No idea what model you have? I looked a couple of models up online and for instance the MSI model does not say if if supports uefi or not.
I have a Saphire R9380x that I know supports UEFI. However the name on the box includes UEFI in the product name. It may be that there were 2 flavors of cards made. I know that some cards had a physical switch to UEFI also.
You should probably look at your owners manual and if that does not help, contact the support department of you cards maker.