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Here, we propose a microfluidic paper-based analytical device (mu PAD) implemented with a near-field communication (NFC) tag as a portable, simple and fast colorimetric method for glutathione (GSH) determination. The proposed method was based on the fact that Ag+ could oxidize 3,3';,5,5'-tetramethylbenzidine (TMB) into oxidized blue TMB. Thus, the presence of GSH could cause the reduction of oxidized TMB, which resulted in a blue color fading. Based on this finding, we developed a method for the colorimetric determination of GSH using a smartphone. A mu PAD implemented with the NFC tag allowed the harvesting of energy from a smartphone to activate the LED that allows the capture of a photograph of the mu PAD by the smartphone. The integration between electronic interfaces into the hardware of digital image capture served as a means for quantitation. Importantly, this new method shows a low detection limit of 1.0 mu M. Therefore, the most important features of this non-enzymatic method are high sensitivity and a simple, fast, portable and low-cost determination of GSH in just 20 min using a colorimetric signal., BBVA Foundation, European Commission European Commission Joint Research Centre H2020-MSCA-IF-2017-794885-SELFSEN, Spanish Government PID2019-103938RB-I00 PID2020-117344RBI00, Junta de Andalucia BFQM-243-UGR18 P18-RT-2961, European Commission