2-5g is an absolute placebo amount when it comes to glutamine.
glutamine is mainly absorbed by the intestines, and the good thing about glutamine is, when your intestines are fed on glutamine from supplementation, they don't feast on other amino acids coming along.

talk about 10g 3 times a day, then we have a proper glutamine supplementation. worthless in my opinion though.
nice if you have the money or a cheap glutamine source, otherwise drop it.
I have both, money and a cheap source, yet i find it useless.
be sure to have protein, amino acids, BCAA, creatine, then think about glutamine.
i would have some ZMA, green tea extract or the likes when it comes to boosting the immune system.