Is it true that you would test for high glycine in urine if your receptors were not sensitive to it and using it and low if receptors were reacting to it properly. The same applied for some other animo acids.
What the body cannot utilize will end up being excreted pretty quick.
It said the neurotransmitter receptors were not reacting to the glycine as well in some people causing anxiety. So does that mean even if you took more glycine it would not help in that case?
Correct. But I never heard of this being a cause of anxiety and I doubt if this would be the case since there are other neurotransmitter inhibitors the body can utilize other than glycine.