Medically reviewed by Dr. Chorphut Lorchutnopphakhun (Dr. Neem), General Practitioner, HealthDeliver.
Semaglutide is a GLP-1 receptor agonist: a medicine that mimics a naturally occurring gut hormone to reduce appetite, slow digestion and lower blood sugar. Ozempic, Wegovy and Rybelsus all contain it. They differ in dosage, in whether you inject it or swallow it, and in what each is licensed to treat.
For weight loss, the dose matters most. In the main trial, Wegovy’s 2.4 mg weekly dose produced an average loss of 14.9% of body weight over 68 weeks.
In this article
What Is Semaglutide? A GLP-1 Receptor Agonist in Three Brands
Semaglutide is a medication made by Novo Nordisk. Semaglutide is the active ingredient; Ozempic, Wegovy and Rybelsus are brand names. It was first approved as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. Weight reduction in those trials led to the Wegovy licence for chronic weight management.
Natural GLP-1 (glucagon-like peptide-1) breaks down within minutes. Semaglutide is engineered to last about a week, which is why the injections, given by the subcutaneous route, are taken on the same day each week.
In Thailand, Ozempic has been available for managing type 2 diabetes for several years. Novo Nordisk told Reuters it received Thai FDA approval for Wegovy in 2023 and launched it in April 2025, for adults with a BMI over 30 or overweight adults with a weight-related condition. All three are prescription-only.
How Semaglutide Works to Support Weight Loss
Semaglutide works by mimicking a naturally occurring hormone called GLP-1, which your gut releases after eating. Semaglutide functions in three places, and together they affect both appetite and blood sugar.
In the brain: appetite regulation
GLP-1 receptors in the hypothalamus and brainstem are involved in appetite. When semaglutide binds to them, it acts as a hormone that signals fullness, so satiety arrives sooner. Many patients describe “food noise” going quiet.
In the stomach: slower gastric emptying
Semaglutide slows gastric emptying, so a meal leaves the stomach more slowly and you feel fuller for longer. This is also why nausea is the most common side effect, especially after a large or fatty meal.
How does semaglutide affect blood sugar, insulin and glucagon?
When blood glucose rises, semaglutide prompts the pancreas to release insulin and reduces glucagon, the hormone that pushes sugar up. This lowers blood sugar levels in people with type 2 diabetes. Because the insulin response depends on glucose being high, semaglutide on its own rarely causes hypoglycaemia.
Does Ozempic burn fat or just suppress appetite?
It mainly suppresses appetite. The weight loss comes from eating less, not from burning fat directly or speeding up metabolism. Protein and resistance exercise still matter, so the weight you lose is fat rather than muscle.
Semaglutide Dosage: Ozempic vs Wegovy vs Rybelsus
Every semaglutide brand starts low and steps up slowly, usually every 4 weeks, so your digestive system can adjust. A dose may be increased only once the current one is tolerated.
| Ozempic | Wegovy | Rybelsus | |
|---|---|---|---|
How it is taken | Weekly injection | Weekly injection | Daily tablet |
Starting dose | 0.25 mg | 0.25 mg | 1.5 mg |
Usual maintenance dose | 0.5–1 mg (up to 2 mg) | 2.4 mg | 4–9 mg |
Licensed for | Type 2 diabetes | Chronic weight management | Type 2 diabetes |
Ozempic dosage
Ozempic starts at 0.25 mg once a week for 4 weeks, then 0.5 mg. If more blood sugar control is needed, the dose may be increased to 1 mg and then 2 mg, staying on each step for at least 4 weeks.
Wegovy dosage
Wegovy climbs through 0.25, 0.5, 1, 1.7 and 2.4 mg, each step lasting 4 weeks. It is the only semaglutide brand approved for weight management, and its 2.4 mg dose is what the weight-loss trials tested.
Rybelsus dosage
Rybelsus is semaglutide as a tablet: 1.5 mg orally once daily for 30 days, then 4 mg, with 9 mg if needed. Only a small fraction is absorbed, so take it on an empty stomach with up to 120 ml of water and wait 30 minutes before eating. These strengths replaced the older 3, 7 and 14 mg tablets in late 2025.
Semaglutide for Weight Loss: How Much Weight Can You Expect to Lose?
At the Wegovy dose, average semaglutide weight loss is around 15% of body weight over 68 weeks. Results depend heavily on dose and on whether you have diabetes.
The STEP 1 trial (Wilding et al., New England Journal of Medicine, 2021) gave 1,961 adults without diabetes semaglutide 2.4 mg or placebo for 68 weeks, alongside diet and exercise support. The semaglutide group lost 14.9% of body weight on average, against 2.4% on placebo.
Does semaglutide work for people without diabetes?
Yes. STEP 1 enrolled only people without diabetes, and that is where the largest losses are seen. People with type 2 diabetes tend to lose less: in SUSTAIN 7 (Pratley et al., Lancet Diabetes & Endocrinology, 2018), adults on Ozempic 1 mg lost 6.5 kg over 40 weeks from an average 95 kg.
How long does semaglutide take to work for weight loss?
Appetite often changes within the first few weeks, but weight loss builds slowly while the dose rises over about 16 weeks. In STEP 1, weight kept falling until around week 60 before levelling off.
What happens when you stop?
In the STEP 1 extension (Wilding et al., Diabetes, Obesity and Metabolism, 2022), people who stopped semaglutide regained about two-thirds of their lost weight within a year, and blood pressure and blood sugar improvements reversed too. Semaglutide works best as a long-term treatment for metabolic health.
Effects of semaglutide beyond body weight
The SELECT trial (Lincoff et al., New England Journal of Medicine, 2023) followed more than 17,000 adults with overweight or obesity and heart disease. Over an average of 33 months, semaglutide 2.4 mg cut the risk of major cardiovascular events (heart attack, stroke or cardiovascular death) by 20% compared with placebo.
Side Effects of Semaglutide
The most common semaglutide side effects are gastrointestinal: nausea, diarrhoea, constipation, vomiting and stomach pain. Tiredness and headaches are also reported. They are usually worst when starting or increasing a dose and ease over a few weeks.
Less common but serious risks include:
- Pancreatitis: severe, persistent stomach pain that may spread to the back needs urgent attention
- Gallbladder problems, including gallstones, more likely with rapid weight loss
- Dehydration and kidney strain if vomiting or diarrhoea is severe
- Low blood sugar when combined with insulin or sulfonylureas
Who is a good candidate for semaglutide?
Good candidates are adults with a BMI over 30, overweight adults with a weight-related condition, or people with type 2 diabetes who need better blood sugar control. It is not suitable with a personal or family history of medullary thyroid cancer or MEN2, or in pregnancy or breastfeeding; stop at least two months before a planned pregnancy. A history of pancreatitis or an eating disorder needs careful discussion first.
Compounded Semaglutide vs Branded Medicine
Compounded semaglutide is a version mixed by a pharmacy rather than made by Novo Nordisk. It spread in the US during Ozempic and Wegovy shortages.
The US FDA warns that compounded products are not reviewed for safety, effectiveness or quality. By November 2024 it had received more than 392 adverse event reports linked to compounded semaglutide, some involving hospital stays after dosing errors. Some products use salt forms, such as semaglutide sodium, that are not the same ingredient as the approved medicine.
HealthDeliver prescribes branded, Thai FDA-registered semaglutide only.
Getting Semaglutide Prescribed in Bangkok
In Thailand, semaglutide is prescription-only, and pens need refrigeration until first use, so avoid buying them online.
Bangkok’s large private hospitals prescribe semaglutide well, and existing patients there may prefer to stay. HealthDeliver’s difference is access and follow-through: no hospital wait, and the same doctor reviewing your progress as the dose increases. A first appointment covers:
- Your weight history, goals, medical history and current medicines
- Baseline blood tests where needed, such as HbA1c, lipids, kidney and liver function
- Which brand and dose suit you, or whether another GLP-1 agonist such as tirzepatide (Mounjaro) fits better
- Follow-up appointments to adjust the dose and manage side effects
Consultations are available in person at our Asok (BTS Asok / MRT Sukhumvit), Sathorn (BTS Chong Nonsi) and Phrom Phong (BTS Phrom Phong) clinics, or by telehealth. Consultation fee: ฿500.
Conclusion on Semaglutide
Ozempic, Wegovy and Rybelsus are one GLP-1 medicine in three forms; the brand sets the dosage, the route and the licence. The strongest weight-loss evidence sits with the Wegovy dose, and results last only as long as treatment and habits do.
The right choice depends on your health, goals, and the benefits and risks for you. This article is not medical advice: book a consultation with a healthcare provider who will stay with you as the dose changes.
Frequently Asked Questions About Semaglutide
These are the questions patients ask us most often about semaglutide.
What are the potential side effects of taking semaglutide?
Most side effects are digestive: nausea, vomiting, diarrhoea, constipation and stomach pain, usually worst during dose increases. Rarer risks include pancreatitis, gallbladder problems and kidney strain from dehydration. Report severe or persistent stomach pain to a doctor straight away.
Can Ozempic be used for weight loss?
Ozempic is licensed for type 2 diabetes, but doctors sometimes prescribe it off-label for weight. Wegovy contains the same semaglutide at a higher 2.4 mg dose and is the version licensed for weight management, so it is usually the first choice when weight is the main goal.
How does Ozempic work?
Ozempic mimics GLP-1, a gut hormone released after meals. It reduces appetite in the brain, slows how quickly the stomach empties, and helps the pancreas release insulin when blood sugar is high. It is injected once a week.
What organ is Ozempic bad for?
No single organ is routinely harmed, but the pancreas, gallbladder and kidneys need watching. Ozempic carries a small risk of pancreatitis and gallstones, and severe vomiting or diarrhoea can strain the kidneys through dehydration. Thyroid tumours were seen in rodent studies, so it is avoided in people with a history of medullary thyroid cancer.
What is known as the “poor man’s Ozempic”?
Berberine, a plant supplement from the barberry shrub, is often called the “poor man’s Ozempic” or “nature’s Ozempic” on social media. It is not a GLP-1 medicine. Small studies show some effect on blood sugar, but there is no strong evidence it produces meaningful weight loss, and it can interact with other medicines, including metformin.
What is the difference between Ozempic and Wegovy?
Both contain semaglutide and are injected once a week. Ozempic is licensed for type 2 diabetes at up to 2 mg a week, while Wegovy is licensed for weight management and goes up to 2.4 mg. Wegovy’s higher dose is the one tested in the main weight-loss trials.
Do you have to take semaglutide forever?
Not necessarily, but most people regain weight after stopping. In the STEP 1 extension, two-thirds of lost weight returned within a year. Any plan to reduce or stop should be made with your doctor, alongside lasting changes to diet and activity.
Does semaglutide reduce insulin?
No. Semaglutide increases insulin release, but only when blood sugar is high, and it lowers glucagon at the same time. In people with type 2 diabetes, better blood sugar control and weight loss can reduce how much insulin medication they need, which a doctor adjusts.
Can I lose 20 lbs in 2 months on semaglutide?
Unlikely for most people. The first two months are spent on the lowest starting doses, and in STEP 1 the average loss of 14.9% took 68 weeks. Losing 20 lbs (about 9 kg) in eight weeks would be faster than the trial averages, and rapid loss raises the risk of gallstones and muscle loss.
About HealthDeliver
HealthDeliver is a doctor-led medical clinic with branches in Asok, Sathorn and Phrom Phong, Bangkok. Our English- and Thai-speaking doctors offer in-clinic and telehealth consultations without hospital waiting times. We provide medically supervised weight management, from assessment and blood testing to ongoing follow-up.
Sources
- Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). New England Journal of Medicine, 2021
- Wilding JPH et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: the STEP 1 trial extension. Diabetes, Obesity and Metabolism, 2022
- Lincoff AM et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT). New England Journal of Medicine, 2023, summary by the American College of Cardiology
- Semaglutide for type 2 diabetes, including SUSTAIN 7 results. Australian Prescriber review, 2019
- US FDA: FDA’s concerns with unapproved GLP-1 drugs used for weight loss
- Middleton J. Weight loss fad berberine (“nature’s Ozempic”) lacks rigorous evidence, has potential harms. American Family Physician community blog, 2023
- Reuters: Novo Nordisk’s obesity drug Wegovy debuts in Thailand, April 2025 (via PharmaLive)
- MHRA Drug Safety Update: Rybelsus transition to new formulation, December 2025