Frequently Asked Questions About the GRE
If you go back and take the GRE again after already taking it once, but haven't put in an extended effort at test preparation, then your score may go up or down a few points.
By no means does taking it again guarantee you a higher score.
It's easy to look at your first score as a lower bound, but remember that you might have got lucky.
Maybe the next time you'll find it more difficult, or you'll be more tired, or you won't enjoy the reading passages as much.
Among people who retake the test, there is a tendency to improve slightly, but a sizable fraction of people actually get a lower score.
However, if you know that something went wrong the first time, and if you know you can be in a better position to retake the test, then by all means go for it.
But unless there's reason to think you'll be better off the next time you take the test, why make the gamble?
Unless, of course, you've done some test prep....