Close-up of a GLP-1 weight loss injection pen on a clean clinical surface with soft lighting
Semaglutide is a widely studied GLP-1 receptor agonist used for weight loss in Singapore. It is made by Novo Nordisk.
This guide tells you how the treatment works, who can use it, what to expect, side effects, costs, and how it compares to other options.
The STEP 1 trial gives us clinical data. It was published in the _New England Journal of Medicine_ (Wilding JPH, et al. N Engl J Med 2021;384:989-1002).
What Is Semaglutide and How Does It Work?
Semaglutide is injected once a week. It is a GLP-1 receptor agonist. GLP-1 is made in your body after you eat. It does not last long. This medication is a longer-lasting version. It stays active for about 7 days.
It works in three ways:
- Controls hunger: It tells your brain to feel less hungry. This helps with food cravings.
- Slows stomach emptying: Food stays in your stomach longer. This makes you feel full longer.
- Controls blood sugar: It helps release insulin. Insulin controls blood sugar after meals.
This GLP-1 treatment only targets one receptor. Other medicines target two. One example is tirzepatide (Mounjaro). Targeting two receptors may help with more weight loss.
Bar chart showing STEP 1 trial weight reduction targets achieved with semaglutide vs placebo at 68 weeks
How Semaglutide Compares to Other GLP-1 Weight Loss Medications
| Feature | Semaglutide | Tirzepatide (Mounjaro) | Liraglutide (Saxenda) |
| Receptor targets | GLP-1 only | GLP-1 + GIP (dual) | GLP-1 only |
| Injection frequency | Once weekly | Once weekly | Once daily |
| Weight reduction | -14.9% at 68 weeks | -20.2% at 72 weeks | -8% at 56 weeks |
| Trial | STEP 1 (NEJM 2021) | SURMOUNT-5 (NEJM 2025) | SCALE (NEJM 2015) |
| Cardiovascular data | SELECT trial: 20% CV event reduction | Pending (SURMOUNT-MMO) | Limited |
Semaglutide has been around longer than tirzepatide. This means we know more about its safety. We also have more data about heart health. The SELECT trial showed good results. It showed a 20% drop in heart problems. No other weight loss medicine has shown this (SELECT trial, NEJM 2023).
Who Is a Suitable Candidate?
You need a prescription for this GLP-1 medication. A doctor will check if it is right for you. They will ask about your health history. They will also ask about your weight goals.
Here are the general rules:
- Must be 18 years or older.
- BMI of 30 or higher (obesity). BMI is a measure of body fat. Or BMI of 27 or higher with one of these:
- High blood pressure
- High cholesterol
- Sleep problems
- Heart problems
- Type 2 diabetes or prediabetes
- Must have tried to lose weight before without success. This means using diet and exercise. Talk to a doctor to find out if you qualify.
Who might not be able to use it:
- People with a history of thyroid cancer. This includes family history.
- People with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
- People with a history of pancreatitis (swelling of the pancreas).
- Women who are pregnant or breastfeeding. This also includes women planning to get pregnant.
- People already taking another GLP-1 medicine.
- People with glycated haemoglobin of 6.5% or higher (diabetes).
What to Expect During Treatment
Dosing Schedule
The treatment starts with a low dose. Then, it increases slowly over 16 weeks.
- Weeks 1-4: 0.25 mg per week (starting dose)
- Weeks 5-8: 0.5 mg per week
- Weeks 9-12: 1.0 mg per week
- Weeks 13-16: 1.7 mg per week
- Week 17 onward: 2.4 mg per week (regular dose)
The slow increase helps with side effects. If side effects are bad at 2.4 mg, your doctor may keep you at 1.7 mg.
How the Injection Works
The medicine comes in a pen. It is injected under the skin (subcutaneously). You can inject in the stomach, thigh, or arm. Change the injection spot each week. It takes less than a minute.
Clinic Visits
Your doctor will want to see you often. They will check your weight, BMI, and waist size. They will also check for side effects. They may also check your blood.
Infographic showing semaglutide dosing schedule from 0.25mg to 2.4mg over 16 weeks
Expected Results and Timeline
The STEP 1 trial gives us these results. There were 1,961 people in the trial. It lasted 68 weeks.
| Timeframe | What to Expect |
| Weeks 1-4 | You will start to feel less hungry. |
| 3-6 months | You will start to see weight loss. This is when most changes happen. |
| 68 weeks | People lost about 14.9% of their weight (15.3 kg). |
Weight Reduction Targets Achieved (STEP 1)
| Target | Semaglutide | Placebo |
| ≥5% body weight | 86.4% | 31.5% |
| ≥10% body weight | 69.1% | 12.0% |
| ≥15% body weight | 50.5% | 4.9% |
| ≥20% body weight | 32.0% | 1.7% |
About 69% of people lost at least 10% of their weight. How well it works depends on many things. These include your starting weight, diet, and exercise.
Additional Health Improvements
- Waist size went down 13.54 cm (compared to 4.13 cm with placebo).
- Blood pressure went down 6.16 mmHg.
- Most people with prediabetes had normal blood sugar again.
Side Effects and Safety
The STEP 1 trial tells us about the side effects.
Common Side Effects
| Side Effect | Semaglutide (n=1,306) | Placebo (n=655) |
| Nausea | 44.2% | 17.4% |
| Diarrhoea | 31.5% | 15.9% |
| Vomiting | 24.8% | 6.6% |
| Constipation | 23.4% | 9.5% |
| Headache | 15.2% | 12.2% |
| Dyspepsia | 10.3% | 3.5% |
| Abdominal pain | 10.0% | 5.5% |
Most side effects are not too bad. They happen when the dose is increased. They usually get better as your body gets used to the medicine.
Treatment Discontinuation
About 7% of people stopped taking the medication because of side effects. Only 3.1% of people stopped taking the placebo. Most people stopped because of stomach problems.
Serious Side Effects (Rare)
- Serious side effects: 9.8% with semaglutide vs 6.4% with placebo
- Gallbladder problems: 2.6% vs 1.2%
- Pancreatitis: 3 cases (0.2%) in the semaglutide group
- Death: 1 in each group (not related to the treatment)
When to Contact Your Doctor
- Bad stomach pain that does not stop
- Signs of an allergic reaction
- Symptoms of low blood sugar
- Throwing up a lot
Cost of Semaglutide Treatment in Singapore
The cost changes from clinic to clinic. Here is a general idea:
| Component | Estimated Cost |
| Initial consultation | $50 – $150 |
| Monthly medication | ~$600 – $800 per month |
| Follow-up consultations | $50 – $100 per visit |
The cost depends on the dose, time of treatment, and clinic fees. Blood tests also add to the cost. Insurance usually does not cover this treatment in Singapore.
Horizontal bar chart comparing common side effects of semaglutide vs placebo from STEP 1 trial
Semaglutide vs Tirzepatide: Which GLP-1 Treatment Is Right for You?
People often ask this question. Here is what the science shows:
| Metric | Semaglutide | Tirzepatide |
| Weight reduction | -14.9% (STEP 1) | -20.2% (SURMOUNT-5) |
| Cardiovascular outcomes | 20% CV event reduction (SELECT) | Data pending |
| GI discontinuation rate | 4.5% | 2.7% |
| Safety track record | 5+ years of data | Newer (less long-term data) |
| Cost in Singapore | ~$600-$800/month | ~$600-$1,500/month |
Neither medicine is “better” for everyone. Semaglutide has better heart data. Tirzepatide helps more with weight loss in studies. Your doctor can help you decide. They will look at your health, weight goals, and budget.
Read our companion guide to Tirzepatide (Mounjaro) in Singapore.
Tips for Supporting Your Treatment
- Eat meals with lots of protein. This keeps your muscles strong.
- Eat slowly and stop when you are full.
- Drink lots of water (at least 2 litres each day).
- Try to be active for 150 minutes each week.
- Lift weights 2-3 times a week.
- Go to all your follow-up appointments.
- Write down what you eat for the first few weeks.
- Some patients also benefit from body contouring treatments alongside weight loss.
Questions to Ask Your Doctor Before Starting
- Can I use this medicine based on my weight and health?
- What dose will I start on? How long until I reach the regular dose?
- What side effects should I look out for?
- How does this medicine compare to other choices for me?
- How much will this cost in total?
- What happens if I stop taking the medicine?
- How often will I need to see you?
A good visit should feel like a talk, not a sales pitch. Your doctor should explain things clearly. They should give you time to think.
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Frequently Asked Questions
How much weight can I lose on Ozempic?
People lost about 15.3 kg (14.9% of body weight) in a study. This was over 68 weeks. About 86% lost at least 5% of their weight. How well it works depends on you.
How soon will I see results on Ozempic?
Most people feel less hungry in the first few weeks. You will start to see weight loss after 3 to 6 months.
Is semaglutide the same as Ozempic?
Yes. Semaglutide is the active ingredient. Ozempic is the name of the medicine. Wegovy is another version. It has a higher dose.
Can I take Ozempic for weight loss without having diabetes?
Yes. Wegovy is for weight loss. It is for adults who are overweight. It is also for adults with weight-related problems.
What is the difference between Ozempic and Wegovy?
Both have semaglutide. Ozempic is for diabetes. Wegovy is for weight loss. Wegovy has a higher dose.
Is Ozempic safe for long-term use?
Yes. Studies show it helps with weight loss for 2 years. Another study followed people for 40 months. It showed no new safety problems.
What happens when I stop taking Ozempic?
You may gain weight back. One study showed people gained back about two-thirds of the weight. It is important to have a plan with your doctor.
How does Ozempic compare to Mounjaro?
One study showed Mounjaro helped with more weight loss. But Ozempic has better data for heart health.
Do I need a prescription for Ozempic in Singapore?
Yes. You need a prescription from a doctor.
What are the most common Ozempic side effects?
The most common side effects are nausea, diarrhea, and vomiting. Some people also have constipation. These usually get better over time.
How much does Ozempic cost per month in Singapore?
It costs about $600 to $800 each month. The cost depends on the dose and clinic. It does not include doctor visits or blood tests. Insurance usually does not cover it.
Can Ozempic help reduce belly fat?
Yes, it can help. People in a study had smaller waist sizes. But the medicine works on your whole body. It does not just target belly fat.
What foods should I avoid while taking Ozempic?
Avoid foods high in fat and sugar. These can make nausea worse. Eat smaller meals. Drink lots of water. Your doctor may tell you to eat more protein.
Can I drink alcohol while on Ozempic?
It is okay to drink a little. But it can increase the risk of nausea. It can also cause low blood sugar. Talk to your doctor about alcohol.
How long do I need to take Ozempic for weight loss?
One study lasted 68 weeks. Another lasted 2 years. It works best as a long-term plan. Stopping the medicine may cause you to gain weight back.
What is the difference between Ozempic and Saxenda?
Both are GLP-1 medicines. But they have different active ingredients. Ozempic is a shot once a week. Saxenda is a shot once a day. Ozempic helps with more weight loss.
Is Ozempic available in Singapore?
Yes. But it can be hard to find. Talk to your doctor about the best choice for you.
References
- Wilding JPH, Batterham RL, Calanna S, et al. Once-weekly semaglutide in adults with overweight or obesity. _N Engl J Med_. 2021;384:989-1002. (STEP 1)
- Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes. _N Engl J Med_. 2023;389:2221-2232. (SELECT)
- Garvey WT, et al. Two-year effects of semaglutide in adults with overweight or obesity. _Nat Med_. 2022;28:2083-2091. (STEP 5)
- Rubino D, et al. Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance. _JAMA_. 2021;325:1414-1425. (STEP 4)
- ClinicalTrials.gov: STEP 1 (NCT03548935)
This article is just for learning. It is not medical advice. Talk to a doctor to see if semaglutide is right for you.
