225 ILCS 30/80

(a) Only a person who is issued a license as a dietitian nutritionist under this Act may use the words "licensed dietitian nutritionist", "dietitian nutritionist", or "dietitian" or the letters "L.D.N." or hold oneself out as qualified or licensed to practice under this Act in connection with his or her name. (b) A licensee shall include in every advertisement for services regulated under this Act his or her title as it appears on the license or the initials authorized under this Act. Advertisements shall not include false, fraudulent, deceptive, or misleading material or guarantees of success. (c) Use of an earned, federally trademarked nutrition credential is not prohibited, but such use does not give an individual the right to practice dietetics or nutrition or provide medical nutrition therapy unless the individual is licensed under this Act.