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Semaglutide is the most discussed drug in recent years. As a GLP-1 receptor agonist, it was initially approved for type 2 diabetes (Ozempic®) and later also for the treatment of obesity (Wegovy®). The “slimming injection” enables an average weight loss of 15% in 68 weeks — more than any diet alone.
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GLP-1 agonists only under medical control. Not a lifestyle product. This article does not replace medical advice.
Semaglutide is the active substance behind Ozempic and Wegovy – two medications that have fundamentally changed the therapy of type 2 diabetes and obesity. With an average weight loss of 15% of body weight in 68 weeks (STEP-1 study), semaglutide is the most effective weight-reduction agent that has ever been clinically tested. On top of this comes a proven cardiovascular protection (SELECT study 2023): 20% fewer severe cardiovascular events in obese patients without diabetes.
| Property | Details |
|---|---|
| Active substance | Semaglutide |
| ATC code | A10BJ06 |
| Substance class | GLP-1 receptor agonist (incretin mimetic) |
| Trade names | Ozempic® (diabetes), Wegovy® (obesity), Rybelsus® (oral, diabetes) |
| Available forms | Pre-filled pen s.c. 1×/week; Rybelsus®: tablet daily |
| Half-life | About 7 days (hence 1×/week) |
| Maximum dose | Ozempic: 2 mg/week; Wegovy: 2.4 mg/week |
| Prescription status | Yes |
| Insurance reimbursement | Ozempic: yes (with diabetes). Wegovy: no (lifestyle medication!) |
| Special feature | On average 15% weight loss in 68 weeks (STEP studies) |
The question is justified – because the confusion is great: both contain exactly the same active substance semaglutide. The difference lies in the approval, the maximum dose, and the cost reimbursement. Ozempic was developed for type 2 diabetes and approved there. Wegovy was developed explicitly for obesity, in a higher dose (2.4 mg instead of max. 2 mg) and with weight loss as the primary endpoint.
| Ozempic® | Wegovy® | |
|---|---|---|
| Active substance | Semaglutide | Semaglutide (identical!) |
| Approved for | Type 2 diabetes | Obesity (BMI ≥ 30) or overweight (BMI ≥ 27) + comorbidity |
| Maximum dose | 2 mg/week | 2.4 mg/week |
| Weight loss | About 5–7% (a side effect) | About 15% in 68 weeks (the main goal) |
| Insurance reimbursement | Yes (with diabetes) | No (lifestyle medication) |
| Cost (self-payer) | About 170–300 €/month | About 300–500 €/month |
Since Ozempic became known through social media trends (above all in the USA) as the "weight-loss jab of the stars", many doctors use it off-label for weight loss in people without diabetes. This has concrete consequences: Ozempic was at times no longer available in Germany in 2022/2023 – because non-diabetics bought up the packs approved for diabetics. People with type 2 diabetes, who rely on Ozempic for their blood sugar control, could no longer get their medication. The right place for weight reduction with semaglutide is Wegovy – for which there is a separate approval and a separate supply channel.
GLP-1 (glucagon-like peptide-1) is a hormone that the gut releases after a meal. It signals to the body: "Food has been eaten, produce insulin, reduce glucagon, slow the gastric emptying." In nature, GLP-1 is broken down within minutes. Semaglutide is a pharmacologically optimised version of GLP-1 – structurally changed so that it binds to albumin in the blood and therefore acts for about 7 days.
The strongest effect of semaglutide is not in the stomach, but in the brain. GLP-1 receptors also sit in the hypothalamus – the appetite and satiety centre. There, semaglutide reduces the feeling of hunger and suppresses cravings – particularly for calorie-rich, highly processed foods. Many patients report that food suddenly seems "less interesting" or that they are full after small amounts. This is not willpower – this is pharmacology.
| Mechanism of action | Effect |
|---|---|
| Insulin stimulation (glucose-dependent) | Better blood sugar control – only with raised blood sugar, hardly any hypoglycaemia! |
| Glucagon inhibition | Less sugar release from the liver |
| Slowed gastric emptying | Full for longer after eating |
| Appetite centre in the brain | Reduced feeling of hunger, fewer cravings |
| Cardiovascular protection | Fewer heart attacks and strokes (SUSTAIN-6, SELECT study) |
| Indication | Preparation | Requirements |
|---|---|---|
| Type 2 diabetes | Ozempic® (s.c.) / Rybelsus® (oral) | In addition to diet + exercise; after/with metformin |
| Obesity (BMI ≥ 30) | Wegovy® | + dietary change + exercise |
| Overweight (BMI ≥ 27) + comorbidity | Wegovy® | E.g. high blood pressure, sleep apnoea, dyslipidaemia |
| Cardiovascular risk reduction | Wegovy® | SELECT study: 20% fewer cardiovascular events |
The step-by-step dose increase (titration) is not optional with semaglutide – it is decisive for tolerability. The most common side effect (nausea) occurs above all with a too-fast dose increase. Anyone who keeps to the titration steps experiences considerably fewer gastrointestinal complaints.
| Week | Dose (1×/week) | Note |
|---|---|---|
| Week 1–4 | 0.25 mg | Introduction phase – not a therapeutic active dose |
| Week 5–8 | 0.5 mg | – |
| Week 9–12 | 1.0 mg | – |
| Week 13–16 | 1.7 mg | – |
| From week 17 | 2.4 mg | Maintenance dose – the therapeutic goal |
The most common side effects of semaglutide are gastrointestinal and arise through the slowed gastric emptying. They are temporary in most patients – they improve markedly after 4–8 weeks. Two rarer but clinically important side effects deserve particular attention: gallstones and muscle loss.
| Side effect | Frequency | Note |
|---|---|---|
| Nausea | Very common (>40%) | Above all with a dose increase. Mostly improves after 4–8 weeks |
| Diarrhoea | Common | – |
| Constipation | Common | Drink enough! |
| Vomiting | Common | Small meals, eat slowly |
| Headaches / fatigue | Common | – |
| Gallstones | Occasional | Through fast weight loss. Caution: biliary colic! |
| Pancreatitis | Rare | Severe abdominal pain → see a doctor at once! |
| NAION (a rare eye disease) | Very rare | The EMA is investigating (2025). An eye doctor check is recommended |
| Thyroid tumours | Unclear (animal study!) | Increased in rodents; not confirmed in humans. MTC family history = a contraindication! |
| Muscle loss | Noteworthy | About 30–40% of the weight loss! Protein + strength training! |
This is the side effect that is talked about the least – although it is significant in the long term. When people lose weight on semaglutide, a considerable part of it is not fat mass, but muscle mass. Studies show that about 30–40% of the total weight loss is muscle mass. This is not specific to semaglutide – it is a general consequence of calorie-restricted weight loss. But the extent of the weight loss on semaglutide makes it clinically relevant.
What muscle loss means: less strength and endurance, in the long term an increased risk of sarcopenia (muscle wasting in old age), a lower basal metabolic rate (makes future weight control harder), and an increased fall risk in older patients. The countermeasures are clear and documented: a protein-rich diet (1.2–1.5 g protein per kg of body weight daily) and regular strength training throughout the entire therapy. Anyone who only takes the jab without these accompanying measures does not optimise the result.
This is the uncomfortable truth about semaglutide – and the information that most patients receive too late: after stopping, most people quickly regain the weight.
Semaglutide does not combat a cause of obesity – it modulates hormone signals that regulate hunger and satiety. As long as it is in the body, less is eaten. When it is stopped, the original hunger signals come back – often more intensely than before, because the body has reacted to calorie restriction. Studies (the STEP-4 withdrawal study) show: patients who, after 68 weeks on semaglutide, switched from the active dose to placebo regained, on average, about two thirds of the lost weight within a year.
