What is Betaine Hydrochloric Acid? GERD: Acid reflux can be caused by a lack of Hydrochloric acid (also called HCL, HCL acid, or betaine hydrochloride in supplement form), which is considered one of the most important fluids (or “juices”) found in the human body. Betaine HCl or Hydrochloric acid or Betaine Hydrochloride is a supplement that is normally recommended when