You might. A small number of states still require a reason (excuse). You will have to affirm that you cannot vote in person for physical reasons such as age, disability or being physically absent from your state that day.
You can check the Voting Methods and Options chart to see if your state offers Absentee Voting with or without an "Excuse", by which they mean, a reason. Make sure to click any help bubbles for further information.
If an excuse is required, go to the State Voting Requirements directory, choose your state, and click into the General Information section. Scroll down to the section on absentee voting to see the list of reasons.
To generate a vote-by-mail ballot request, go to Register to Vote/Request Your Ballot. The list of allowable excuses is integrated into the form generation process. At the end of it, you will download, print, sign and send in your form to your election office according to the instructions that print with the form.
Note: If you are out of the country or in the military, you can also vote absentee by mail. All options will be presented to you when you go to Register to Vote/Request Your Ballot.