The process for changing one’s name and/or gender on a driver’s license or state identification varies from state to state.
In California, name change does not require a doctor's letter. As of January 1, 2019, California will no longer require a doctor's letter for gender marker change on a driver's license either.
For a gender marker change in other states, most require that a health care provider fill out a form and/or write a letter, but different language is required for different states. They will require the originals of the form and/or letter. To learn about the requirements in your state, visit the National Center for Transgender Equality’s Interactive Map.