IV rehydration was formerly a common technique for athletes. The World Anti-Doping Agency prohibits intravenous injection of more than 100mL per 12 hours, except under a medical exemption. The United States Anti-Doping Agency notes that, as well as the dangers inherent in IV therapy, "IVs can be used to change blood test results (such as hematocrit where EPO or blood doping is being used), mask urine test results (by dilution) or by administering prohibited substances in a way that will more quickly be cleared from the body in order to beat an anti-doping test". Players suspended after attending "boutique IV clinics" which offer this sort of treatment include footballer Samir Nasri in 2017 and swimmer Ryan Lochte in 2018.