Background: Protein supplements are one of the most frequently dietary supplements used by athletes and non-athletes in Saudi Arabia. Objective: To assess the knowledge, attitude and practice of Saudi population toward the protein supplements, examine the relationships of practice with education level, effect of protein on kidneys and lipid profile, assess the types and source of protein supplements, assess the correct use of protein supplements according to exercise intensity and determine protein content and heavy metals in protein supplements. Methods: A national cross-sectional survey was conducted during October-December 2017 on protein supplements users in Saudi Arabia. Moreover, samples of the best selling protein supplements were analyzed to determined total protein and heavy metals content. Results: A total of 398 filled protein supplements user questionnaire. The wrong practice of use associated with the effect of protein supplements on renal function and lipid profile.The percentage of protein content in isolated whey protein (68.18%) whiles by Kjeldhl analysis (80.55%). Concentrated whey protein contain (72%) and by kjeldhl analysis (77.2%). Hydrolyzed collagen containing (100%) protein and by kjeldhl analysis (91.25%).The amount of heavy metals in isolated whey protein contains arsenic (83 μg/kg), mercury (<10 μg/kg) and lead (18 μg/kg), while hydrolyzed collagen sample contains arsenic (101 μg/kg), mercury (<10 μg/kg) and lead (49 μg/kg). Conclusion: The current study reveals an evidence for lacking of the awareness, negative attitude and abuse of protein supplements, demonstrates necessity to further education regarding the use and purchasing of protein supplements to ensure the quality of these products.