Meet FDA Guidance for Industry: Testing of Glycerin for Diethylene Glycol with our diethylene glycol (DEG) and ethylene glycol limit standards. This guidance emphasizes the importance of screening raw material for the presence of diethylene glycol. Under cGMPs, drug manufacturers—not just glycerin manufacturers—must test glycerin prior to use to prevent DEG contamination in finished products. The FDA has worked extensively with the USP to modify the glycerin monograph, and these standards support the revised USP method.