Used in research as a metabolic intermediate and analog of creatine, 5-guanidinopentanoic acid helps study creatine transport and metabolism in cellular systems. It is employed to investigate conditions related to energy metabolism disorders, particularly in muscle and nerve tissues. Due to its structural similarity to creatine, it may act as a substrate or inhibitor in enzyme assays involving creatine kinases or the creatine transporter. It is also explored for potential use in developing diagnostic tools or therapies targeting metabolic diseases.