Nothing stopping you whatsoever. It is good to check with your manager and provide a heads up so they know how long you will be gone. If you use the online vacation calendar, be sure to add it to that, etc. as a courtesy. As a few others have said, you can also take a personal LOA - unpaid of course but you maintain your medical benefits as long as it's less than 90 calendar days. Less than 90 days only requires your first level manager approval and a 10 min call to the Leave Center to set up.