S Acetyl L Glutathione, 100 mg, 120 Veggie Capsules Glutathione IV Therapy: Timeline for Skin Lightening How long does glutathione injection take to whiten skin? 1 to 2 skin whitening injection can be injected in a week, so the complete treatment may take up to 3 months. As Our SAG plus 300 supplement is an oral method to increase glutathione levels in the body and protect our cells from damage1. The innovative formulation contains a premium high dosage S acetyl glutathione