TetraSOD® is a unique marine phytoplankton (Tetraselmis chuii) SOD-rich ingredient that is grown under patent-protected technology exclusively designed by the company Fitoplancton Marino, S.L. (Spain). In a previous pilot trial, the ability of TetraSOD® (dose: 250 mg/day) to improve semen characteristics in idiopathic infertile men after three months of treatment was assessed, revealing significant improvements in almost all of the analyzed parameters. In a further clinical trial close to finish (ClinicalTrials.gov Identifier: NCT04864314) using the same dose, such positive results have been tested again in a higher number of patients, and additional parameters have been included in order to gain insights into the sperm physiological changes that underpin the improvement in semen quality. In this new clinical trial, an intermediate dose (125 mg/day) is going to be tested in an attempt to determine a range of TetraSOD® dosage being clinically active for the treatment of male infertility.