The overall picture: mostly gut-related, mostly mild

Semaglutide mimics a gut hormone, so it is no surprise the side effects people notice most are digestive. In OASIS 4 — the phase 3b trial that supported the tablet's approval — gastrointestinal adverse events affected about 74% of people taking oral semaglutide 25 mg, compared with about 42% on placebo, and were described as mostly mild to moderate and transient.[2][4]

The high figure sounds alarming until you look at what people did with it. In the same trial, the share who stopped treatment because of side effects was small and barely above placebo — about 7% on oral semaglutide against about 6% on placebo.[7] Gut symptoms were common but, for most, tolerable enough to keep going, and Novo Nordisk describes the tablet's overall safety profile as comparable to earlier semaglutide weight-management trials,[1] with the UK SmPC calling it consistent with the injection's trials.[4]

Key takeaway

Common does not mean severe. Gut side effects are frequent with the Wegovy pill, but in the trial they were mostly mild, mostly temporary, and rarely a reason to stop — only about 1 in 14 people discontinued because of side effects, similar to placebo.[4][7]

The most common side effects

The Wegovy pill's common side effects are the familiar semaglutide profile. According to the UK patient leaflet, the most commonly reported include:[5]

  • Nausea — the classic GLP-1 side effect
  • Diarrhoea and constipation — the gut can react in either direction
  • Vomiting
  • Abdominal (stomach) pain
  • Indigestion or heartburn (an upset stomach)
  • Bloating and belching
  • Headache, tiredness or fatigue, and dizziness
  • Low blood sugar (hypoglycaemia) — common in people with diabetes, but uncommon (up to 1 in 100) in people without

The UK Summary of Product Characteristics (SmPC) gives the same gut-dominated picture and notes that these effects were reported most often while the dose was being increased.[4]

How often: the figures for the tablet

The UK product information gives per-symptom figures for the 25 mg pill from OASIS 4, over 64 weeks: nausea affected 46.6% of people on the tablet (18.6% on placebo), vomiting 30.9% (5.9%), constipation 20.1% (9.8%) and diarrhoea 17.6% (8.8%). Hair loss was reported by 6.4% (2.0% on placebo), and a change in skin sensation, such as tingling or sensitive skin, by 4.9% (none on placebo).[4] These are trial figures, not a prediction for any one person; a prescriber or pharmacist can talk you through what they mean for you.

Why side effects peak during dose escalation

No one new to semaglutide starts on the full 25 mg dose — the one reported exception is people already established on the 2.4 mg once-weekly Wegovy injection, who can be transitioned directly to the 25 mg once-daily tablet by their prescriber.[3] For everyone else, the UK dose ladder climbs in steps — 1.5 mg, then 4 mg, 9 mg and 25 mg, with a minimum of one month at each level before moving up.[3] That slow climb exists for exactly this reason: the US label says the schedule is there to reduce the risk of gastrointestinal side effects,[7] and the UK SmPC notes these were reported most often during dose escalation.[4]

Practically, that means the toughest stretch for most people is the escalation phase itself rather than the time spent settled on a stable dose.[4] If side effects are hard to manage, the pace is set by the prescriber, who can hold a dose for longer or step back down. Our Wegovy pill dosage page sets out the full titration ladder and how the increases are decided.

Serious risks to know about

Beyond the gut symptoms, semaglutide has less common but more serious risks. The UK SmPC and patient leaflet for the tablet flag the following to watch for and report.[4][5]

When to seek urgent help

Severe, persistent stomach pain can be a sign of acute pancreatitis (inflammation of the pancreas): the UK patient leaflet says to stop the medicine and seek urgent medical help.[5] Do not wait for a routine appointment if this happens.

Pancreatitis

Acute pancreatitis is a warning for semaglutide medicines, and the UK leaflet rates it uncommon (up to 1 in 100 people). The warning sign is severe, persistent abdominal pain, sometimes felt in the back, and the advice is to seek urgent medical help if it occurs.[5]

Gallbladder problems

Gallstones are a common side effect: in OASIS 4 they were reported in 2.5% of people on the tablet and 1% on placebo.[4] The UK leaflet also lists raised bilirubin, which can cause jaundice (yellowing of the skin or the whites of the eyes), as uncommon.[5]

Dehydration and kidney function

Because vomiting and diarrhoea can cause fluid loss, the resulting dehydration can, in rare cases, worsen kidney function.[4] The UK leaflet's advice is simple: drink enough fluids to prevent dehydration, especially if you have kidney problems.[5]

Low blood sugar (hypoglycaemia)

The risk of hypoglycaemia is increased when semaglutide is combined with insulin or a sulphonylurea (a type of diabetes tablet), according to the UK SmPC.[4] The leaflet lists low blood sugar as common in people with diabetes and uncommon in people without.[5] This is one of the reasons a prescriber needs a full picture of your other medicines before starting.

Diabetic eye disease (retinopathy)

In people with diabetes, a rapid improvement in blood glucose can transiently worsen diabetic retinopathy, the UK product information says.[4] Anyone with existing eye disease should make sure their prescriber knows.

Heart rate

A small increase in resting heart rate has been observed with semaglutide: in OASIS 4 the average rise on the tablet was 2 beats per minute, according to the UK SmPC.[4]

Mood changes

Mood changes are not listed as a side effect in the UK patient leaflet or SmPC for the tablet.[4][5] Even so, if you notice a change in mood, raise it with your prescriber rather than pushing through.

The thyroid class warning

In the United States, semaglutide carries a boxed warning about a risk of thyroid C-cell tumours, including medullary thyroid carcinoma. It is a class warning based on studies in rodents, and it is why the US label rules out use in people with certain thyroid or endocrine conditions.[7] The UK SmPC describes the rodent tumours as a class effect of GLP-1 medicines whose relevance to humans is considered low but cannot be completely excluded.[4]

In practice this means being alert to the symptoms the US label asks people to report — such as a lump in the neck or hoarseness — while remembering the evidence for a human risk comes from animal data.[7] If you have a personal or family history of thyroid cancer, this is a conversation to have with a prescriber before anything else.

Who should not take it: contraindications

A contraindication means the medicine should not be used at all. For the Wegovy pill, the UK SmPC lists one contraindication:[4]

  • Allergy (hypersensitivity) to semaglutide or to any of the tablet's other ingredients

The US label also rules out use in people with a personal or family history of medullary thyroid carcinoma (MTC) or with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2) — a rare inherited condition that raises the risk of certain tumours.[7] These are not contraindications in the UK product information, but if either applies to you, tell your prescriber.

Pregnancy. The tablet should not be used in pregnancy or while breastfeeding. Because semaglutide has a long half-life — meaning it takes a while to clear from the body — the UK SmPC says treatment should be stopped at least two months before a planned pregnancy.[4] If you could become pregnant, this is another point to settle with a prescriber before starting.

Key takeaway

The Wegovy pill is a prescription-only medicine for a reason: the common side effects are manageable for most people, but the serious risks and contraindications need a prescriber who knows your full history and other medicines. It is one option a prescriber may discuss, never something to start on your own. How its side-effect profile compares with the injection is covered on our pill vs injection page.

Reporting a side effect: the Yellow Card scheme

If you take any medicine and have a side effect, you are encouraged to report it. The MHRA Yellow Card scheme collects reports of suspected side effects, which helps the regulator monitor the safety of medicines in real-world use.[6] You do not need to be certain the medicine caused the problem to report it.

Reporting is not a substitute for medical care. For anything severe or sudden — persistent stomach pain, signs of an allergic reaction, or symptoms that worry you — seek urgent help first, and speak to your GP or pharmacist about any side effect that does not settle.

Frequently asked questions

What are the most common side effects of the Wegovy pill?

They are mostly gut-related: nausea, diarrhoea, vomiting, constipation and stomach pain, plus headache, tiredness, indigestion, dizziness, bloating, belching and, in people with diabetes, low blood sugar.[5] In OASIS 4, gastrointestinal side effects affected about 74% of people on oral semaglutide 25 mg versus about 42% on placebo, and were mostly mild to moderate.[2][4]

Do the side effects get better over time?

For most people the gut side effects are described as mild to moderate and transient,[4] and the UK SmPC says they were reported most often while the dose was being increased.[4] The dose is stepped up slowly — 1.5 mg, then 4 mg, 9 mg and 25 mg, with at least a month at each step[3] — which the US label says is designed to reduce them.[7] Whether to slow down, hold or stop is a decision for the prescriber.

What are the serious risks of the Wegovy pill?

Semaglutide carries a boxed warning in the US about a risk of thyroid C-cell tumours, based on animal studies.[7] Other risks in the UK product information include acute pancreatitis, gallstones, dehydration that can rarely worsen kidney function, low blood sugar when combined with insulin or sulphonylureas, a possible temporary worsening of diabetic eye disease, and a small rise in resting heart rate.[4] Seek urgent help for severe, persistent stomach pain.

Who should not take the Wegovy pill?

In the UK, the only contraindication listed is allergy to semaglutide or any of the tablet's other ingredients;[4] the US label also rules out use with a personal or family history of medullary thyroid carcinoma (MTC) or with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).[7] It should not be used in pregnancy, and the UK SmPC says to stop at least two months before a planned pregnancy.[4] Suitability is always assessed by a prescriber.

How do I report a side effect?

Report suspected side effects through the MHRA Yellow Card scheme and speak to your GP or pharmacist.[6] Reporting helps the regulator monitor the safety of medicines. For severe or sudden symptoms, seek urgent medical care rather than waiting.

Further reading

References

  1. Novo Nordisk. FDA approval of the Wegovy pill (oral semaglutide 25 mg) — company announcement, 22 December 2025: source for the tablet containing semaglutide (the same active ingredient as the Wegovy injection), the 25 mg once-daily maintenance dose and the safety profile described as comparable to previous semaglutide weight-management trials. novonordisk.com
  2. Wharton S, Lingvay I, Bogdanski P, et al. "Oral Semaglutide at a Dose of 25 mg in Adults with Overweight or Obesity" (OASIS 4). New England Journal of Medicine, 18 September 2025;393:1077–1087 — gastrointestinal adverse events (74.0% vs 42.2% with placebo). doi.org/10.1056/NEJMoa2500969 Trial registration: ClinicalTrials.gov NCT05564117. clinicaltrials.gov
  3. Medicines and Healthcare products Regulatory Agency (MHRA). "First GLP-1 tablet for weight loss approved in the UK" — press release, 11 June 2026: UK dose ladder (1.5 mg → 4 mg → 9 mg → 25 mg, minimum one month at each dose) and the note that patients on the 2.4 mg once-weekly semaglutide injection can be transitioned straight to the 25 mg once-daily tablet. gov.uk
  4. Novo Nordisk. Wegovy 25 mg tablets — UK Summary of Product Characteristics (text revised 06/2026): section 4.3 (hypersensitivity is the only contraindication); section 4.4 (dehydration and kidney function, acute pancreatitis, hypoglycaemia with insulin or a sulfonylurea, diabetic retinopathy); section 4.6 (not for use in pregnancy or breast-feeding; stop at least 2 months before a planned pregnancy); section 4.8 (safety profile consistent with the semaglutide injection trials; OASIS 4 figures for nausea, vomiting, constipation, diarrhoea, hair loss, altered skin sensation, gallstones and heart rate; gut effects most frequent during dose escalation, mostly mild to moderate and of short duration; mood changes not listed); and section 5.3 (rodent thyroid C-cell tumours). medicines.org.uk
  5. Novo Nordisk. Wegovy tablets — UK patient information leaflet (revised 06/2026): the side-effect list and frequency bands, including low blood sugar (common in people with diabetes, uncommon without), acute pancreatitis (uncommon; stop and seek urgent help), raised bilirubin with jaundice (uncommon) and drinking enough fluids; mood changes are not among the listed side effects. medicines.org.uk
  6. MHRA. Yellow Card scheme — report a suspected side effect. yellowcard.mhra.gov.uk
  7. US Food and Drug Administration. Wegovy (semaglutide) injection and tablets — US Prescribing Information, revised 06/2026 (via DailyMed): boxed warning on thyroid C-cell tumours; contraindications, including a personal or family history of MTC or MEN 2; tablet dose escalation to reduce the risk of gastrointestinal side effects; thyroid symptoms to report, such as a lump in the neck or hoarseness; and 6.9% vs 5.9% of patients stopping the 25 mg tablet because of adverse reactions. dailymed.nlm.nih.gov