I don't know if the company is GMP certified. I do know that their product works well. I tried some stuff from Alibabi out of curiosity as it was a quarter of the price and I didn't notice it working at all. With BrainVitaminz, you notice the effect within about half an hour of a dose. In my case, mildly improved cognition and memory plus a bit of help with negative symptoms. I swear by it and keep pouches of it at home, at work, and a spare in my car so I won't run out. It really does work.
I have trouble remembering personal hygiene despite being high-functioning. I find I'm better with remembering personal hygiene when on sarcosine. Probably 25% better. I'm also much better at mentally stacking multiple tasks (I can have up to 25 files open at a time at work). Take away my sarcosine and my mental stacking ability really suffers.
I can't tell you about glutamate levels as I'm neither a doctor or researcher. I can tell you that none of my doctors have expressed concern about it and they approve of my using it based on my reported results. In fact, my main psychiatrist (I'm currently seeing three) is recommending it to his other patients with SZ.