A 46-year-old man presents at the outpatient clinic with elevated serum liver tests observed since two years. Serum ALT, AST, and gamma-glutamyl transferase are mildly elevated whereas bilirubin and alkaline phosphatase are within the normal range. Hemoglobin and reticulocytes, leucocytes and platelets are within the normal range. Abdominal ultrasound reveals no relevant abnormalities. Transient elastography (6.3 kPA, IQR 1.3, success rate 100%) is within the normal range. Serum ferritin is 820 μg/L and transferrin saturation is 87%. HFE genotyping reveals homozygosity for pC282Y. Additional risk factors for liver cancer such as alcohol consumption, type 2 diabetes mellitus, and viral hepatitis have been excluded.

What is the first therapeutic step?