Summary: We developed a scalable, label-free all-electronic sensor for D-glucose based on a carbon nanotube transistor functionalized with pyrene-1-boronic acid. This sensor responds to glucose in the range 1 μM–100 mM, which includes typical glucose concentrations in human blood and saliva. Control experiments establish that functionalization with the boronic acid provides high sensitivity and selectivity for glucose. The devices show better sensitivity than commercial blood glucose meters and could represent a general strategy to bloodless glucose monitoring by detecting low concentrations of glucose in saliva.