GLP-1 in Singapore: How It Works for Weight Loss

It Isn't Just Willpower: How GLP-1 Medicines Work With Your Fullness Signal

22 October 2026 Weight Loss, GLP-1 8-Minute Read
Information reviewed by: Dr Lye Tong Fong, MBBS (S'pore) Family Physician
Last updated:

GLP-1 medicines work with your body's own “I'm full” hormone to quieten hunger, so smaller portions feel like enough. This guide explains how they work, the results seen in clinical trials, the side effects, and who they may suit.

What Is GLP-1?

GLP-1 (glucagon-like peptide-1, also written GLP1) is a hormone your gut releases after eating that tells your brain you're full. GLP-1 medicines copy this hormone to reduce appetite and help with weight loss.

The natural hormone carries one message to your brain: food has arrived, you can stop now. A sister hormone, GIP, works alongside it — together they are known as incretins.2

In many people living with excess weight, the after-meal rise in GLP-1 is smaller than usual. This may help explain persistent hunger and constant thoughts about food — what many patients call “food noise”. GLP-1 medicines turn that signal back up — as the animation shows.

▶ How GLP-1 works
Gut GLP-1 Hungry Full Brain
1 · You eatYour gut senses food and releases GLP-1 and GIP.
2 · Signal travelsThe hormones reach your brain's appetite centre, and your stomach empties more slowly.
3 · Dial turnsHunger quietens, you feel satisfied sooner, and fullness lasts longer.

A volume knob, not an off switch. GLP-1 medicines don't stop you eating — they turn the volume of hunger down, so sensible portions feel like enough. The habits still have to be built, which is why they work alongside a reduced-calorie diet and regular activity.

Why “eat less, move more” so often stalls

Most people who struggle with weight have tried hard, often many times. When you cut calories, your body turns hunger hormones up and fullness hormones down, and your metabolism slows a little. This is called metabolic adaptation — it's why the last few kilos feel so stubborn and the first few come back so easily. It isn't a character flaw.1

Think of a thermostat. Your brain defends a certain body weight — its “set point” — somewhat like a thermostat set to 25°C. Dieting hard is like opening the windows: the room cools for a while, then the heater kicks in to bring it back to 25°C. Lasting weight loss often means helping your brain accept a lower setting, not just opening the windows.

▶ The rebound
Weight Time → Your set point Diet: weight falls Body fights back

Illustration of a common pattern, not data from a specific study. Individual results vary.

GLP-1 Weight Loss: What Results to Expect

In large clinical trials, adults on once-weekly GLP-1 injections lost an average of about 15–21% of their body weight over 68–72 weeks, compared with around 2–3% on placebo — alongside diet and exercise.5,6 Individual results vary.

You don't need to reach a “perfect” weight to feel the difference. For an 85 kg adult:

5%≈ 4 kg A meaningful first goal — less strain on your knees and joints.
10%≈ 8.5 kg Many people report more energy and find it easier to move.
15%+≈ 13 kg The average range reached in the trials above, over about 16–17 months.

How long does GLP-1 take to work?

  • Weeks 1–4

    You start on the lowest dose. Many people notice a smaller appetite and less “food noise” within the first few weeks.

  • Months 2–4

    Your doctor steps the dose up about every four weeks, if you're coping well. Weight loss becomes steady and gradual.

  • Months 6–18

    Weight keeps falling, more slowly over time, then levels off. In the trials, weight loss continued throughout, slowing in the final months as it approached a plateau.5,6

  • Long term

    You and your doctor agree a plan to keep the weight off — staying on treatment, which is the best-proven way to maintain your loss, or coming off it with support.

Questions about your weight? A doctor can help.

Speak to a Doctor

GLP-1 Medicines for Weight Loss

Two GLP-1 medicines are commonly used for weight management. Both are prescription-only, once-weekly injections. A doctor can advise whether either is suitable for you.

Semaglutide

Acts on GLP-1. Once-weekly injection.

Tirzepatide

Acts on GLP-1 and GIP. Once-weekly injection.

Who Can Take GLP-1 for Weight Loss?

GLP-1 medicines may be considered for adults who meet either of these:

BMI 30 or above

A doctor will check whether a GLP-1 medicine is suitable for you.

BMI 27–29.9

A doctor will assess whether a GLP-1 medicine is suitable for you.

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For Asians, health risks begin to rise from a BMI of 23, and from a waist of 90 cm (men) or 80 cm (women).3,4 GLP-1 medicines may be considered from a BMI of 27, after a doctor's assessment.

Not suitable if you are pregnant, or if you or a family member has had medullary thyroid cancer or MEN2 (multiple endocrine neoplasia type 2).

Needs a closer discussion with your doctor if you:

  • have had pancreatitis
  • have gallbladder disease
  • have severe gut problems such as gastroparesis
  • are breastfeeding, or planning a pregnancy (the medicine needs to be stopped well beforehand — usually at least 2 months for semaglutide)

Why GLP-1 Treatment Needs a Doctor's Supervision

GLP-1 medicines are prescription-only, and they aren't a one-off prescription. Medical supervision helps keep treatment safe:

  • Before starting: a doctor reviews your health history and current medicines, and checks for reasons it may not be suitable (see “Who Can Take GLP-1 for Weight Loss?” above). Blood tests may be needed — for example cholesterol, liver, kidney and thyroid.
  • Starting gradually: the dose is usually started low and increased step by step, which helps reduce side effects such as nausea.
  • Regular follow-up: a doctor checks your weight and how you're coping with the medicine, adjusts the dose where needed, and manages any side effects early. Reviews are often every few months at first, then less often once things are stable.
  • Protecting muscle: eating and strength training are reviewed, since some muscle can be lost along with fat.

Eating and Exercise on GLP-1

GLP-1 medicines make healthy habits easier to keep — they don't replace them. No strict dieting is needed:

Keep your local favourites

Chicken rice or nasi lemak can stay on the menu — in smaller portions, with more vegetables on the side.

Protein and fibre first

Eggs, fish, tofu, lean meat and vegetables at each meal help protect muscle and keep you full.

Strength training twice a week

Most of the weight lost is fat, but some muscle goes too — strength training and enough protein help limit this.

150+ minutes of activity a week

Brisk walking counts. Build up towards 300 minutes for the best results.7

GLP-1 Side Effects

Common — usually mild

Nausea Feeling full Diarrhoea Constipation Vomiting Headache Tiredness Injection-site redness

Most common when starting or stepping up a dose, and tend to ease. Smaller, less greasy meals and plenty of water help.

See a doctor promptly if you have

  • Severe, persistent stomach pain (possible pancreatitis)
  • Upper-right belly pain or yellowing skin (gallbladder)
  • Swelling, rash or difficulty breathing (allergy)
  • Vomiting or diarrhoea that won't settle (dehydration)

Big meals, especially early on, make nausea worse — stop eating when you feel full. Because GLP-1 medicines slow stomach emptying, tell your doctor and anaesthetist well before any surgery or procedure that needs sedation — they will advise on preparation (such as a liquid diet beforehand) and whether to pause the medicine. Not a complete list — your doctor will go through the risks of your medicine with you.

Key takeaways

  • GLP-1 is a gut hormone that tells your brain you're full. GLP-1 medicines copy it to turn hunger down.
  • They work alongside a reduced-calorie diet and regular activity, not instead of them.
  • In large trials, adults lost an average of about 15–21% of their body weight over 68–72 weeks, compared with 2–3% on placebo. Individual results vary.
  • They are prescription-only, and may be considered from a BMI of 27 after a doctor's assessment.
  • Nausea is the most common side effect; some symptoms need prompt medical attention.

Speak to a doctor about weight management

If you're struggling with your weight, a doctor can look at the whole picture — your health, your habits and the options that may suit you.

Speak to a Doctor Find a Clinic

Frequently Asked Questions

What is GLP-1?

GLP-1 (glucagon-like peptide-1) is a hormone your gut releases after eating that tells your brain you're full. GLP-1 medicines copy this hormone to reduce appetite and slow how quickly the stomach empties, helping with weight loss alongside a reduced-calorie diet and regular activity. They are prescription-only.

How much do GLP-1 injections cost in Singapore?

The cost depends on the medicine and the dose prescribed, and is usually charged per weekly injection. GLP-1 medicines for weight management are generally self-paid and not claimable under MediSave or CHAS. Ask the clinic to confirm the full cost before you start.

Who qualifies for GLP-1 weight loss treatment?

GLP-1 medicines may be considered for adults with a BMI of 27 or above, alongside a reduced-calorie diet and regular activity. They are prescription-only, and a doctor will assess whether one is suitable for you.

Can I see a doctor about GLP-1 online?

Yes. In Singapore, a doctor can assess you by video consultation. They may ask for blood tests or an in-person review before deciding whether a GLP-1 medicine is suitable.

Is there a GLP-1 pill instead of an injection?

GLP-1 medicines also exist as tablets. The medicines described on this page are once-weekly injections. A doctor can explain which options may suit you.

How quickly does GLP-1 work for weight loss?

Many people notice a smaller appetite within the first few weeks. Weight loss is gradual, because the dose is built up slowly, about every four weeks. In large trials, weight loss continued throughout the 68–72 weeks of treatment, slowing in the final months as it approached a plateau. Individual results vary.

Where can I buy GLP-1 safely in Singapore?

GLP-1 medicines can only be supplied with a doctor's prescription from a licensed clinic or hospital — they are not sold over the counter. Avoid online sellers and overseas websites: injections bought this way may be counterfeit, contaminated or wrongly dosed.

What happens when I stop GLP-1?

Appetite usually returns, and weight tends to come back if treatment and lifestyle support stop. That doesn't mean treatment has failed — weight is a long-term condition that often needs long-term care. The habits you build during treatment matter most, and your doctor will plan with you how long to stay on treatment and how to come off it.

References

  1. Sumithran P, et al. Long-term persistence of hormonal adaptations to weight loss. N Engl J Med 2011;365:1597–1604.
  2. Drucker DJ. Mechanisms of action and therapeutic application of glucagon-like peptide-1. Cell Metab 2018;27:740–756.
  3. WHO Expert Consultation. Appropriate body-mass index for Asian populations. Lancet 2004;363:157–163.
  4. Lau DCW, et al. Health Promotion Board–Ministry of Health clinical practice guidelines: obesity. Singapore Med J 2016;57:292–300.
  5. Wilding JPH, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med 2021;384:989–1002.
  6. Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med 2022;387:205–216.
  7. Bull FC, et al. WHO 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med 2020;54:1451–1462.

This article is general health education and does not replace advice from your own doctor. GLP-1 medicines are prescription-only; a doctor will assess whether one is suitable for you. Results vary between individuals.

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