Your employer must keep your health insurance and other benefits in place for at least the first 30 days of active military service when you are ordered to federal or state active duty other than active duty for training. After the first 30 days your employer must offer you the option of continuing those benefits at your own expense.
Give your employer a copy of your orders before you leave and ask them to continue your benefits. Tell them in writing if you want to keep paying for coverage past the first 30 days.
Your orders to federal or state active duty, and your current benefit enrollment paperwork.
