Taking 200 micrograms of selenium every day for about 6 months helps men with certain types of infertility have better sperm quality, including more sperm, better movement, and better shape.

Taking both selenium and N-acetyl-cysteine together for 6 months works better for improving sperm quality than taking either one alone for men with certain types of infertility.

The benefits of selenium and N-acetyl-cysteine on sperm quality for men with certain types of infertility only last while they're taking the supplements, and may go away after stopping.

Taking selenium or N-acetyl-cysteine for 6 months doesn't have enough data to know if it's safe long-term for men with certain types of infertility.

Taking selenium or N-acetyl-cysteine for 6 months doesn't seem to help men with certain types of infertility have babies, even though it improves sperm quality.

This study doesn't show that selenium or N-acetyl-cysteine helps men with infertility from other causes have better sperm quality or fertility.