Ozempic Side Effects: How Common They Are and When to Get Help

Ozempic is a once-weekly injection licensed in the UK for adults with type 2 diabetes. Its most common side effects are nausea and diarrhoea, mostly in the first months of treatment. This guide sets out how often each side effect happened in the trials, as reported in the UK product information, which effects need urgent attention and how to report them.

What Ozempic Is Licensed For

Adults with type 2 diabetes; it is not licensed in the UK for weight management.

Ozempic contains semaglutide. Its Summary of Product Characteristics (SmPC) licenses it for adults with type 2 diabetes that is not well controlled, alongside diet and exercise, either on its own when metformin is not suitable or with other diabetes medicines. It is not licensed in the UK for weight management.

The same medicine, semaglutide, is licensed for weight management under the brand Wegovy, at different doses and with its own product information. For those side effects, see Wegovy side effects.

Ozempic Side Effects at a Glance

Very common: nausea, diarrhoea and low blood sugar with insulin or a sulfonylurea.

The SmPC groups side effects by how often they happened in clinical trials:

• Very common (more than 1 in 10 people): feeling sick (nausea), diarrhoea, and low blood sugar (hypoglycaemia) when used with insulin or a sulfonylurea.

• Common (up to 1 in 10 people): vomiting, stomach pain, bloating, constipation, indigestion, inflamed stomach lining (gastritis), acid reflux, burping, wind, reduced appetite, dizziness, headache, tiredness, gallstones, weight loss, raised pancreatic enzymes, diabetic eye complications, and low blood sugar with other diabetes tablets.

• Uncommon (up to 1 in 100 people): allergic reactions such as rash, changes in taste, faster heart rate, acute pancreatitis, slower stomach emptying and injection site reactions.

• Rare (up to 1 in 1,000 people): severe allergic reaction (anaphylaxis).

• Very rare (up to 1 in 10,000 people): non-arteritic anterior ischaemic optic neuropathy (NAION), which affects the nerve of the eye.

Swelling under the skin (angioedema), blockage of the bowel and unusual skin sensations have been reported since it came onto the market, with frequency not known.

Stomach and Gut Side Effects

Nausea 17-19.9%, diarrhoea 12.2-13.3%, vomiting 6.4-8.4% at 0.5 mg and 1 mg; mostly early and mild to moderate.

Section 4.8 of the SmPC reports, for the 0.5 mg and 1 mg doses:

• Nausea: 17% and 19.9% of people.

• Diarrhoea: 12.2% and 13.3%.

• Vomiting: 6.4% and 8.4%.

Most were mild to moderate, short-lived and most common in the first months of treatment. They led 3.9% and 5% of people to stop. At 2 mg, nausea was similar to 1 mg, while diarrhoea and vomiting were more common. People with low body weight may get more stomach side effects.

Vomiting and diarrhoea can cause dehydration, which in rare cases can affect the kidneys, so keep drinking fluids and speak to your prescriber or a pharmacist if you cannot keep them down.

Low Blood Sugar

Severe low blood sugar happened mainly with a sulfonylurea or insulin, whose doses may be lowered.

Ozempic on its own rarely causes severe low blood sugar: no severe episodes were seen when it was used alone in the trials. The risk is higher with a sulfonylurea or insulin. Severe hypoglycaemia was reported in 1.2% of people taking it with a sulfonylurea and 1.5% with insulin.

That is why your prescriber may lower your sulfonylurea or insulin dose when you start, and you may need to check your blood sugar more often. The SmPC also warns that cutting insulin too quickly when starting this type of medicine has led to diabetic ketoacidosis in people who depend on insulin. Ozempic is not a substitute for insulin and is not used in type 1 diabetes.

Serious Side Effects: When to Get Help

Persistent, severe stomach pain, sudden loss of vision or a severe allergic reaction need urgent help.

• Acute pancreatitis was confirmed in 0.3% of people on semaglutide in the main trials (0.2% on comparators). Seek immediate medical attention for persistent, severe stomach pain. If pancreatitis is confirmed, Ozempic should not be restarted.

• Sudden loss of vision, even partial, needs urgent assessment by an eye specialist. The SmPC reports that large studies in adults with type 2 diabetes suggest semaglutide may be linked to about one additional case of NAION per 10,000 person-years of treatment (for example, 10,000 people each treated for a year).

• Diabetic eye complications: in a 2-year trial of people with long-standing, poorly controlled diabetes, they occurred in 3% on semaglutide and 1.8% on placebo, mainly in people on insulin with known diabetic retinopathy. People with pre-existing diabetic retinopathy should be monitored closely.

• Severe allergic reactions, such as swelling of the face or throat or difficulty breathing, need emergency help.

If you think you are having a serious reaction, call 999 or go to A&E. For urgent advice that is not an emergency, call NHS 111.

Other Side Effects

Gallstones, headache, dizziness and tiredness are common; injection site reactions are uncommon.

• Gallstones are common.

• Headache, dizziness and tiredness are common.

• Injection site reactions, such as a rash or redness, were reported by 0.6% of people on 0.5 mg and 0.5% on 1 mg, and were usually mild.

• Stopping because of side effects: 6.1% of people on 0.5 mg and 8.7% on 1 mg stopped because of an adverse event, against 1.5% on placebo, most often because of stomach side effects.

Pregnancy, Breastfeeding and Contraception

Use contraception; not in pregnancy or breastfeeding; stop at least 2 months before a planned pregnancy.

• Contraception: the SmPC recommends that women who could become pregnant use contraception while taking Ozempic.

• Pregnancy: Ozempic should not be used during pregnancy. If you want to become pregnant, stop it at least 2 months before, because it stays in the body for a long time.

• Breastfeeding: Ozempic should not be used while breastfeeding.

Before an Operation or Procedure

Tell the team you take Ozempic, because it slows stomach emptying.

Ozempic slows down how quickly the stomach empties. The SmPC notes reports of food or fluid being breathed into the lungs (pulmonary aspiration) in people taking this type of medicine who had a general anaesthetic or deep sedation. If you are due to have an operation or procedure, tell the team that you take Ozempic.

Thyroid Questions

Thyroid C-cell tumours were seen in rodents; the SmPC says relevance for humans is considered low.

In 2-year studies in rats and mice, semaglutide caused thyroid C-cell tumours. The SmPC describes this as a class effect of GLP-1 medicines in rodents, through a mechanism to which rodents are particularly sensitive, and says the relevance for humans is considered low but cannot be completely excluded. Tell your prescriber about your medical history before starting.

Reporting Side Effects

Tell your prescriber and report suspected side effects to the MHRA Yellow Card scheme.

Tell your prescriber, diabetes team or pharmacist about any side effect that bothers you or does not go away. You can also report suspected side effects to the MHRA Yellow Card scheme, online or through the Yellow Card app.

Frequently Asked Questions