Semaglutide, tirzepatide, liraglutide: GLP-1 medicines at a glance
Three active substances, one shared principle and a few important differences: how often they're used, where they act and what applies when switching.
- GLP-1
- active substances
- basics
In short
Semaglutide, tirzepatide and liraglutide all mimic the gut hormone GLP-1. Tirzepatide also acts on the GIP receptor. The biggest everyday difference: liraglutide is injected daily, the other two once a week.
Which one suits you can't be read off a table. It depends on your medical history, tolerability and availability, and it is a medical decision.
What all three have in common
GLP-1 is a hormone the gut releases after eating. It signals fullness to the brain, slows stomach emptying and is involved in regulating blood sugar. These medicines mimic that signal but last much longer than the body's own hormone.
All three are prescription-only. For weight management they are approved for adults with a BMI of 30 or more, or 27 or more with at least one weight-related condition, alongside diet and exercise. And all three are increased slowly, because the gut is sensitive at first.
The differences at a glance
| Attribute | Semaglutide | Tirzepatide | Liraglutide |
|---|---|---|---|
| Target | GLP-1 receptor | GIP and GLP-1 receptors | GLP-1 receptor |
| How it's used | Injection once a week; also approved as a daily tablet for weight management | Injection once a week | Injection once a day |
| Starting | Gradual titration over several weeks | Gradual titration over several weeks | Gradual titration, usually in weekly steps |
| Common side effects | Mainly gastrointestinal | Mainly gastrointestinal | Mainly gastrointestinal |
What the second target means
GIP is another gut hormone released after eating. Tirzepatide activates both receptors, GIP and GLP-1, which is why it is described as having a dual mechanism.
Whether that makes a difference for you is an individual question. The mechanism alone says nothing about how well someone tolerates a medicine or how they respond to it.
What studies show, and what they don't
All three have large study programmes in weight management: SCALE for liraglutide, STEP for semaglutide and SURMOUNT for tirzepatide. SURMOUNT-5 was the first head-to-head comparison of tirzepatide and semaglutide in people with obesity without diabetes.
SURPASS-2 is also often quoted. That study compared tirzepatide with semaglutide 1 mg in people with type 2 diabetes, so its results can't simply be transferred to weight management without diabetes.
Studies give averages under controlled conditions. How things go for you depends on many factors, including tolerability, dose, medical history and daily life.
Can you switch between them?
In principle yes, but only on medical instruction. Reasons can include poor tolerability, supply shortages or wanting a different dosing rhythm.
There is no universal washout rule for switching. When the new medicine starts and at what dose is decided by the prescribing doctor. One thing is fixed: two GLP-1 medicines are not used at the same time. Whether and when a switch is possible is decided by the medical review in each individual case.
What about costs?
Prices differ by active substance, dose and pack size. For weight management, German statutory health insurers generally do not reimburse these medicines. At Solean, treatment is self-pay only; nothing is billed to statutory or private insurance.
What applies to every GLP-1 treatment
- Don't increase, double or abruptly stop a dose on your own
- Tell the surgical and anaesthesia team before surgery or anaesthesia, because the stomach empties more slowly
- Not for use in pregnancy or breastfeeding. If you want to become pregnant, clarify this with a doctor beforehand.
- Seek medical help immediately for severe, persistent abdominal pain that may spread to the back
Frequently asked questions
Note
This Journal article offers general information. It is not a diagnosis, a prescription or a promise of any result. Whether treatment is suitable for you is decided by a doctor after reviewing your questionnaire. For acute or severe symptoms, contact your GP, the out-of-hours medical service (116117) or, in an emergency, 112. Whether and how a switch or a dose change happens is decided by the doctor in each individual case.
Sources and medical review
Based on European Medicines Agency product information and the studies listed. Educational only; does not replace an individual medical decision.
- European Medicines Agency product information for semaglutide, tirzepatide and liraglutide
- Pi-Sunyer X et al. A Randomized, Controlled Trial of 3.0 mg of Liraglutide in Weight Management (SCALE). N Engl J Med 2015
- Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med 2021
- Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med 2022
- Aronne LJ et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5). N Engl J Med 2025
- Frías JP et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). N Engl J Med 2021