Trimethylglycine (TMG)

TMG · Betaine · Betaine Anhydrous · Glycine Betaine

Snapshot

Indications	Contraindications
Elevated homocysteine¹ Classical homocystinuria¹ Lower-body strength² Vertical jump performance² Fatty liver enzyme elevation³

Trimethylglycine (TMG), also called betaine, is glycine carrying three methyl groups, found in beets and whole grains, and it donates methyl groups that convert homocysteine to methionine. Supplementation is used to lower elevated homocysteine, and betaine is part of management of classical homocystinuria¹.

A meta-analysis of chronic supplementation in healthy adults found improved maximal strength, mainly in the lower body, and vertical jump, with no clear effect on upper-body strength or muscular endurance². Pilot trials in fatty liver disease found declines in liver enzymes and other markers of liver injury. In mice, a 2021 study found betaine prevented and reversed behavioral deficits and synaptic dysfunction after repeated ketamine exposure; no human trial has tested it. About 490 products list trimethylglycine, mostly capsules and powders; see Form comparison.

Higher-dose supplementation raised total cholesterol in meta-analyses, while lower doses lowered homocysteine without that lipid effect⁴. LiverTox rates betaine an unlikely cause of clinically apparent liver injury⁵.

Last updated October 15, 2026. Read how we make monographs.

In the full monograph

64 sources, 49 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources