Side effects of medicines

Updated 12 March 2024

Most people will need to take medication at some point in time either to prevent, alleviate or treat a condition – or because it is vital. It is therefore crucial that the medicine we take works as intended and has the fewest possible side effects.

The Danish Medicines Agency monitors the safety of all medicines authorised and sold on the Danish market. When we monitor the safety of a medicine, we weigh the medicine’s effect against its side effects. We can accept more serious side effects for medicines used to treat serious diseases such as cancer, but we only accept mild side effects for medicines for less serious conditions.

Report side effects to medicines

Anyone can report side effects to the Danish Medicines Agency, but doctors, dentists and midwives have a special obligation to do so. Only a suspicion is needed to report.

When a new medicine is authorised and becomes available, it has been tested in a defined and well-controlled group of trial subjects. As a result, we know how the medicine works and what the most common side effects are. These side effects are described in the medicine’s package leaflet. Once a medicine has been authorised and many patients start using it, side effects that we didn’t see earlier could show up now. It is important for patient safety that the Danish Medicines Agency is informed of these side effects, and your report is very important in this respect.

Report side effects to medicines to humans (in Danish only)

Learn about the side effects of a medicine

The medicine’s package leaflet

A package leaflet is supplied with all medicine, and it is written for the medicine user. It gives information about the medicine’s known side effects and tells you how the medicine works and how to take it.

You can also find the package leaflets of medicines on the Danish market at www.indlæ (click ‘English version’ at the top). The package leaflets are in Danish only.

The medicine’s summary of product characteristics (SPC)

The summary of product characteristics (SPC) is written for healthcare professionals. It is a very detailed description of the medicine’s properties and the conditions for use.

You can search for SPCs for medicines on the Danish market at The SPCs are in Danish only. 

All medicines have side effects

All medicines have side effects, but they are mild and transient for most medicines.

Side effects are unwanted effects of a medicine. They can range from anything from nausea, headache or a rash to fatal side effects in the worst-case scenario.

People react differently to medicine. Some have side effects, others don’t.