Semaglutide: the active substance in Ozempic, Wegovy and Rybelsus

How does semaglutide work in your body?

Semaglutide works in three places at once: in your brain, in your stomach and in your pancreas. That explains why you eat less on it and why your blood sugar becomes more stable.

• Brain: semaglutide activates the GLP-1 receptors in the satiety centre. You feel full sooner and the constant feeling of hunger decreases.
• Stomach: the stomach empties more slowly, so a meal "stays with you" longer and you get hungry again less quickly.
• Pancreas: after a meal, more insulin and less glucagon are released. As a result, your blood sugar drops after eating.

Natural GLP-1 is broken down within a few minutes. Semaglutide has been modified so that it stays active in your body for about a week. That is why one injection a week is enough with Ozempic and Wegovy. Want to know how a substance works that acts on two hormone receptors at once? Then read about tirzepatide, the active substance in Mounjaro.

Ozempic, Wegovy and Rybelsus: three brands, one active substance

Ozempic, Wegovy and Rybelsus all contain semaglutide, but they differ in form of administration, dose and official indication. Ozempic and Rybelsus are licensed for type 2 diabetes. Wegovy is licensed for weight management in overweight. That is the most important distinction.

The licences, strengths and reimbursement conditions per brand are in the semaglutide monograph of the Farmacotherapeutisch Kompas (the Dutch national medicines reference) of Zorginstituut Nederland (the Dutch National Health Care Institute), consulted September 2026.

So: is semaglutide the same as Ozempic? Semaglutide is the substance, Ozempic is a brand name. Ozempic contains semaglutide, but not all semaglutide is Ozempic. Wegovy contains the same substance at a higher maximum dose and is the only one of the three licensed for weight loss. You can read more about that difference in our article on Wegovy vs Ozempic.

Semaglutide pill or injection: what is the difference?

Semaglutide as a pill exists: Rybelsus is a tablet you take every day. You use the injections (Ozempic and Wegovy) once a week. The substance is the same; the difference lies in absorption and dose.

A semaglutide tablet is only absorbed to a limited extent in the stomach. That is why you take Rybelsus on an empty stomach with a sip of water and then wait half an hour before eating, drinking or taking other medicines. An injection goes directly into the fatty tissue under the skin and does not have that limitation.

Rybelsus is licensed for type 2 diabetes, not for weight loss. Whether a tablet suits your situation is for the doctor to assess. How that works is covered in our article on the Ozempic pill.

Semaglutide and weight loss: what research shows

You can lose weight with semaglutide, and this has been investigated in large studies. In the STEP 1 study (NEJM, 2021), adults with overweight or obesity, without diabetes, received 2.4 mg of semaglutide or a placebo weekly for 68 weeks, alongside lifestyle support. The semaglutide group lost an average of 14.9 percent of their body weight, the placebo group 2.4 percent.

These are averages from controlled studies. How much weight you lose varies from person to person and depends on your dose, your starting weight, your diet, your exercise and whether you keep taking the medicine. The Cochrane review from October 2025 adds two caveats: the manufacturer was involved in 17 of the 18 studies, and in the long term more people probably stop because of side effects. Read more about Ozempic eyes.

You usually notice the effect on your hunger in the first weeks, certainly from the higher doses. Your weight then follows gradually.

Tried everything and still not managing to lose weight? Your own BIG-registered doctor (the BIG register is the Dutch register of healthcare professionals) assesses whether medical weight loss is right for you and supports you personally. Medical weight loss with injections →

Side effects and drawbacks of semaglutide

The most common side effects of semaglutide are nausea, diarrhoea, constipation and vomiting. According to apotheek.nl, the patient information website of the Dutch pharmacists' organisation KNMP, these symptoms usually disappear within 4 weeks. Headache and tiredness also occur.

The gastrointestinal symptoms mainly occur during the period in which you build up the dose. That is why you always start low and the doctor increases the dose step by step. Smaller portions, eating slowly and limiting fatty food help many users through that phase.

Other drawbacks to be aware of:

• Hypoglycaemia: blood sugar that is too low can occur if you combine semaglutide with insulin or sulphonylureas. Without that combination, the risk is small.
• Pregnancy: you do not use semaglutide if you are pregnant or want to become pregnant.
• Rare side effects: inflammation of the pancreas and gallstones are rare but have been described. If you have severe, persistent abdominal pain, contact your doctor straight away.
• Weight regain: after stopping, the appetite returns and many people regain weight. That is why treatment includes a plan for diet and exercise.

Do you suspect a side effect? Report it to Bijwerkingencentrum Lareb (the Netherlands Pharmacovigilance Centre). A detailed overview of the side effects is in our article on Ozempic side effects.

Who is semaglutide for and how do you get it in the Netherlands?

In the Netherlands, semaglutide is only available on prescription. A doctor prescribes it and a registered Dutch pharmacy supplies it. For weight management, the licensing threshold is a BMI of 30 or higher, or 27 or higher with a weight-related condition such as high blood pressure, type 2 diabetes or sleep apnoea.

Whether medical weight loss with semaglutide is right for you is assessed by the doctor. They look at your BMI, your medical history, your other medicines and factors such as a wish to become pregnant or a previous inflammation of the pancreas.

Can a GP prescribe semaglutide? Yes, in type 2 diabetes this happens regularly. For overweight without diabetes, GPs are reluctant and usually refer you first to a combined lifestyle intervention (gecombineerde leefstijlinterventie). How that works is covered in our article on whether your GP can prescribe weight loss injections.

Be careful with offers outside the pharmacy. Web shops that sell "semaglutide peptide" or loose vials without a prescription are outside regulatory oversight and regularly supply counterfeit or impure products. Offers via Marktplaats (the Dutch classifieds site) or foreign websites are also illegal and unsafe. The safe route is covered in our article on how to buy semaglutide.

What does semaglutide cost and is it reimbursed?

Semaglutide is not covered by basic health insurance (basisverzekering) for weight loss. Ozempic and Rybelsus are only reimbursed under conditions in type 2 diabetes; Wegovy is not included in the medicines reimbursement system (Farmacotherapeutisch Kompas, September 2026). If you use semaglutide to lose weight, you pay for the medication yourself. Read more about whether Ozempic is covered by insurance.

The pharmacy prices per strength and the reimbursement conditions are in our articles on the Ozempic price and weight loss medication covered by insurance.

At Qlinic, a programme with semaglutide (Ozempic) costs €250 per month, plus a one-off €400 support fee. That includes the prescription, home delivery through a registered Dutch pharmacy and support from your own doctor, with a follow-up every 4 weeks. We do not offer Wegovy. Everything about how the programme is structured is on the page about medical weight loss with injections.

Want to know whether medical weight loss is right for you? Take the short check and the doctor will assess your situation. Eligibility check →

Frequently asked questions about semaglutide

Is semaglutide the same as Ozempic?

Semaglutide is the active substance, Ozempic is a brand name. Ozempic contains semaglutide, as do Wegovy and Rybelsus. The brands differ in form, dose and official indication.

What does semaglutide do to your body?

Semaglutide curbs your appetite via the satiety centre in the brain, slows your gastric emptying and increases insulin release after a meal. As a result, you eat less and your blood sugar becomes more stable.

How much weight do you lose with semaglutide?

In the STEP 1 study, participants lost an average of 14.9 percent of their body weight in 68 weeks with 2.4 mg of semaglutide per week, compared with 2.4 percent on placebo. How much you lose varies from person to person and depends on dose, diet, exercise and starting weight.

How fast do you lose weight with semaglutide?

You usually notice the reduced appetite in the first weeks. Your weight then drops gradually, because the dose is built up in steps. Read more in our article on how fast does Ozempic work.

What are the drawbacks of semaglutide?

The most frequently reported drawbacks are nausea, diarrhoea, constipation and vomiting, especially during the build-up. Inflammation of the pancreas and gallstones are rare. After stopping, many people regain weight.

Can a GP prescribe semaglutide?

Yes, a GP may prescribe semaglutide and regularly does so in type 2 diabetes. For overweight without diabetes, GPs are reluctant and often refer you to a lifestyle programme first.

How do I get semaglutide?

Only through a doctor's prescription and a registered Dutch pharmacy. A doctor first assesses whether the medicine suits you. Offers without a prescription, via web shops, Marktplaats or from abroad, are illegal and often counterfeit.

How much does semaglutide cost?

When you use it to lose weight, you pay for semaglutide yourself; basic health insurance does not cover it in that case. The pharmacy price depends on the brand and strength. At Qlinic, a programme with semaglutide (Ozempic) costs €250 per month, plus a one-off €400 support fee.

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