> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hi-doctor.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# Semaglutide
> What semaglutide is, how the GLP-1 mechanism works, what STEP 1 reported, and what a doctor checks before prescribing it for weight loss.
Semaglutide is a medicine given as an injection under the skin once a week. It copies a natural gut hormone called GLP-1 that your body makes after eating, so you feel full sooner and stay full longer, and most people end up eating less.
## What it is
In the EU, the product authorised for weight management is **Wegovy**, used together with a reduced-calorie diet and more physical activity. The same active ingredient is also sold as **Ozempic**, but that is a separate product authorised for type 2 diabetes, not for weight management. Semaglutide has been authorised for use in the EU since 6 January 2022.
Active ingredient: **semaglutide**. Dosage range: **0.25 – 2.4 mg / week**.
## How it works
Semaglutide is a close copy of GLP-1, a hormone your gut releases after you eat. It shares about 94% of the structure of the natural hormone, so it fits the same docking points on cells, but it is built to last much longer in the body. Once attached to those docking points, it signals the parts of the brain that control hunger, including the hypothalamus and brainstem — in clinical studies people reported feeling full sooner, staying full for longer, feeling less hungry, and having fewer and weaker food cravings.
Because appetite falls, most people take in fewer calories without consciously trying, and that gap is what produces weight change over months. Semaglutide also slightly slows how fast the stomach empties early after a meal, and prompts insulin release only when blood sugar is high.
Lowest dose.
Step up gradually.
Maintenance dose.
Regular check-ins.
## What the studies reported
STEP 1 (*N Engl J Med* 2021;384(11):989-1002, ClinicalTrials.gov NCT03548935) is the pivotal trial behind the EMA's Wegovy assessment. Everyone in the trial also followed a reduced-calorie diet and increased physical activity, people with type 2 diabetes were excluded, and the study measured weight only up to week 68.
## What has been reported
Figures below are from the pooled STEP 1–4 phase 3 programme assessed by the EMA, semaglutide 2.4 mg versus placebo.
| Reaction | Semaglutide 2.4 mg | Placebo |
| ---------------------------------------------- | ---------------------- | ---------------------- |
| Nausea | 38.3% | 14.0% |
| Diarrhoea | 26.8% | 14.3% |
| Vomiting | 21.8% | 5.7% |
| Constipation | 21.8% | 10.2% |
| Gallbladder-related events (mainly gallstones) | 2.5% (1.6% gallstones) | 1.6% (1.1% gallstones) |
| Acute pancreatitis (independently confirmed) | 0.2% (4 people) | Under 0.1% (1 person) |
5.7% of people on semaglutide 2.4 mg stopped treatment because of side effects, versus 3.0% on placebo — mostly because of stomach and bowel symptoms.
## How Hi-Doctor handles it
It's prescribed alongside changes to diet and activity, as part of a medically supervised plan — a licensed EU doctor decides whether it's appropriate and safe for you. Our doctors review every weight-loss option and recommend what fits your history and goals. See the [Wegovy](/library/medicines/wegovy) page for the specific EU-authorised product and its injection and dosing guide, [how it works](/essentials/how-it-works) for the consultation process, and [pricing](/essentials/pricing) for the consultation fee.
## Start a consultation
Answer the weight-loss questionnaire and a registered doctor reviews it.
They decide whether treatment is appropriate, which one, and at what dose —
and declining is a normal outcome. See [what it costs](/essentials/pricing)
and [how the review works](/essentials/how-it-works).
This page is reference information, not medical advice and not a prescription.
Whether a medicine is appropriate for you is decided by a registered doctor
after reviewing your consultation.