The diagnosis of childhood-onset growth hormone (GH) deficiency (GHD) is not straightforward, requiring a comprehensive clinical, anthropometric, biochemical, endocrine, and neuroradiological assessment. Although pharmacological GH stimulation tests are still considered the gold standard for GHD diagnosis, they are burdened by both poor specificity and side effects. The measurement of insulin-like growth factor I (IGF-I), due to its close GH dependency, was proposed for diagnosing GHD. However, a number of factors may affect the measurements. Herein, we propose an algorithm based on both IGF-I determination and anthropometry, aimed at simplifying the diagnosis of GHD in prepubertal children.