AbstractGuanidinoacetic acid (GAA, also known as glycocyamine or guanidinoacetate) is a naturally occurring alpha amino acid derivative and newly recognized dietary compound obtainable by different foods and nutritional supplements. Anecdotal evidence suggests that the GAA exposure from supplements might be a major source of GAA supply, out‐competing other food sources for several orders of magnitude. This original technical paper summarizes information about GAA levels in different nutritional supplements, as derived from the U.S. National Institutes of Health dietary supplement database.