When taken as a supplement, betaine hydrochloride provides extra hydrochloric acid in the stomach. A major branch of alternative medicine known as naturopathy has long held that low stomach acid is a widespread problem that interferes with digestion and the absorption of nutrients. Betaine hydrochloride is one of the most common recommendations for this proposed condition, along with the more folksy choice of apple cider vinegar.

Betaine without the hydrochloride molecule attached is also sold as a supplement. In this chemically different form, it is called trimethylglycine (TMG). TMG is not acidic, and it has completely different properties. (For more information, see the TMG article.)

Betaine hydrochloride is not an essential nutrient, and no food sources exist.