I'm not sure whether you still need the answer but from my experience I can say that high glucose medium is not recommended. It strongly affects the cells metabolism. High glucose content would burst the growth of L929 cells - I once saw the effect of such medium on L929, they were still proliferating extremely fast even after a couple of passages with low glucose medium. Such fast growth is not a good thing because one should not alter the cells metabolism to conduct reliable assays.

As for the glutamine content, I also search for the information on how elevated amount of Glut (4mM instead of recommended 2mM) influences the L929 growth.

@paulina zietek Thank you for your answer :)

However, we need to clarify the final medium content for L929 cells: you need 4mM glutamine in total and 1g/l glucose. If you use standard DMEM with glutamine, it probably already contains 4mM of glutamine. If you uses MEM, it probably contains 2mM of glutamine and you have to add up to 4mM. There are also media without any glutamine addition, as well as with Glutamax (which is the analyl-glutamine dimer that ensures better glutamine stability). So, the medium formulation should always be checked before use :)

Personally, I would not recommend high glucose medium for L929, but actually I have just asked my friend and she frequently uses it for these cells. So I'm not sure what to say...