Just refill it again..... there is really no way of checking the level..... better yet, drain and refill it.

Reason I emphasize this, it's because I was on the verge of taking a tranny out to replace the clutch due to a customer complaint similar to yours. As I get ready to make preparations to do so.... as I attempt to drain the tranny prior to taking it out.... only a few drops came out. I added oil and problem solved. However, the owner had already lost money for a tow service and new clutch kit... that cost him well over $500... the car was towed from NC to Va Beach.