What are normal results for glycine in cerebrospinal fluid?

Difficult question: Glycine is an Amino Acid that is the product of normal protein metabolism. Rare cases of inborn errors of metabolism result in a defect in metabolism of certain Amino Acids including glycine. A very rare disorder is non-ketotic hyperglycinemia where the glycine in the CSF is many times normal. The range of normal varies with ingestion of protein and depending on the form of laboratory assay.