Semen viscosity is an important parameter in the assessment of ejaculate quality, affecting the motility of sperm and their ability to penetrate female reproductive secretions, which is crucial for fertilization. Increased ejaculate viscosity is more common in men with fertility issues and is associated with poorer in vitro fertilization outcomes and reduced embryo transfer efficacy. Viscosity assessment is performed following semen liquefaction, a process that occurs post-ejaculation due to the proteolysis of seminogelin by kallikrein-3, regulated by zinc ions. Elevated semen viscosity may be associated with various disorders, including dysfunction of the male accessory glands, infections and inflammations of the urogenital tract, oxidative stress, dehydration, cystic fibrosis, and the presence of sperm antibodies. Excessive semen viscosity can lead to fertility issues by impairing sperm function and potentially causing DNA damage.