Can I choose which group I'm in during a clinical trial?

No. In a clinical trial that uses randomization, neither you nor your doctor gets to choose which group you're placed in. Assignment happens by chance, usually decided by a computer program.

This is intentional. Randomization exists to prevent bias — a situation where study results are shaped by human choices rather than by the treatment being tested. If doctors could choose group assignments themselves, they might, even unintentionally, place patients who seem healthier into the group getting the new treatment, which could make that treatment look better than it actually is.

Even though you can't choose your group, you still have important protections. Before joining a randomized trial, you'll go through informed consent, where the research team explains that the trial uses randomization and what each group would receive. If you have concerns about not being able to choose, that's a good topic to raise with the study team before deciding whether to join.