Human NAD+ levels are detected using a semi-synthetic NAD+ biosensor, requiring only 5 milliliters of fingertip blood. This biosensor is suitable for various biological samples like blood, saliva, and cell lysate. Its detection sensitivity is comparable to LC-MS, the gold standard for NAD+ concentration detection, but offers more convenient sample preparation, quicker detection, and lower cost. The NAD+ biosensor can be integrated into either a tabletop or a portable device, and its research has been published in notable journals like Science and Nature Metabolism