I want to learn
about clinical trials

I am looking for
a clinical trial

I’ve found a trial
I’m interested in

I am in a
clinical trial

I finished a
clinical trial

I want to learn about clinical trials

What is a clinical trial?

Clinical trials are a type of research. They involve people and test health-related “interventions” to see how they work.

Clinical trials often answer questions like:

  • Is the intervention safe?
  • Does the intervention improve or cure disease?
  • Does the intervention help people feel better?

In clinical trials, researchers are investigating the effects and side effects of a new or known treatment.

It can be new medicine, medical equipment and software programs, diagnostics and new treatment methods such as surgery or radiation therapy.

Clinical trials are a cornerstone of health research and knowledge from clinical trials is central to medical advances.

Pros and Cons
  • You can take part in testing the latest treatments.
  • You can improve the treatment options for yourself and others.
  • You can contribute to the development of new medicines and new forms of treatment.
  • You can have frequent and thorough contact with healthcare professionals.
  • You can get thorough knowledge about your own illness and how to best live with it.
  • You can get knowledge about your health that you otherwise would not have gained.
  • You can expect that participation is time consuming.
  • You may experience side effects, both known and unknown.
  • Your clinical trial doctor will inform you thoroughly about the clinical trial.
The four phases of a pharmaceutical trial

Clinical trials testing drugs are divided into four phases

Phase 1 – Is the medicine safe?
In phase 1, you examine how much of the medicine you can give before there are serious side effects. The experiments in phase 1 are often short with quite a few participants. The subjects are typically healthy volunteers. Only 1% of the total number of subjects are included in phase 1.

Phase 2 – Is the drug effective?
In phase 2, the relationship between dose and effect in people with disease is examined. Phase 2 typically involves between 50 and a few hundred participants. This type of trial usually lasts two to three months, but can last longer. 8% of the total number of subjects are included in phase 2.

Phase 3 – Does the drug work better than the treatment we know?
In phase 3, you look at the treatment effect and side effects in relation to the treatment you are already using. For example: Is the new treatment better, more effective or more gentle than the current one. Here you find out if the drug has the potential to be approved. Phase 3 trials typically involve between several hundred and several thousand participants. This type of experiment usually lasts several years. 81% of the total number of subjects are included in phase 3 trials.

Phase 4 – Are there side effects with long-term use, are there rare serious side effects?
Phase 4 trials are investigating side effects and effects in people who use the drug in their daily lives. There is a focus on rare side effects and on long-term effects and side effects. The studies in phase 4 run after the medicine has been approved. This type of experiment can have very different duration (months to years). 11% of the total number of subjects are included in phase 4 trials.

Who is responsible for clinical trials?

Scientific ethics medical committees
Before an experiment can begin, a scientific ethics medical committee assesses whether the experiment is ethically sound to carry out. They examine whether the trial participants rights have been respected, if the patient information is presented according to the current standards and whether the experiment will contribute new knowledge.

The Danish Medicines Agency
Before a trial may begin, the Danish Medicines Agency assesses whether the trial is medically justifiable to carry out. They look at both patient safety and whether the trial complies with current regulations.

The Sponsor
The overall responsible for the clinical trial, including the presence of adequate, effective arrangements to set up, run and report a research project.

The Investigator
Responsible for the conduct of the research, in particular adherence to the protocol at the research site.

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I have found a trial which I am interested in

Are you a match to the study?

Yes, if you as a participant fit all of the criteria for the clinical trial. Each clinical trial has its own criteria and you must fulfil all of them in order to enter the trial.

Inclusion criteria are requirements that you must meet in order to participate in that trial. For example:
Are you over 18 years old?
Do you have asthma?

There may also be physical requirements. For example:
Can you exhale more than 3 liters of air in one second?

Exclusion criteria are conditions that exclude you from being able to participate in the trial. For example:
Are you pregnant?
Are you a smoker?

Therefore, you must always have contact with the trial staff before you can count on participating in the trial.

What questions could I consider asking?

About the study:

  • What is the purpose of the study?
  • Why is this particular approach and design the most effective?
  • Who funds the study?
  • Have there been any comments to the study?
  • How long will the trial last?
  • What time do I need to invest in order to participate in the trial, and what are the trial investigations that are additional to my regular treatment?
  • Who will tell me about the results of the survey and how will I be informed?

About possible advantages and disadvantages:

  • What are the possible short- and long-term benefits for me?
  • What are the possible short- and long-term disadvantages for me?
  • Is the balance between pros and cons of this study more attractive to me than the other treatment options?
What are my rights as a participant?

It is ALWAYS voluntary to participate in a clinical trial. And you can withdraw from the clinical trial at any time. If you choose to stop as a participant, it does not affect your future treatment.

When participating in a clinical trial, you must have information about the experiment itself and about the pros and cons of participating in the specific study. You must have the information both orally and in writing. You are covered by the Patient Compensation, both when you participate in a clinical trial and if you choose not to take part.

For those who, permanently or temporarily, are unable to make an informed decision whether to consent to participate or not, the immediate family or guardian can give consent. For children under the age of 15, parents or guardians must give consent.

Personal data is an important part of clinical trials. Therefore, you must decide whether your health data may be processed and exchanged between those who perform the clinical trial before you can participate. In order to participate in the trial you must allow sharing your data collected in the trial.


What are some possible benefits and risks?

If you are being treated with experimental medication or procedures, it may prove to be better for you than the treatment you would otherwise have received. It may also turn out that it is not better.

For additional information, see Pros and Cons.

If you or your trial doctor assess that the trial medication or procedure is not beneficial to you, then treatment should be stopped immediately.

As a participant in a clinical trial, you will often have more contact with doctors and nurses. The increased attention to you as a patient is perceived as an advantage to some and as a disadvantage to others. Only you can decide whether you see this is good or bad for you.

Will I get paid?

As a rule of thumb, you will not be paid to participate in a clinical trial. This is because it should always be voluntary to participate in a clinical trial. 

You will often get reimbursed for transportation costs.

Where does the trial take place?

The clinical trial typically takes place at a hospital, sometimes university hospital, or clinic. Here you will meet doctors and nurses who are employed at the hospital and who also work with clinical trials.

If you are part of a clinical trial, you will meet with a trial physician. The doctor is a specialist in the disease and the treatment to be investigated. The attending physician assumes responsibility for your treatment during the period in which you are participating in the trial.

I am in a clinical trial

General information

You can share your participation in a clinical trial and information about it with anyone you wish.

You should have a copy of the patient information and informed consent from the clinical trial that describes the clinical trial in detail.

It is important to share information with your health care providers about any medication you may be on for the clinical trial. Consider bringing the Patient Information folder.

Who do I contact if I have questions or concerns about the clinical trial?

You should contact your trial doctor.

Please refer to your patient information. 

Can I leave the clinical trial at any time?

Yes – absolutely. It is one of your central rights as a clinical trial participant.

If you decide to leave, please consider taking the time to explain your decision to the trial doctor.

I finished participation in a clinical trial

How can I find out the results from the clinical trial?

As a clinical trial participant, you should be informed of the results of the clinical trial once the entire trial is complete. You should speak to your trial doctor or trial team about how to obtain this information once the whole trial is completed. The whole trial may be completed a long time after your participation completed.

What happens to my treatment now that I have finished my participation in the clinical trial?

When you have completed your clinical trial participation, you will most often stop the treatment you received in the trial. When you are a patient, you will in many cases resume the treatment you received before the trial. There are however some clinical trials in which the treatment which is studied can continue after the trial is completed.

Podcast on Clinical trials

What is Clinical research?
  • Henriette Svarre Nielsen, Professor of Reproduction and womens diseases. 
  • Ulrik Lassen, Professor of Clinical Oncology and Personalised Medicine.
Private or Public research?
  • Leif Vestergaard Pedersen, who is former director of the Danish Cancer Society, a member of the Danish Medicines Agency and i.a. former health director in the Central Jutland Region.
  • Jakob Wedsted, postdoc at the Center for Advanced Studies in Biomedical Innovation Law
How are medicines tested to actually work?
  • Anne-Marie Axø Gerdes, Chairman of the Council on Ethics
  • Steffen Thirstrup, advisor at NDA Advisory Services and former head of the drug approval in the Danish Medicines Agency
What does big data and artificial intelligence mean for future clinical research?

Ismail Gögenur, Professor at the Center for Surgical Science at Sjællands Universitetshospital

Nikolai Brun, then head of the medical evaluation and biostatistics unit at the Danish Medicines Agency – and then chairman of the big data task force at the European Medicines Agency, EMA

How will the conditions for clinical research become even better?
  • Ida Sofie Jensen, CEO, Lif
  • Allan Flyvbjerg, Center director of Steno Diabetes Center