Detection of biomolecules and cells through the use of fluorescent tags is the most widely used method in gene expression analysis, biomarker-based disease diagnosis, and cell imaging. We demonstrate the ability to amplify fluorescent output using a photonic crystal (PC) surface, thereby boosting detection sensitivity by orders of magnitude, and apply the approach to several life science applications. We achieve fluorescence amplification by two distinct mechanisms: First, intense optical near fields that develop on a the surfaces of a PC slab can be designed to coincide with the absorption wavelength of a fluorophore, resulting in enhanced excitation compared to the same fluorophore excited on an optically inactive surface. Second, PC resonances can be designed to coincide with the fluorophore emission wavelength, enabling enhanced extraction of light. The all-dielectric PC structure offers several important advantages with respect to metalenhanced fluorescence using surface plasmons.