Phenibut (β − phenyl − γ−aminobutyric acid) is licensed for use as a medicine in countries outside of the European Union (EU), but has also been sold as a “food supplement” from online shops to the general public in the EU. We present a case of phenibut use in a 25-year-old female undergoing alcohol and drug addiction treatment. She reported using phenibut, which she had purchased readily over the internet as a “food supplement.” Our clinical laboratory located in a hospital in the same region received urine samples for analysis which confirmed ingestion of phenibut. Identifying and responding to new psychoactive substances (NPS) emerging on the drug markets poses a challenge to clinical and forensic drug testing. A comprehensive laboratory analysis approach can identify the use of multiple NPS, including those used as medicines, offering beneficial opportunities for drug treatment services and clinical laboratories to work together.