Semaglutide

Is semaglutide safe?

For most adults with type 2 diabetes or obesity, the evidence says the benefits outweigh the risks. Semaglutide, sold as Ozempic and Rybelsus for diabetes and as Wegovy for weight loss and heart protection, lowers blood sugar, typically produces weight loss of around 15% at the Wegovy dose, and in the SELECT trial of 17,604 people with heart disease and excess weight it cut heart attacks, strokes and cardiovascular deaths by about a fifth.

The trade-offs are side effects that many people feel, a set of uncommon but serious risks, and a track record of under ten years. We score it 72, between metformin, the older diabetes drug, and the higher-risk medicines on our list.

Stomach side effects: the price of the effect

Semaglutide slows the stomach and reduces appetite, so gut symptoms are part of how it works. In the Wegovy weight trials:

Side effect	Wegovy 2.4 mg	Placebo
Nausea	44%	16%
Diarrhoea	30%	16%
Vomiting	24%	6%
Constipation	24%	11%

They are worst during dose increases and usually ease. Doses go up every 4 weeks to limit them. Severe or persistent vomiting matters because dehydration can injure the kidneys.

The serious risks on the label

• Pancreatitis. Uncommon, but occasionally severe. In January 2026 the MHRA strengthened the warning for all GLP-1 drugs: it had 1,296 UK Yellow Card reports of pancreatitis with them between 2007 and October 2025, 19 of them fatal, against about 25.4 million packs dispensed in the previous five years. In the Wegovy weight trials, confirmed acute pancreatitis occurred at 0.2 cases per 100 patient-years, against under 0.1 on placebo. Severe upper stomach pain, often spreading to the back, needs urgent care.
• Gallbladder disease. Gallstones affected 1.6% of adults on Wegovy injection against 0.7% on placebo, and 2.5% against 1% with the tablets, partly because of rapid weight loss.
• Aspiration during anaesthesia. Food can stay in the stomach longer, so tell any surgical or endoscopy team you take it.
• Diabetic eye disease. Rapid improvement in blood sugar was linked to worsening retinopathy in one trial, so people with existing retinopathy need monitoring.
• Low blood sugar when combined with insulin or a sulfonylurea.

In 2025 the European Medicines Agency concluded that NAION, a sudden loss of vision in one eye from reduced blood flow to the optic nerve, is a very rare side effect affecting up to 1 in 10,000 people. Sudden vision loss needs urgent medical attention.

The boxed warningBoxed warningThe strongest safety warning the US FDA puts on a medicine's label, printed inside a black border at the top.More in the glossary is about thyroid C-cell tumours, which semaglutide caused in rodents. Human relevance is unknown, but it is not used in people with a personal or family history of medullary thyroid cancer or MEN 2.

Doses and versions

Product	Use	Maximum dose (US label)
Ozempic injection	Type 2 diabetes, heart and kidney protection	2 mg once a week
Rybelsus or Ozempic tablets	Type 2 diabetes	Taken daily on an empty stomach
Wegovy injection	Weight, heart risk, fatty liver disease (MASH)	2.4 mg weekly, or 7.2 mg (Wegovy HD) if tolerated
Wegovy tablets	Weight and heart risk	25 mg once a day

Tablets and injections are not interchangeable milligram for milligram. The FDA approved Wegovy tablets on 22 December 2025. The dose starts at 1.5 mg a day and steps up every 30 days through 4 mg and 9 mg to 25 mg. Each tablet is taken in the morning on an empty stomach with up to 4 ounces of water, then nothing to eat, drink or swallow for 30 minutes. In the 64-week tablet trial, people lost 13.6% of their body weight against 2.4% on placebo, with side effects similar to the injection's. In the UK, Rybelsus moved to new strengths in late 2025 (1.5, 4 and 9 mg replacing 3, 7 and 14 mg) with the same effect.

How does it compare with tirzepatide and orforglipron?

	Semaglutide (Wegovy)	Tirzepatide (Zepbound, Mounjaro)	Orforglipron (Foundayo)
Form	Weekly injection or daily tablet	Weekly injection	Daily tablet, no food or water rules
First US approval	2017	May 2022	April 2026
Our score	72	70	65

In the only head-to-head trial, SURMOUNT-5, 751 adults with obesity but without diabetes took the highest tolerated dose of either injection for 72 weeks. Weight fell by 20.2% on tirzepatide and 13.7% on semaglutide; stomach side effects were the most common in both groups and mostly came while doses were rising. We score tirzepatide slightly lower for its shorter record and because it can make the contraceptive pill less reliable. Orforglipron is easier to take but has more interactions and a far shorter record.

Compounded and fake semaglutide

During the 2022 to 2025 shortage, compounding pharmacies sold their own versions in multi-dose vials. The FDA reported hospitalisations from dosing errors, including people drawing up 5 to 20 times the intended dose, often by confusing units with milligrams or millilitres. Counterfeit pens have also been found: by October 2023 the MHRA had seized 369 suspected fake Ozempic pens, and some fake Ozempic and Saxenda pens contained insulin, which can cause dangerously low blood sugar. In February 2026 the MHRA found falsified Mounjaro 15 mg pens (batch D873576) sold by one UK online pharmacy, a reminder that any weight-loss pen bought outside the licensed supply can be fake. The safest source is a licensed pharmacy dispensing an approved product.

Who should be careful

Talk to your doctor or pharmacist before starting semaglutide if you have had pancreatitis, gallbladder disease, diabetic eye disease, kidney disease, severe gastroparesis, or a family history of medullary thyroid cancer. It should be stopped at least 2 months before a planned pregnancy, according to the Wegovy label. People taking insulin or a sulfonylurea may need their doses adjusted by their prescriber.

How we scored it

Dependence (95) and interactions (80) are strong. Regulatory warnings (50) reflect the rodent-based boxed warningBoxed warningThe strongest safety warning the US FDA puts on a medicine's label, printed inside a black border at the top.More in the glossary and FDA alerts on compounded products, and track record (70) its short time on the market. Serious side effects (65) is the key factor: very common stomach effects and uncommon but serious problems such as pancreatitis and gallbladder disease.