At the point of care (POC), on-side clinical testing allows fast biomarkers determination even in resource-limited environments. Current POC systems rely on tests selective to a single analyte or complex multiplexed systems with important portability and performance limitations. Hence, there is a need for handheld POC devices enabling the detection of multiple analytes with accuracy and simplicity. Here we present a reconfigurable smartphone-interfaced electrochemical Lab-on-a-Chip (LoC) with two working electrodes for dual analyte determination enabling biomarkers' selection in situ and on-demand. Biomarkers selection was achieved by the use of electrodepositable alginate hydrogels. Alginate membranes containing either glucose oxidase (GOx) or lactate oxidase (LOx) were selectively electrodeposited on the surface of each working electrode in around 4 min, completing sample measurement in less than 1 min. Glucose and lactate determination was performed simultaneously and without cross-talk in buffer, fetal bovine serum (FBS) and whole blood samples, the latter being possible by the size-exclusion filtration capacity of the hydrogels. At optimal conditions, glucose and lactate were determined in a wide linear range (0-12 mM and 0-5 mM, respectively) and with high sensitivities (0.24 and 0.54 μA cm-2 mM-1, respectively), which allowed monitoring of Type-1 diabetic patients with a simple dual analysis system. After the measurement, membranes were removed by disaggregation with the calcium-chelator phosphate buffer. At this point, new membranes could be electrodeposited, this time being selective to the same or another analyte. This conferred the system with on-demand biomarkers' selection capacity. The versatility and flexibility of the current architecture is expected to impact in POC analysis in applications ranging from homecare to sanitary emergencies.