The disclosure features a lipid nanoparticle (LNP) formulation comprising a plurality of LNPs and a stabilizing agent that mitigates the degradation of the LNPs or a subpopulation thereof. Lipid nanoparticles further including therapeutics and/or prophylactics such as RNA are useful in the delivery of therapeutics and/or prophylactics to mammalian cells or organs to, for example, regulate polypeptide, protein, or gene expression. Methods of manufacturing LNP formulations and screening for a stabilizing agent are also disclosed.