Cell lysis, a process that releases host oligonucleotides, is required in many biotechnological applications. However, intact oligonucleotides in crude cellular lysates increase the viscosity of lysates, which complicates downstream processes and routine laboratory workflows. To address this, nucleases that hydrolyze the intact oligonucleotides are commonly added, either as purified enzymes or co-expressed in genetically engineered bacterial strains. To measure oligonucleotide hydrolysis, common DNA quantification methods, such as qPCR or fluorescence-based, require expensive reagents and equipment, and cannot distinguish different-sized DNA fragments. Here, we outline a simple alternative method for measuring DNA/RNA hydrolysis in cellular lysates, by measuring their viscosity. This method only requires common laboratory supplies and a cell phone camera.