A GLP-1 receptor agonist for diabetes and weight management
Semaglutide
A GLP-1 medicine for type 2 diabetes and, separately, for weight management — usually a weekly injection, with an oral form also available.
What is Semaglutide?
Semaglutide is a GLP-1 receptor agonist used to help control blood sugar in type 2 diabetes and, under a different brand, to support weight management. It lowers blood sugar, reduces appetite and slows stomach emptying so you feel fuller for longer.
Education and reference only. This is a plain-language guide to Semaglutide — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Semaglutide is a GLP-1 receptor agonist used to help control blood sugar in type 2 diabetes and, under a different brand, to support weight management. It lowers blood sugar, often helps with weight loss, and has been shown to reduce certain heart and kidney risks in people with type 2 diabetes. In the UK the diabetes injection is branded Ozempic, an oral (tablet) version for diabetes is Rybelsus, and the higher-strength weight-management injection is Wegovy. Supply has at times been limited, and the brands are intended for their licensed uses rather than being interchangeable.
How it works
Semaglutide mimics GLP-1, a natural gut hormone released after eating. It prompts the body to release more insulin and less glucose-raising hormone when blood sugar is high, slows how quickly the stomach empties, and acts on the brain's appetite centres to increase fullness. Together these effects lower blood sugar and tend to reduce appetite and food intake, which is why it also supports weight loss. Because the blood-sugar effect works mainly when sugar is raised, it carries a low risk of hypos on its own.
Company & origin
Originated / developed by: Novo Nordisk.
Semaglutide is a GLP-1 receptor agonist developed by Novo Nordisk in Denmark (inventors including Jesper Lau and Thomas Kruse) and first approved by the FDA in December 2017 as Ozempic for type 2 diabetes, later as Rybelsus and Wegovy.
What it treats
Conditions Semaglutide is used for
Practical use
How to take Semaglutide
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is most often given as a once-weekly injection under the skin of the abdomen, thigh or upper arm, on the same day each week; a daily tablet form is also available.
- If you use the oral form, take it on an empty stomach with a small sip of plain water, then wait before eating, drinking or taking other medicines.
- Nausea is common, especially early on; it usually settles, and eating smaller, lower-fat meals can help.
- It is usually started low and increased gradually to reduce side effects.
- Use it alongside a healthy diet and physical activity for the best results.
- Stop and seek urgent advice for severe, persistent stomach pain, which can rarely signal inflammation of the pancreas.
Weighing it up
Advantages & disadvantages of Semaglutide
Advantages
- Effectively lowers blood sugar and supports weight loss.
- Once-weekly injection is convenient for many people.
- Low risk of causing low blood sugar when used alone.
- Has shown benefits for heart health in some groups.
Disadvantages
- Commonly causes nausea, vomiting, diarrhoea and constipation, especially early on.
- Can rarely cause inflammation of the pancreas and gallbladder problems.
- Can be costly and has at times been in short supply.
- Given by injection in its weekly form, which some people dislike, and weight may return if it is stopped.
Practical use
Good to know
Most forms are given as a once-weekly injection under the skin, while Rybelsus is a daily tablet taken on an empty stomach with a little water. Nausea is common when starting or increasing the dose and usually eases with time; building up slowly helps. It is not a treatment for type 1 diabetes. The injection brands differ by licensed use — Ozempic and Rybelsus for type 2 diabetes, Wegovy for weight management — and should be used as prescribed. A rare but important risk is pancreatitis: severe, persistent tummy pain spreading to the back, often with vomiting, should prompt stopping and urgent advice. Gallstones can also occur.
Who should not take it / use with caution
- People with type 1 diabetes — it is not a treatment for type 1.
- People who have had pancreatitis (inflammation of the pancreas) before, or a serious allergic reaction to semaglutide.
- Avoided in pregnancy and when planning pregnancy or breastfeeding, and used with care in severe gut or stomach-emptying problems.
Monitoring
- Blood glucose and HbA1c (in diabetes) and weight/waist (in weight management)
- Kidney function, especially if vomiting or diarrhoea cause dehydration
- For severe tummy pain or gallstone symptoms
Side effects
- Nausea, vomiting, diarrhoea or constipation, especially early on — usually easing as the body adjusts.
- Reduced appetite, indigestion or burping; injection-site reactions with the injectable forms.
- Rarely, pancreatitis (severe ongoing tummy pain — stop and seek urgent help), gallstones, dehydration from vomiting/diarrhoea, or changes in vision in people with diabetic eye disease.
Key interactions
- The risk of hypos rises when combined with insulin or a sulfonylurea (such as gliclazide), so those doses may be reduced.
- By slowing stomach emptying it can change how quickly some other tablets are absorbed.
- Tell your prescriber about all your medicines, including the oral contraceptive and any taken on an empty stomach (relevant to the oral form).
Available as: A once-weekly injection given under the skin using a pre-filled pen, and a daily tablet (the oral form) taken on an empty stomach.
Answers
Semaglutide: frequently asked questions
What is the difference between Ozempic, Rybelsus and Wegovy?
All three contain semaglutide but are licensed for different uses. Ozempic is the weekly injection for type 2 diabetes, Rybelsus is the daily tablet for type 2 diabetes, and Wegovy is a higher-strength weekly injection for weight management. They are prescribed for their specific licensed purpose rather than swapped freely.
Is semaglutide an injection or a tablet?
Both forms exist. Ozempic and Wegovy are once-weekly injections under the skin, while Rybelsus is a daily tablet taken on an empty stomach with a little water. Which one you have depends on what you are being treated for and your preferences.
Why do I feel sick when I start it?
Nausea is common when starting semaglutide or increasing the dose, because it slows stomach emptying and affects appetite. It usually settles as your body adjusts, and building up the dose gradually, with smaller meals, helps. Tell your team if it is severe or persistent.
Can it be used for type 1 diabetes?
No. Semaglutide is for type 2 diabetes (and, as Wegovy, weight management) — it is not a treatment for type 1 diabetes, which always needs insulin. Using it in type 1 would not provide the insulin that is essential.
What is the difference between semaglutide and its brand names?
They are the same active ingredient — semaglutide is the generic (active-ingredient) name, and Ozempic, Rybelsus and Wegovy are brand names for its different licensed forms and uses. The active ingredient is identical across them.
The wider class
About GLP-1 receptor agonists
Semaglutide belongs to the glp-1 receptor agonists class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
Browse by body system
Authoritative sources
- BNF: Semaglutide.
- electronic Medicines Compendium (SmPC): Semaglutide (Ozempic, Rybelsus, Wegovy).
- NICE NG28: Type 2 diabetes in adults; NICE technology appraisals for weight management.
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