Oral semaglutide tablets are currently under review by the Medicines and Healthcare products Regulatory Agency (MHRA), with a UK licensing decision expected in late 2026. While the tablet is not yet available in the UK, injectable Wegovy and Mounjaro are currently licensed and available for weight management in adults who meet the prescribing criteria.
The oral tablet and the injectable pen share the same active ingredient, but they're not identical in how they affect the body, and their side effect profiles reflect that. The tablet's strict fasting requirement, daily dosing schedule, and different absorption mechanism produce a distinct tolerability pattern that is worth understanding separately. This guide focuses specifically on the oral formulation, drawing on data from the OASIS 4 phase 3 trial to explain what side effects oral semaglutide causes, how frequently they occur, and what can be done to reduce their impact.
Why Oral Semaglutide Causes Side Effects
Semaglutide is a GLP-1 receptor agonist, meaning it mimics the action of a naturally occurring hormone called glucagon-like peptide-1. This hormone is released by the gut after eating and plays a key role in regulating appetite, slowing the movement of food through the stomach (a process called gastric emptying), and signalling fullness to the brain.
These mechanisms are what make semaglutide effective for weight management, but they're also the primary reason behind its most commonly reported side effects. When food moves more slowly through the digestive system than usual, nausea, bloating, and changes in bowel habits are a predictable consequence. This isn't a sign that something has gone wrong; it reflects the drug working as intended.
The oral tablet formulation requires a specific absorption process: it must be taken on an empty stomach with no more than 120ml of plain water, and nothing else can be consumed for at least 30 minutes afterwards. This strict fasting requirement helps the tablet be absorbed effectively but can itself contribute to digestive discomfort, particularly in the early weeks of treatment.
How Do the Side Effects of Oral Semaglutide Differ From the Injection?
The injectable and oral forms of semaglutide share the same active ingredient, but their tolerability profiles are not identical. The most clinically meaningful difference is the overall rate of gastrointestinal side effects: in OASIS 4, 74% of participants on the oral tablet reported GI adverse events of any kind, compared with around 65% in the STEP 1 trial of the injectable form.1 The difference is modest but real, and is likely explained by two factors.
First, the oral tablet's absorption mechanism requires the stomach to be empty and contact with water to be minimal, which can itself heighten GI sensitivity. Second, the daily dosing of the tablet means the gut is exposed to semaglutide more consistently than with a weekly injection, which may reduce the brief tolerance window between doses that injectable users experience.
The types of side effects, however, are broadly the same: nausea, vomiting, diarrhoea, constipation, and abdominal discomfort dominate in both forms, and in both cases they tend to be most pronounced during dose escalation and improve over time. For a full guide to the side effects of injectable Wegovy, see our Wegovy injectable side effects article.
What Are the Most Common Side Effects of Oral Semaglutide?
The most frequently reported side effects of oral semaglutide are gastrointestinal in nature. Nausea was the single most common effect in the OASIS 4 trial,1 affecting 46.6% of participants on oral semaglutide compared with 18.6% on placebo, and the FDA prescribing information^2^ confirms this pattern across the full adverse reaction profile:
- Nausea - the single most common side effect, reported in 46.6% of participants taking oral semaglutide, compared with 18.6% in the placebo group
- Vomiting - reported in 30.9% of participants, compared with 5.9% on placebo
- Diarrhoea - one of the more frequently reported effects; rates for the oral formulation are expected to be similar to the injectable form, where it occurs in roughly one in four patients
- Constipation - reported in approximately 24% of patients taking injectable semaglutide in clinical trials; comparable rates are anticipated for the tablet
- Abdominal pain - including upper and lower stomach discomfort, reported in around 20% of patients on the injectable form
The prescribing information for the oral tablet notes that the types and frequencies of adverse reactions are similar to those seen with injectable semaglutide 2.4mg.
How Common Are Gastrointestinal Side Effects?
In OASIS 4, gastrointestinal adverse events of any kind were reported in 74% of participants taking oral semaglutide, compared with 42% in the placebo group.1 This is a notably higher rate than placebo, but the clinical picture is important: the majority of these events were mild to moderate in severity and resolved as the dose escalation period progressed.
Adverse events that led to discontinuing treatment were uncommon, occurring in 7% of the oral semaglutide group. Serious adverse events were less frequent in the semaglutide group than in the placebo group (3.9% versus 8.8%),3 which reflects the overall safety profile of the medicine.
Side effects are most likely to occur during the dose escalation phase, when the dose is being increased gradually over a 12-week period before reaching the maintenance dose. This is a deliberate feature of the prescribing schedule, giving the body time to adjust and reducing the risk of severe gastrointestinal symptoms.
How to Manage Nausea and Other Digestive Symptoms
Most gastrointestinal side effects are manageable with practical adjustments. The following steps are consistent with guidance from prescribing clinicians and pharmacists:
- Eat smaller, more frequent meals rather than two or three larger ones. Large meals sit in the stomach for longer when gastric emptying is slowed, which worsens nausea.
- Avoid high-fat and processed foods, particularly during the early weeks of treatment. Fat slows gastric emptying further and is a common trigger for nausea on semaglutide.
- Eat slowly and stop when you feel full. Semaglutide makes the fullness signal arrive earlier than usual; continuing to eat past that point significantly increases nausea risk.
- Stay well hydrated, especially if you are experiencing vomiting or diarrhoea. Dehydration can in rare cases affect kidney function when combined with significant gastrointestinal fluid loss.
- Avoid lying down immediately after eating. Staying upright for at least one to two hours after a meal reduces reflux and nausea.
- Take the tablet correctly. Oral semaglutide must be taken on an empty stomach with plain water only. Taking it with food or other liquids reduces absorption and is not consistent with the prescribing instructions.
Alcohol is worth approaching with caution during treatment. It can worsen nausea directly, and because semaglutide slows gastric emptying,4 alcohol is absorbed more slowly than usual, so its effects may feel delayed before hitting harder than expected. There's no absolute contraindication, but keeping alcohol intake low, particularly during the dose escalation phase, is sensible.
If symptoms are severe or are not settling after a few weeks, speak to your prescribing clinician. The dose escalation schedule can sometimes be paused at a lower dose to allow more time for adjustment, rather than discontinuing treatment.
Less Common Side Effects
Beyond the core gastrointestinal symptoms, semaglutide is associated with a number of other effects that occur less frequently:
- Headache and fatigue - reported in roughly one in ten patients, likely related to changes in calorie intake and blood sugar regulation in the early weeks
- Dizziness - can occur, particularly when standing up quickly; staying hydrated helps reduce this
- Increased heart rate - clinical trials with semaglutide have reported a mean increase of one to four beats per minute, with larger increases in a smaller proportion of patients
- Gallbladder-related symptoms - significant weight loss can increase the risk of gallstones; semaglutide trials have reported gallbladder events in a small proportion of patients, and any persistent pain in the upper right abdomen should be assessed promptly
These effects are generally manageable, but should be reported to your clinician if they are persistent or worsening. The FDA prescribing information for oral semaglutide^2^ notes that the overall adverse reaction profile is consistent with that of injectable semaglutide 2.4mg.
Serious but Rare Side Effects: What to Know
While the overall safety profile of semaglutide is well established, there are several rare but serious adverse effects that patients should be aware of.
Pancreatitis
In January 2026, the MHRA updated the product information for all GLP-1 receptor agonists, including semaglutide, to strengthen warnings about the risk of severe acute pancreatitis. This followed post-marketing data showing rare cases of necrotising and fatal pancreatitis. Between 2007 and October 2025, the MHRA received 1,296 Yellow Card reports of pancreatitis associated with GLP-1 receptor agonists^5^ across an estimated 25.4 million packs dispensed, representing a very small absolute risk.
Pancreatitis should be suspected if you experience severe, persistent abdominal pain that radiates to the back and may be accompanied by nausea or vomiting. This requires urgent medical attention. If pancreatitis is confirmed, semaglutide must be stopped and should not be restarted.
Vision Changes: NAION
In February 2026, the MHRA issued a Drug Safety Update confirming that non-arteritic anterior ischaemic optic neuropathy (NAION), a condition that can cause sudden, painless vision loss in one eye, has been very rarely reported in association with semaglutide.6 The MHRA's assessment found it to be a very rare side effect, with three spontaneous reports received via Yellow Card against an estimated 10.2 million packs of semaglutide dispensed in the UK up to August 2025.
Any sudden or rapidly worsening vision loss while taking semaglutide should be treated as urgent. Attend eye casualty or A&E immediately, and tell the clinical team you are taking semaglutide, as privately prescribed medications may not appear on your NHS record.
Thyroid Considerations
In rodent studies, semaglutide caused dose-dependent thyroid C-cell tumours. It's not currently known whether this finding translates to humans, but semaglutide is contraindicated in people with a personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia type 2 (MEN 2). Any unexplained lump in the neck or difficulty swallowing should be assessed by a doctor.
Do Oral Semaglutide Side Effects Go Away?
Yes, for most people. The gastrointestinal side effects of oral semaglutide are most pronounced during the dose escalation phase and typically decrease once the maintenance dose is established. In OASIS 4, gastrointestinal events were generally described as transient in nature,1 and discontinuation rates due to GI adverse events were low at 7%.
The structure of the escalation schedule, starting at a low dose and increasing every four weeks, is specifically designed to allow the body to adapt. For patients who do experience persistent or severe symptoms, clinicians have the option of pausing the escalation at a lower dose for a further period before continuing. This approach has been shown to improve tolerability without compromising the overall treatment outcome.
Constipation tends to persist longer than nausea and vomiting in some patients. Increasing dietary fibre and fluid intake is the standard first step for managing it. If constipation does not resolve, your clinician can advise on further options.
Nutritional Considerations During Treatment
Reducing calorie intake during semaglutide treatment can increase the risk of nutritional deficiencies, particularly if food choices are limited or appetite is significantly suppressed. Taking a daily multivitamin can help ensure baseline intake of key micronutrients during active weight loss, including vitamins A, C, D, and the B complex, which are often reduced when overall food intake falls.
This is particularly relevant for patients who are also taking Orlistat, which reduces the absorption of fat-soluble vitamins. If you are transitioning between treatments or taking any other weight management medication, speak to your pharmacist about whether additional nutritional support is appropriate.
When to Seek Medical Advice
Contact your GP or prescribing clinician if you experience:
- Severe or persistent nausea, vomiting, or diarrhoea that does not improve after several weeks
- Severe abdominal pain, especially if it radiates to the back, with or without nausea or vomiting
- Signs of dehydration: dizziness, rapid heartbeat, reduced urination, or extreme thirst
- Persistent constipation that does not respond to dietary adjustments
- Any unexplained lump in the neck, hoarseness, or difficulty swallowing
- Rapid or significant worsening of vision in one eye
Attend eye casualty or A&E immediately for sudden vision loss. For severe abdominal pain, seek urgent medical care and do not wait for a routine appointment.
Frequently Asked Questions
Do the side effects of Wegovy tablets go away?
Yes, for most people. The most common side effects of oral semaglutide, particularly nausea and vomiting, are most intense during the dose escalation phase and tend to ease once the maintenance dose is reached. In the OASIS 4 trial, gastrointestinal events were generally described as mild to moderate and transient. Constipation can persist longer than other GI symptoms in some patients, but dietary adjustments usually help. If side effects are severe or not settling after several weeks, speak to your prescribing clinician, as the escalation schedule can sometimes be paused at a lower dose to allow more time for adjustment.
What are the worst side effects of Wegovy tablets?
The most troublesome side effects reported by patients are nausea and vomiting, which affect roughly 47% and 31% of people respectively on the oral tablet. These are most severe during the early weeks of treatment when the dose is being increased. Serious but rare side effects include acute pancreatitis and, very rarely, sudden vision loss (NAION). The MHRA strengthened its warnings on both of these in early 2026. Severe, persistent abdominal pain radiating to the back or any sudden change in vision should be treated as urgent and require immediate medical attention.
When do Wegovy tablet side effects start?
Side effects typically begin within the first one to two weeks of starting treatment, as the body adjusts to the medication. They tend to peak when the dose is increased and then settle over the following weeks. Because the tablet uses a gradual 12-week dose escalation schedule starting from a low dose, the severity of early side effects is usually manageable. Patients who find a particular dose increase difficult can ask their clinician to pause escalation at that dose for longer before moving up.
How long do the side effects of Wegovy tablets last?
Nausea and vomiting usually improve significantly after the first few weeks on each new dose and often resolve or become minimal once the maintenance dose is established. Based on OASIS 4 trial data, gastrointestinal events were broadly transient. Constipation can take longer to settle and may persist throughout treatment for some patients. Any side effect that is worsening rather than improving, or that is still severe after several weeks, should be discussed with a clinician.
How can I reduce the side effects of Wegovy tablets?
The most effective steps are eating smaller, more frequent meals; avoiding high-fat and processed foods, especially in the early weeks; eating slowly and stopping when full; staying well hydrated; and not lying down immediately after eating. For the oral tablet specifically, it's also important to take it correctly: on an empty stomach with no more than 120ml of plain water, waiting at least 30 minutes before eating or drinking anything else. Alcohol can worsen nausea and should be kept to a minimum during the dose escalation phase. If symptoms are severe, your clinician can pause the dose escalation rather than stopping treatment entirely.
Do Wegovy tablets have fewer side effects than Mounjaro?
The side effect profiles of Wegovy (semaglutide) and Mounjaro (tirzepatide) are broadly similar, as both are GLP-1 receptor agonists that work by slowing gastric emptying. Both are associated mainly with gastrointestinal side effects: nausea, vomiting, diarrhoea, and constipation. There are no direct head-to-head trial data comparing their tolerability in equivalent doses. Some patients find one better tolerated than the other, but this varies individually. For a comparison of the two treatments, see our guide to Mounjaro vs Orlistat.
Is oral semaglutide available in the UK?
Not yet. The oral semaglutide tablet (Wegovy 25mg once daily) was approved by the US FDA in December 2025, but Novo Nordisk's application to the MHRA is still under review as of mid-2026, with a decision expected in late 2026. Once approved, private prescribing is likely to follow before NHS availability, which will also require a separate NICE health technology assessment. Injectable Wegovy (2.4mg and 7.2mg) and Mounjaro (tirzepatide) are both currently licensed and available in the UK.
Are semaglutide tablets the same as Ozempic?
No. Ozempic is an injectable semaglutide pen licensed for type 2 diabetes, and it's not licensed for weight management in the UK and should not be used as a substitute for Wegovy. The oral semaglutide tablet being developed for weight management is a distinct formulation at a higher dose (25mg daily), approved in the US as Wegovy in tablet form. Rybelsus is a separate oral semaglutide product (3mg, 7mg, and 14mg) licensed in the UK for type 2 diabetes only, not for weight loss.
References
- Wharton S, Lingvay I, Bogdanski P, et al. Oral semaglutide at a dose of 25 mg in adults with overweight or obesity. New England Journal of Medicine. 2025;393(11):1077-1087. doi:10.1056/NEJMoa2500969
- Novo Nordisk. Wegovy (semaglutide) tablets prescribing information. US Food and Drug Administration. Approved December 2025. accessdata.fda.gov
- Applied Clinical Trials Online. FDA Approves Oral Wegovy Following Positive Phase III OASIS 4 Trial Results. Published June 2026. appliedclinicaltrialsonline.com
- Novo Nordisk Ltd. Rybelsus 14 mg tablets Summary of Product Characteristics. Electronic Medicines Compendium (eMC). medicines.org.uk/emc
- Medicines and Healthcare products Regulatory Agency. GLP-1 receptor agonists: strengthened warnings for pancreatitis. Drug Safety Update. January 2026. gov.uk/mhra
- Medicines and Healthcare products Regulatory Agency. Semaglutide (Wegovy, Ozempic and Rybelsus): risk of Non-arteritic Anterior Ischemic Optic Neuropathy (NAION). Drug Safety Update. 5 February 2026. gov.uk/mhra
This article is intended for informational purposes only and does not replace professional medical advice. Always read the patient information leaflet supplied with your medication and speak to a healthcare professional if you have specific concerns.