Side effects & safety

Is it dangerous?

Registered GLP-1 weight-loss medications are considered acceptably safe when used under medical supervision for approved indications. Like any medicine, they have side effects and there are situations in which they are not suitable. The biggest real danger lies not in the registered medicines themselves, but in counterfeit products bought without a prescription. This medication is prescription-only: a doctor assesses whether it is suitable for you and supplies it through the pharmacy. This is general information and not medical advice.

Safety under medical supervision

GLP-1 medications such as semaglutide and tirzepatide have been assessed and registered by medicines authorities (such as the European Medicines Agency, EMA). For the approved indications, the benefits outweigh the risks, provided they are used under the guidance of a doctor.

The doctor looks at your situation, any other conditions and medications, and supervises the build-up and check-ups. Most side effects are gastrointestinal complaints; serious side effects are rare. Read more about the side effects of Ozempic and of Mounjaro.

When is it not suitable?

There are situations in which a doctor will not prescribe this medication, or only with caution. The patient leaflet and the doctor address this for each individual. Examples of points of attention mentioned in product information:

Pregnancy and breastfeeding: use during pregnancy is not advised because there is insufficient experience.
Family history of certain thyroid cancer (medullary thyroid carcinoma) or MEN 2 syndrome, depending on the specific product.
Previous inflammation of the pancreas or certain gastrointestinal conditions.

Whether a medicine is suitable is always assessed by your doctor. Consult the patient leaflet for your specific product for the complete contraindications and warnings.

The biggest real danger: counterfeits

The biggest risk arises when people buy GLP-1 medication without a prescription, for example via dubious websites. These products may be counterfeit: a wrong or unknown dose, contaminants, or an entirely different substance. Without a doctor and a pharmacy, there is no control over quality, dosing or suitability.

Never buy GLP-1 medication without a prescription. Read how to tell reliable products from suspicious ones on recognising counterfeits.

Safe use and reporting side effects

You limit the risks by using the medication only on prescription, following your doctor's titration schedule, not adjusting the dose yourself, and contacting your doctor at any warning sign.

You can report suspected side effects to the Netherlands Pharmacovigilance Centre Lareb via www.lareb.nl. For a complete overview, consult the patient leaflet.

Frequently asked questions

Are weight-loss medications safe?

Registered GLP-1 medicines are acceptably safe under medical supervision and for approved indications. Like any medicine, they have side effects; your doctor assesses whether one is suitable for you.

What is the biggest risk with GLP-1 medication?

The biggest real danger is counterfeits bought without a prescription. Without a doctor and a pharmacy, there is no control over dosing, quality or suitability. So never buy these medicines without a prescription.

When am I not allowed to use GLP-1 medication?

Among other things, use during pregnancy is not advised, and certain family histories or conditions call for caution. Your doctor assesses this and the patient leaflet gives the details.

Is Ozempic or Mounjaro dangerous for the heart?

This depends on your personal situation. Discuss any existing heart or other conditions with your doctor, who assesses whether the medicine is suitable. Also consult the patient leaflet.

Official sources on this topic

Independent, authoritative information from official bodies: