How clinical trials are done

Trials that look at treatments usually take place in four stages, called phases. If a phase is successful, the trial moves onto the next phase.

Phase 1 trials test how safe a new treatment is.

Phase 2 trials look at how effective a treatment is.

The new treatment is given to a larger group of people with a particular disease, to see how effective the treatment is.

Phase 3 trials compare the new treatment with the existing treatment.  

Phase 4 trials are carried out after a drug has been licensed. Further information is collected on long term risks and benefits.

Quality of life studies: Most well planned trials include a quality of life study.

Researchers may look at the impact treatment has on you, considering  like how often you have to travel to the hospital.