Several techniques are currently employed to assess average telomere length in eukaryotic cells. One method is the Terminal Restriction Fragment (TRF) southern blot. There is a Web-based Analyser of the Length of Telomeres ([https://www.ceitec.eu/chromatin-molecular-complexes/rg51/tab?tabId=125 WALTER]), software processing the TRF pictures. A Real-Time PCR assay for telomere length involves determining the Telomere-to-Single Copy Gene (T/S) ratio, which is demonstrated to be proportional to the average telomere length in a cell.
Tools have also been developed to estimate the length of telomere from whole genome sequencing (WGS) experiments. Amongst these are TelSeq, Telomerecat and telomereHunter. Length estimation from WGS typically works by differentiating telomere sequencing reads and then inferring the length of telomere that produced that number of reads. These methods have been shown to correlate with preexisting methods of estimation such as PCR and TRF. Flow-FISH is used to quantify the length of telomeres in human white blood cells. A semi-automated method for measuring the average length of telomeres with Flow FISH was published in Nature Protocols in 2006.
While multiple companies offer telomere length measurement services, the utility of these measurements for widespread clinical or personal use has been questioned. Nobel Prize winner Elizabeth Blackburn, who was co-founder of one company, promoted the clinical utility of telomere length measures.