Abstract Human telomere length is tightly regulated and associated with diseases at either extreme. but how these bounds are established remains incompletely understood. Here. we developed a rapid cell-based telomere synthesis assay and found that nucleoside salvage bidirectionally constrains human telomere length. https://www.nacrack.com/hot-savings-HiBoost-Home-15K-Smart-Link-F20G-5S-IoT-limited-super/