), with no cases of cholecystitis. Altered skin sensation, such as burning or tingling, affected 4.9%, against none on placebo, and most people recovered without stopping treatment. Heart rate rose by an average of 2 beats per minute. Acute pancreatitis occurred in 0% on the tablet and 1.0% on placebo.

When do side effects appear, and why do they tend to ease off?

The SmPC is clear that digestive effects were seen mainly while the dose was being increased. Treatment doesn't start at the final dose. It begins at 1.5 mg a day and then goes up to 4, 9 and 25 mg, with at least four weeks at each step, so it takes at least 12 weeks to reach the maintenance dose. The SmPC also allows the dose to stay at the previous level if needed. Your doctor decides the pace.

The patient leaflet puts it simply: these effects are seen mainly while the dose is being increased and usually go away over time. Dizziness, if it happens, mostly occurs in the first four months. The fact that side effects tend to ease off doesn't mean you should put up with them in silence. Talk to your doctor about them. For practical tips on handling the digestive side effects of these treatments day to day, see Ozempic and Mounjaro side effects: what to expect and how to manage them.

Who shouldn't take Wegovy tablets?

The only formal contraindication in the SmPC is hypersensitivity to semaglutide or to either of its excipients, salcaprozate sodium and magnesium stearate. But there are quite a few situations where the SmPC doesn't recommend it or advises caution:

• Pregnancy: it should not be used. Treatment is stopped if you become pregnant or want to become pregnant. Because semaglutide has a long half-life, it should be stopped at least 2 months before a planned pregnancy.
• Breastfeeding: it should not be used. No semaglutide was found in breast milk, but salcaprozate sodium and some of its metabolites were, and a risk to the baby cannot be ruled out.
• Under-18s: there are no data for the tablets (the pen is approved from age 12).
• Severe renal impairment (eGFR below 30 ml/min/1.73 m²) and severe hepatic impairment: not recommended. No dose adjustment is needed for mild or moderate impairment, although caution is advised for liver impairment. People with moderate renal impairment may have more digestive side effects.
• Type 1 diabetes, class IV heart failure, use of other weight-loss products, severe gastroparesis, and uncontrolled or unstable diabetic retinopathy: not recommended.
• Another GLP-1 receptor agonist at the same time: the two should not be combined.
• Use with caution, because experience is limited: people aged 85 or over, people with mild or moderate hepatic impairment, and people with inflammatory bowel disease.

Who can be prescribed it, based on BMI, is explained in BMI requirements and steps to get a prescription for oral Wegovy. Your doctor also needs to know about everything you take, because the SmPC describes interactions that need monitoring, such as with levothyroxine or warfarin.

What precautions does the SmPC list?

Anaesthesia and sedation. Cases of pulmonary aspiration have been reported in people on GLP-1 agonists who had a general anaesthetic or deep sedation. This happens because the stomach empties more slowly and may still contain food. If you are due to have an operation or a procedure under general anaesthetic or deep sedation, the patient leaflet asks you to tell the doctor that you take Wegovy.

Dehydration and the kidneys. Nausea, vomiting and diarrhoea can lead to dehydration and, in rare cases, worsening kidney function. The SmPC advises taking steps to avoid fluid loss, with extra care if your kidneys already don't work as well as they should.

Pancreatitis. It is uncommon, but the SmPC asks patients to know the symptoms. If pancreatitis is suspected, treatment is stopped, and if it is confirmed, treatment is not restarted. Extra caution is needed if you have had pancreatitis before. In the STEP programme for the injectable version, it occurred in 0.2% of people, compared with less than 0.1% on placebo.

Eyesight. Epidemiological studies link semaglutide with a higher risk of NAION, damage to the optic nerve that can cause painless loss of vision in one eye. In adults with type 2 diabetes, the relative risk is roughly double, which works out at about one extra case per 10,000 person-years. AEMPS issued a safety notice about this in 2025. Sudden loss of vision needs an eye examination.

When should you see a doctor?

The patient leaflet separates what can wait until your next appointment from what can't. It says to get medical help without delay if you have:

• Severe, persistent stomach pain, which may spread to your back. This could be pancreatitis.
• Difficulty breathing, rapid swelling of the face, throat, arms or legs, light-headedness, a fast heartbeat or loss of consciousness. These could be signs of a severe allergic reaction.
• Sudden loss of vision or vision that gets worse quickly.
• Severe constipation with stomach pain, bloating or vomiting, which the leaflet describes as a possible intestinal obstruction.
• A pregnancy during treatment, or having taken more tablets than prescribed.

You should also check in with your doctor, not as an emergency but without letting it slide, if nausea, vomiting or diarrhoea make it hard to stay hydrated (especially if you have kidney problems), if you have diabetes and notice changes in your vision, or if digestive symptoms don't settle over the weeks. You can report any suspected side effect to your doctor or pharmacist, even if it isn't listed in the leaflet.

Key points to remember

Digestive side effects are common with Wegovy tablets, especially while the dose is going up, and most are mild and temporary. The warning signs are few and specific, and they are worth knowing. Whether the treatment is right for you is a decision for a doctor who has reviewed your medical history.

What is available in Spain today for medically supported weight loss is a medical weight-loss treatment. It includes an initial assessment, a prescription from a registered doctor where appropriate, and ongoing follow-up with someone who checks in with you on how you're getting on. You can:

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