I have United Health Care by the way, they payed for the test this and last time I was pregnant
My OB does a blood test that tests for a variety of things and one of the tests is the gender, you have to be 10+ weeks for that. My insurance pays for it.
You can pay about 100$ for sneak peak a blood gender test at 9 weeks you can do 3D/4D ultrasound at 14 or 15 weeks. If you don't want to pay out of pocket you can wait till your 20 week anatomy scan with your Dr.
Now by blood at any point of pregnancy but test is expensive. Usually at the 20 week anatomy scan, but I have heard women finding out a few weeks before then