One of the main topics currently, both in medicine and sports applications, is the determination of lactate concentration in blood and sweat.This paper focuses on the development of an electrochemical biosensor for lactate, in which the testing of one potential design was conducted on two electrodes: a 3D glassy carbon disk electrode (GCE) and a screen-printed carbon electrode (ED-S1PE-C2, Micrux Fluidic). Both electrodes were coated with layers: a Prussian blue layer as an electrocatalyst for hydrogen peroxide reduction, lactate oxidase as a catalyst for the oxidation reaction of lactate, and a chitosan layer whose role was to securely retain the enzyme layer on the electrode surface. The response of individual layers on the electrodes, as well as the response of the final, fully coated electrode with all layers, was examined using cyclic voltammetry and chronoamperometry methods. The fully coated GC electrode did not provide a meaningful response to lactate. Due to the absence of chitosan modification with 1 M NaOH and consequently poor adhesion, the layer slid off the electrode during the first immersion. The fully coated screen-printed carbon electrode with the modified chitosan layer did not, in any case, provide a meaningful response in relation to the change in lactate concentration during cyclic voltammetry recordings. The chronoamperometric response showed a successful response to lactate in the concentration range of 17 mM to 41 mM. The obtained response showed very poor linearity (R2 = 0,7706) and poor sensitivity (-0,0572 μA/mM), indicating that the current value does not significantly change with the change in lactate concentration.