We experimentally investigate the effect of fluid rheology on wicking dynamics in paper-based LFA (lateral flow assay) using a NaCMC (sodium carboxymethyl cellulose)–water solution and human blood. We develop a saturation-based numerical framework to simulate the wicking phenomenon in paper-based porous strip using experimentally estimated effective viscosity of the solution. Increasing the NaCMC concentration leads to higher liquid entry pressure and enhances flow heterogeneity. Raman analysis unveil that the higher NaCMC concentrations result in more stable hydrogen bonding, primarily attributed to the enhanced hydroxyl group intensity, which in turn capable of increasing the effective viscosity by an order of magnitude. Consequently, we find that with increasing the concentration of NaCMC solution, the average wicking length and imbibition velocity decrease. Interestingly, the effective viscosity ratio appears to be less than unity at lower NaCMC concentrations at longer time instants. We show that diffusion and interception mechanisms dominate total trapping efficiency, while the contribution of inertial mechanism remains insignificant. With increase in NaCMC concentration, the diffusion and overall theoretical trapping efficiency follow a non-monotonic trend. The higher NaCMC concentrations in lower axial positions of the paper strip lead to an enhancement of both trapping efficiency and its probability. Pertaining to imbibition of human blood on paper strip, the wicking length and average wicking velocity of blood reduces with increase in hematocrit level and, at times, temporal variation of effective viscosity of blood shows a non-monotonic trend. Moreover, we find that, based on the critical Damk€ohler number, the optimum test line location is shorter for higher hematocrit level and increasing NaCMC concentration. This insight provides the optimum design guideline for LFA with efficient reaction. We believe that the findings of this endeavor are deemed pertinent to shed light on the role of fluid rheology in wicking phenomenon and analyte trapping for the efficient design of LFA, largely used for biochemical analysis of non-Newtonian biofluids.