In short
- One pathway, several brands. All these medicines copy a gut hormone called GLP-1. The brand names differ, the chemistry mostly does not.
- What they do. Quieten appetite, slow the stomach, steady blood sugar.
- Same rules for all of them. Same side effect pattern, same people who must not take them.
- Not a replacement for the rest. They are licensed alongside eating and activity changes, not instead of them.
- Long term by nature. Stopping without a plan means the weight comes back.
Treatment Overview
What is GLP-1?
GLP-1 stands for glucagon like peptide 1, a hormone your gut releases after you eat.
It does four things: it prompts insulin release when blood sugar is high, it suppresses glucagon, it slows how fast the stomach empties, and it signals fullness to the brain.
Your own GLP-1 lasts a couple of minutes. These medicines mimic that signal for a whole week.
Which medicines are in this class?
| Ingredient | Sold as | Acts on |
|---|---|---|
| Semaglutide | Wegovy for weight, Ozempic for diabetes | GLP-1 |
| Tirzepatide | Mounjaro and related brands | GLP-1 and GIP |
| Liraglutide | Daily injection brands | GLP-1 |
Newer options include an oral semaglutide tablet and a daily oral non peptide agent. Availability differs by country and changes quickly.
How much do they achieve?
In the trials, average weight loss over roughly 15 months ran from about 15 percent with semaglutide 2.4 mg to about 21 percent with tirzepatide 15 mg, against about 3 percent on placebo with the same lifestyle programme.
Averages hide a wide range. Some people lose far more. A minority lose very little, and for them the plan changes rather than the dose climbing forever.
The rule that applies to all of them
The usual checkpoint is three months on a proper dose. If you have not lost roughly 5 percent of your body weight by then, the medicine is not working for you and something else is tried.
That rule protects you from spending a year and a lot of money on a medicine that was never going to suit you.
What if a GLP-1 is not right for you?
There are other licensed options with different mechanisms, including phentermine with topiramate, naltrexone with bupropion, and orlistat. They are generally less effective for weight but each suits particular situations, and each has its own contraindications.
Metabolic and bariatric surgery is also a legitimate option for people who meet the criteria, and it is discussed rather than avoided.
Who Is a Good Candidate?
- Your body mass index is 30 or above, or 27 and above with a weight related condition such as type 2 diabetes, high blood pressure, sleep apnoea or fatty liver.
- Serious diet and activity changes have not produced or held a result.
- You want to understand the class before committing to a brand.
- You accept that this is long term treatment with regular review.
- You or a close relative have had medullary thyroid cancer, or you have multiple endocrine neoplasia type 2. The whole class is ruled out.
- You are pregnant, trying to conceive or breastfeeding.
- You have had pancreatitis, severe inflammatory bowel disease or gastroparesis.
- You expect the medicine to work without any change to how you eat and train.
- You are considering compounded semaglutide or tirzepatide from an unregulated source.
What Happens During the Consultation
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1
What you actually want
The goal, the history, what has been tried and what happened. How your appetite behaves through the day. Pregnancy plans and contraception, because none of these medicines are used in pregnancy.
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2
Whether the class fits
Examination, weight and body composition, blood pressure and blood work. Full medication review, and personal and family history of thyroid cancer, pancreatitis and gallbladder disease.
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3
Which agent, and why
If a GLP-1 based medicine fits, the choice between them is made on your comorbidities, your cardiovascular risk, availability and your preference on oral versus injection. The reason is stated, not implied.
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4
The plan
Starting dose, escalation steps, the three month checkpoint, a protein and training target, what to do about side effects and the review dates.
Program Structure & Follow-Up
How the dose is built up
Every medicine in this class starts low and climbs in steps, usually four weeks apart. That is not caution for its own sake. Starting high is what produces the nausea stories.
Each step is a decision. If a step is not tolerated, you stay where you are longer or move back down. Many patients settle below the maximum dose and stay there.
What follow up looks like
- Every four to six weeks while the dose climbs.
- Every two to three months once you are stable. Weight, body composition, blood pressure and blood work.
- Between appointments. Direct access through the membership programmes.
Protecting muscle
Across studies of this class, close to a third of the weight lost came from muscle related measures. Muscle loss beyond the expected amount is the main avoidable harm of fast weight loss.
- A daily protein target set to your body weight.
- Resistance training at least twice a week.
- Body composition measured alongside the scale.
What happens when you stop
Appetite returns and the weight follows. Across studies people regain around 0.4 kg a month after stopping, with most returning close to their starting weight within about two years.
That is the argument for deciding how you will stop before you start.
Benefits, Limits & Safety
Side effects, the shared pattern
- Common. Nausea in roughly a quarter to 40 in 100 patients. Vomiting, diarrhoea or constipation in around 10 to 20 in 100. Usually mild to moderate, worst after a dose increase, and improving with time.
- Uncommon but serious. Gallbladder disease, pancreatitis, bowel obstruction.
What helps
- Smaller meals, more often, stopping at the first sign of fullness.
- Eating slowly.
- Low fat, low grease and low spice in the days after an injection.
- Enough fluid.
- Delaying or reversing a dose step when it is not tolerated.
When to call
- Severe stomach pain going through to the back, especially with vomiting.
- Vomiting you cannot stop.
- Pain under the right ribs, or yellow skin or eyes.
- Any change in vision if you have diabetes.
Who must not take them
- Anyone pregnant or breastfeeding.
- Anyone with a personal or family history of medullary thyroid cancer, or multiple endocrine neoplasia type 2.
- Used with caution or not at all after pancreatitis, and in severe inflammatory bowel disease or gastroparesis.
Two practices avoided here
- Compounded versions. Mixed outside a regulated manufacturer, without the safety, quality and effectiveness review the licensed products go through. Harm has been reported.
- Microdosing. Staying deliberately on a tiny dose has not been studied, gives unpredictable results and invites dosing errors.
Before surgery
Tell the anaesthetist you take a GLP-1 medicine. Slower stomach emptying raises the risk during anaesthesia and they may want you to hold a dose.
What the class achieves
Average weight loss in trials of roughly 15 to 21 percent over about 15 months depending on the agent and dose, against about 3 percent on placebo. Individual results vary widely.
How you are followed
Review every four to six weeks during dose escalation, then every two to three months. A defined three month checkpoint decides whether the medicine continues.
When the class is ruled out
Pregnancy, breastfeeding, personal or family history of medullary thyroid cancer, multiple endocrine neoplasia type 2. Caution or refusal after pancreatitis, and in severe inflammatory bowel disease or gastroparesis.
Cost & Program Investment
Cost depends on which medicine, which dose and how long you stay on treatment, so a single number on a website would be misleading. You get the full figure in the consultation before anything is prescribed, and there are no charges you have not been told about. What is included is the assessment, the blood work, the escalation plan, the reviews and access between appointments through the membership programmes.
Frequently Asked Questions
They share a pathway, a side effect pattern and a list of contraindications. They differ in the molecule, the dose, how often you inject or take them, what they are licensed for and how much weight they produce in trials. Tirzepatide also acts on a second receptor.
For weight loss alone, tirzepatide has the highest trial numbers, with semaglutide close behind. But if you have cardiovascular disease without diabetes, semaglutide is the one with proven heart benefit in that group. Best depends on your case, not on a league table.
Poorly. They are licensed alongside a reduced calorie diet and more activity, and the trials were run that way. The medicine makes the change possible. It does not replace it.
About three months on a proper dose. If you have not lost roughly 5 percent of your body weight by then, the plan changes rather than the dose climbing indefinitely.
Some, yes. Across studies close to a third of the weight lost came from muscle related measures. That is why protein and resistance training are part of the plan from day one and body composition is measured.
They have been studied over years and are approved for long term use. Digestive side effects are common and usually settle. Serious problems such as pancreatitis are uncommon. Safe means correctly selected and properly monitored.
You can, but expect the weight to return without something else in place. Obesity behaves like a long term condition, so these are usually long term medicines. If there is a good reason to stop, it is planned before you start.
Oral options exist and more are arriving. Availability differs by country and changes quickly, so what can actually be prescribed here is checked at the consultation rather than promised on a website.
There are other licensed medicines with different mechanisms, including phentermine with topiramate, naltrexone with bupropion and orlistat. They are generally less effective but suit particular situations.
Usually, and that is the whole appeal. It is also mixed outside a regulated manufacturer without the safety, quality and effectiveness review the licensed product goes through, and harm has been reported. It is not prescribed here.
No. They are not used in pregnancy or while breastfeeding and are stopped well before a planned pregnancy. If you could become pregnant, contraception is part of the conversation before you start.
It depends on the medicine, the dose and the duration, so a single figure would be misleading. You get the full cost in the consultation before anything is prescribed, because you should decide with the real number in front of you.
Evidence
Where this information comes from
Every figure on this page is taken from the sources below. All of them are free to read, so you can check them yourself.
- Wegovy: European public assessment report
- Mounjaro: European public assessment report
- Semaglutide for managing overweight and obesity
- Obesity and overweight
This page is general medical information and does not replace a personal consultation. Trial results are averages across large groups, not a prediction for any one person.