Uptake measures need radiolabelled compounds.

You may indirectly test what is the CO2 production or any metabolic rate by varying Glu concentration. 

There are fluorescent kits available for cultured cells. If you have access to whole body scanning (e.g, using a LiCor Odyssey) you may be able to use that type of chemistry in vivo. Worth looking into, anyway.

There are colorimetric and fluorometric methods available, I linked a couple.

http://www.abcam.com/glucose-uptake-assay-kit-colorimetric-ab136955.html

http://www.abcam.com/glucose-uptake-assay-kit-fluorometric-ab136956.html

I guess i´ll stick with radioactivity. 

Thanks a lot for your time and info.