get a fix - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Obtain a needed dose of something, especially but not necessarily a narcotic drug. For example, Heroin addicts will do anything to get their fix, or Chris referred to her daily swim in the pool as her chlorine fix. The noun fix has been used for a narcotic dose since the 1930s, and was extended to other compulsively sought things about two decades later. Also see get a fix on.