Hydrogel microparticles have been extensively used in the field of medical diagnostics for detecting targets ranging from proteins to nucleic acids. However, little is known about how the shape of hydrogel particles impacts the signal from a bioassay. In this article, we analyze the flux into porous hydrogel particles to develop scaling laws for the signal from a point-of-care bioassay. The signal can be increased by increasing the ratio of the surface area of the hydrogel particle to the two-dimensional projected imaging area used for analysis. We show that adding internal surface area to hydrogel particles increases the assay signal in a biotin-streptavidin bioassay. We also demonstrate the application of this technique to a protein-based assay for thyroid-stimulating hormone, reducing the limit of detection of the assay sixfold by changing particle shape. We anticipate that these strategies can be used broadly to optimize hydrogel-based systems for point-of-care diagnostics.