On May 6, 2024, FDA published a final rule in the Federal Register entitled "Medical Devices; Laboratory Developed Tests" (89 FR 37286) ("LDT Final Rule"). This final rule amends FDA regulations to make explicit that in vitro diagnostic products (IVDs) are devices under the Federal Food, Drug, and Cosmetic Act (FD&C Act) including when the manufacturer of the IVD is a laboratory. FDA has prepared this Small Entity Compliance Guide to assist small entities in complying with the requirements established in FDA regulations as they apply to IVDs, including LDTs.