The most common side effects of Ozempic are gastrointestinal, particularly nausea, diarrhoea, vomiting, abdominal pain and constipation. These effects are often most noticeable when treatment begins or the dose is increased and may improve as the body adjusts to semaglutide.
Ozempic can also cause less common but potentially serious problems. These include pancreatitis, gallbladder disease, dehydration and kidney problems, severe allergic reactions, worsening diabetic retinopathy in some patients, and hypoglycaemia when used with certain other diabetes medicines.
European regulators also recognise non-arteritic anterior ischaemic optic neuropathy (NAION), a condition that can cause sudden vision loss, as a very rare side effect of semaglutide.
This guide explains which Ozempic side effects are common, which symptoms require medical attention, and what current US and European product information says about important risks.
In brief
- The most common Ozempic side effects are nausea, vomiting, diarrhoea, abdominal pain and constipation.
- Gastrointestinal symptoms occur most often during dose escalation.
- Persistent vomiting or diarrhoea can cause dehydration and may contribute to kidney problems.
- Severe, persistent abdominal pain can be a warning sign of acute pancreatitis and requires medical assessment.
- Ozempic can increase the risk of hypoglycaemia when used with insulin or medicines that stimulate insulin release, such as sulfonylureas.
- People with diabetic retinopathy may require additional monitoring because rapid improvement in blood glucose can temporarily worsen retinopathy.
- Sudden loss of vision or rapidly worsening eyesight requires urgent medical attention. European regulators classify NAION as a very rare semaglutide side effect.
What are the most common side effects of Ozempic?
Ozempic contains semaglutide, a GLP-1 receptor agonist used to treat adults with type 2 diabetes. Like other medicines in this class, its most frequent adverse effects involve the digestive system.
In placebo-controlled US clinical trials, the five adverse reactions reported in at least 5% of patients treated with Ozempic were:
| Side effect | Ozempic 0.5 mg | Ozempic 1 mg | Placebo |
|---|---|---|---|
| Nausea | 15.8% | 20.3% | 6.1% |
| Vomiting | 5.0% | 9.2% | 2.3% |
| Diarrhoea | 8.5% | 8.8% | 1.9% |
| Abdominal pain | 7.3% | 5.7% | 4.6% |
| Constipation | 5.0% | 3.1% | 1.5% |
These percentages come from a pool of placebo-controlled trials and should not be interpreted as the probability that any individual patient will experience a particular symptom. Clinical-trial populations and real-world patients can differ.
Why does Ozempic cause nausea and stomach problems?
Semaglutide affects the gastrointestinal system as part of its pharmacological action. It can delay gastric emptying and also affects appetite and food intake.
In US placebo-controlled trials, gastrointestinal adverse reactions overall occurred in 32.7% of patients taking Ozempic 0.5 mg and 36.4% taking 1 mg, compared with 15.3% receiving placebo.
Most reports of nausea, vomiting and diarrhoea occurred while the Ozempic dose was being increased.
This is one reason Ozempic treatment begins at a low dose and is escalated gradually rather than starting immediately at a maintenance dose.
Do Ozempic side effects get better over time?
For many patients, gastrointestinal side effects are most noticeable when treatment starts or after a dose increase and become less troublesome over time. However, this is not true for everyone.
Symptoms that are severe, persistent or interfere with eating and drinking should not simply be assumed to be a normal part of treatment.
In the US placebo-controlled trials, 3.1% of patients receiving Ozempic 0.5 mg and 3.8% receiving 1 mg discontinued treatment because of gastrointestinal adverse reactions, compared with 0.4% receiving placebo.
Patients struggling with side effects should discuss them with the clinician managing their treatment before changing their dose or stopping Ozempic.
Can Ozempic cause serious stomach problems?
Yes. Although ordinary nausea or temporary gastrointestinal discomfort is relatively common, severe or persistent gastrointestinal symptoms require more attention.
Current US prescribing information warns that severe gastrointestinal adverse reactions have been reported with Ozempic. Semaglutide also delays gastric emptying.
Patients should contact their healthcare professional if stomach symptoms are severe or do not go away.
Ozempic and pancreatitis
Acute pancreatitis has been observed in patients treated with semaglutide. Pancreatitis is inflammation of the pancreas and can become a serious medical condition.
A key warning symptom is severe, persistent abdominal pain, which may sometimes radiate to the back and may occur with or without vomiting.
If pancreatitis is suspected, patients should seek prompt medical assessment. Treatment decisions should then be made by the healthcare professional responsible for the patient’s care.
Ordinary nausea or mild abdominal discomfort does not by itself mean that someone has pancreatitis, but severe and persistent pain should not be ignored.
Ozempic and gallbladder problems
Gallbladder problems, including gallstones and inflammation of the gallbladder, have been reported in people treated with Ozempic.
Symptoms that may indicate a gallbladder problem include:
- pain in the upper abdomen;
- fever;
- yellowing of the skin or eyes (jaundice); and
- pale or clay-coloured stools.
These symptoms warrant medical assessment rather than self-treatment at home.
Can Ozempic cause dehydration or kidney problems?
Ozempic does not simply cause kidney damage in most people who take it. However, gastrointestinal side effects can create an important indirect risk.
Persistent nausea, vomiting or diarrhoea can cause dehydration. Significant fluid loss can worsen kidney function, particularly in people who already have kidney disease or other risk factors.
Patients who cannot keep fluids down, have prolonged vomiting or diarrhoea, or develop signs of dehydration should contact a healthcare professional.
Ozempic and low blood sugar
Ozempic can lower blood glucose, but the risk of clinically important hypoglycaemia is particularly relevant when semaglutide is combined with insulin or an insulin secretagogue such as a sulfonylurea.
Symptoms of low blood sugar can include:
- sweating;
- shakiness;
- hunger;
- dizziness or light-headedness;
- confusion or drowsiness;
- headache;
- blurred vision;
- fast heartbeat; and
- weakness or feeling jittery.
A clinician may need to review the dose of insulin or a sulfonylurea when Ozempic is used alongside these medicines.
Can Ozempic affect the eyes?
There are two distinct eye-related issues worth understanding: diabetic retinopathy complications and non-arteritic anterior ischaemic optic neuropathy (NAION).
Diabetic retinopathy
Worsening diabetic retinopathy has been observed in some patients treated with semaglutide, particularly in people who already had diabetic retinopathy.
In a two-year cardiovascular outcomes trial involving patients with type 2 diabetes at high cardiovascular risk, diabetic retinopathy complications were reported in 3.0% of patients treated with semaglutide compared with 1.8% receiving placebo.
Rapid improvement in glucose control has long been associated with temporary worsening of diabetic retinopathy in some patients. People with a history of diabetic retinopathy should therefore be monitored appropriately while using Ozempic.
NAION and semaglutide
European regulators now list non-arteritic anterior ischaemic optic neuropathy (NAION) as a very rare side effect of semaglutide medicines including Ozempic.
NAION occurs when blood flow to the optic nerve is disrupted and can result in loss of vision.
After reviewing clinical-trial, post-marketing and epidemiological evidence, the European Medicines Agency’s safety committee concluded that NAION may affect up to 1 in 10,000 people taking semaglutide.
Several large epidemiological studies suggested approximately a two-fold relative increase in risk among adults with type 2 diabetes exposed to semaglutide, corresponding to approximately one additional case per 10,000 person-years of treatment.
Sudden loss of vision or rapidly worsening eyesight requires urgent medical attention. European guidance states that semaglutide should be stopped if NAION is confirmed.
Can Ozempic cause an allergic reaction?
Serious hypersensitivity reactions, including anaphylaxis and angioedema, have been reported with Ozempic.
Patients should seek emergency medical help for symptoms of a serious allergic reaction such as:
- swelling of the face, lips, tongue or throat;
- difficulty breathing or swallowing;
- severe rash or itching;
- fainting or severe dizziness; or
- a very rapid heartbeat.
Ozempic and thyroid tumours
US Ozempic prescribing information carries a boxed warning concerning thyroid C-cell tumours.
Semaglutide caused thyroid C-cell tumours in rodents. It is not known whether Ozempic causes thyroid C-cell tumours, including medullary thyroid carcinoma (MTC), in humans.
In the United States, Ozempic is contraindicated in people with a personal or family history of MTC and in people with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
Patients should discuss their personal and family medical history with their prescriber rather than interpreting the animal findings as evidence that Ozempic is known to cause thyroid cancer in humans.
Ozempic before surgery or anaesthesia
Ozempic delays gastric emptying. Rare reports of pulmonary aspiration have occurred in patients receiving GLP-1 receptor agonists who underwent procedures requiring general anaesthesia or deep sedation despite following pre-operative fasting instructions.
Patients should tell the surgical, anaesthesia and other healthcare teams that they use Ozempic before a planned operation or procedure.
Whether treatment should be changed before a procedure is an individual clinical decision. Patients should not stop prescribed Ozempic solely on the basis of general information found online.
What about long-term Ozempic side effects?
Questions about “long-term side effects” need to distinguish between known adverse effects observed during treatment and hypothetical problems that have not been established as caused by Ozempic.
Semaglutide has been studied in large clinical programmes and continues to be monitored after approval. Known risks and adverse reactions are updated in regulatory product information when sufficient evidence emerges. The addition of NAION to European semaglutide safety information illustrates how pharmacovigilance continues after a medicine reaches the market.
There is not a separate list of side effects that automatically appears after a person has taken Ozempic for a particular number of years. Instead, the relevant considerations include known adverse reactions, the patient’s underlying conditions, other medicines, treatment duration and emerging safety evidence.
Patients receiving long-term treatment should continue routine clinical monitoring appropriate to their diabetes and individual risk factors.
Does a higher Ozempic dose cause more side effects?
Side effects do not occur in a perfectly dose-dependent way for every patient, but gastrointestinal tolerability can be affected by dose and dose escalation.
For example, in the US placebo-controlled trial data, nausea was reported in 15.8% of patients receiving 0.5 mg and 20.3% receiving 1 mg. Vomiting was reported in 5.0% and 9.2%, respectively.
In a separate trial comparing Ozempic 1 mg with 2 mg, gastrointestinal adverse reactions occurred in 30.8% of patients receiving 1 mg and 34.0% receiving 2 mg.
This does not mean an individual patient will necessarily develop more side effects at a higher dose, but it reinforces the reason for gradual dose escalation and individual assessment of tolerability.
When should you seek medical help while taking Ozempic?
Patients should seek prompt or urgent medical assessment for symptoms that could indicate a serious adverse reaction.
| Symptom | Why it matters |
|---|---|
| Severe, persistent abdominal pain | Possible pancreatitis or another significant abdominal condition |
| Sudden loss of vision or rapidly worsening eyesight | Possible NAION or another urgent eye condition |
| Swelling of the face, lips, tongue or throat; breathing difficulty | Possible serious allergic reaction |
| Persistent vomiting or diarrhoea | Risk of dehydration and kidney problems |
| Upper abdominal pain with fever, jaundice or pale stools | Possible gallbladder disease |
| Symptoms of severe hypoglycaemia | Particularly relevant when Ozempic is combined with insulin or a sulfonylurea |
This list is not exhaustive. New, severe or rapidly worsening symptoms should be assessed according to their clinical seriousness rather than waiting for them to match a particular online list.
Ozempic side effects FAQ
What is the most common side effect of Ozempic?
Nausea is one of the most commonly reported Ozempic side effects. In US placebo-controlled trials, nausea occurred in 15.8% of patients receiving 0.5 mg and 20.3% receiving 1 mg, compared with 6.1% receiving placebo.
How long do Ozempic side effects last?
There is no fixed duration. Gastrointestinal symptoms are often most noticeable during treatment initiation and dose escalation and may improve with time. Persistent or severe symptoms should be discussed with a healthcare professional.
Does Ozempic cause diarrhoea?
Yes. Diarrhoea is a recognised common adverse effect of Ozempic. Persistent diarrhoea can lead to dehydration, so patients should seek medical advice if it is severe or does not resolve.
Does Ozempic cause constipation?
Yes. Constipation is another common gastrointestinal adverse reaction reported with Ozempic.
Can Ozempic cause pancreatitis?
Acute pancreatitis has been observed in patients treated with semaglutide. Severe and persistent abdominal pain, particularly if it radiates to the back, requires prompt medical assessment.
Can Ozempic damage your kidneys?
Kidney problems can occur particularly in the context of dehydration caused by prolonged nausea, vomiting or diarrhoea. People with existing kidney disease or significant gastrointestinal symptoms should discuss this with their healthcare professional.
Can Ozempic affect your eyesight?
Yes. Diabetic retinopathy complications have been observed with semaglutide, particularly in patients with pre-existing diabetic retinopathy. European regulators also classify NAION, which can cause sudden vision loss, as a very rare semaglutide side effect.
Does Ozempic cause thyroid cancer?
It is not known whether Ozempic causes thyroid C-cell tumours in humans. Semaglutide caused these tumours in rodents, which is the basis for the US boxed warning. Ozempic is contraindicated in the US in patients with a personal or family history of medullary thyroid carcinoma or MEN 2.
Should you stop Ozempic if you get side effects?
Not automatically. Mild gastrointestinal effects may improve, while some symptoms require prompt assessment. Patients should not change or discontinue prescribed treatment without medical advice unless they are experiencing an emergency requiring immediate care.
Related MediSearcher guides
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Reviewed by: Dr Mattias Hagman, PhD
Editorial review: MediSearcher reviews medication guides against current regulatory and primary medical sources. This page distinguishes US and European safety information where regulatory wording differs.
Last reviewed: 14 October 2026
Sources and verification
This guide was checked against current official prescribing and regulatory information available on 14 October 2026. Medication safety information can change as regulators evaluate new evidence, so patients should also check the current information supplied with their medicine.
- US Ozempic Prescribing Information — US Food and Drug Administration / Novo Nordisk
- Ozempic EPAR — European Medicines Agency
- Ozempic Product Information — European Medicines Agency
- PRAC conclusion on NAION and semaglutide — European Medicines Agency
This article is for general informational purposes and does not replace individual medical advice. Ozempic is a prescription medicine. Questions about side effects, treatment suitability or changes to prescribed treatment should be discussed with an appropriate healthcare professional.