Organic electrochemical transistors are emerging as prominent biochemical sensors for multi-sensing, including ions, metabolites, hormones, or viruses. However, the implementation of the devices is mainly limited to a single-analyte detection and a single-shot measurement in a non-integrated, rigid configuration. In this work, optimized technology and integration processes enable fully-integrated inkjetprinted OECT platforms on flexible substrates for real-time multi-ion sensing. The combination of miniaturized OECTs with and without ionselective membranes; and the use of portable read-out electronics for reading multiple OECT sensors allow the discrimination of different cations in sweat. The devices show high sensitivities of ~20 %/dec of concentration of sodium and potassium ions during the calibration in the respective sweat concentration ranges. The platforms are demonstrated to quantify ions in real human sweat samples effectively, with correlated values to commercial ion sensors. The use of the developed integrated devices with a wearable microfluidic system could enable the real-time monitoring of the hydration status of individuals.