What Is TMG (Trimethylglycine)? UK Guide

Vitality Supplements · Ingredient Guide

What is TMG?

A clear, factual guide to TMG (trimethylglycine), also known as betaine — what this methyl donor is, its forms, why it is so often paired with NMN, and the one authorised claim for betaine and the exact condition it depends on. TMG is a food supplement.

Last updated July 2026 · Written by Vitality Supplements Editorial Team · ~2,400 words · 9 min read
Food supplement information — not medical advice
UK manufactured ISO/IEC 17025 batch tested 4.8★ from 2,400+ reviews Evidence-referenced
Quick answer
What is TMG?
TMG stands for trimethylglycine — the same compound also known as betaine (specifically betaine anhydrous). It is a methyl donor: a molecule that carries three methyl groups it can hand off in the body's methylation reactions. It occurs naturally in foods such as beetroot (from which the name betaine comes), wheat bran and spinach. In supplements it is frequently paired with NMN, because NMN-driven pathways use up methyl groups, and TMG helps replenish the methyl pool. It is sold as a food supplement in the UK. There is one authorised claim — for betaine and normal homocysteine metabolism — which applies only at a daily intake of 1.5g of betaine.
Key takeaways
  • TMG = trimethylglycine = betaine (betaine anhydrous).
  • It is a methyl donor — it supplies methyl groups used in methylation reactions.
  • Found naturally in beetroot, wheat bran and spinach.
  • Commonly paired with NMN because methylation pathways consume methyl groups.
  • Sold as capsules or powder; often standardised betaine anhydrous.
  • Authorised claim: betaine contributes to normal homocysteine metabolism — only at a daily intake of 1.5g of betaine.
The basics

What TMG actually is

TMG is short for trimethylglycine — an amino-acid derivative that is chemically the amino acid glycine carrying three methyl groups. It is the very same compound as betaine (you will see it labelled "betaine anhydrous"): the name betaine comes from Beta vulgaris, the beet, where it was first identified. So TMG and betaine are two names for one molecule.

The defining feature of TMG is that it is a methyl donor. Methyl groups (a carbon with three hydrogens) are constantly moved around in the body during a process called methylation, and TMG is one of the molecules that can donate them. It occurs naturally in the diet — beetroot, wheat bran, spinach and shellfish are notable sources. As a supplement it is sold as a food supplement in the UK, and this guide stays factual about what it is and how it is used.

One molecule, two names: trimethylglycine and betaine — a methyl donor.
On the label

Forms & sources

TMG is a well-defined single compound, so there is little of the form confusion seen with some ingredients. The main things to read on a label are whether it is listed as trimethylglycine or betaine anhydrous (the same thing), the amount per serving, and whether it is a standalone product or part of a combination such as an NMN complex.

What you will see Detail Notes
Name on label TMG / Trimethylglycine / Betaine anhydrous All the same compound. "Anhydrous" simply means the dry, water-free form.
Format Capsules or powder Powder is easy to scale; capsules give a measured dose.
Standalone serving Commonly ~500–1000mg, up to 1.5g+ The authorised betaine claim applies at 1.5g/day (see below).
In an NMN complex e.g. 750mg TMG alongside NMN Included to support methylation when taking NMN.
Dietary sources Beetroot, wheat bran, spinach, shellfish TMG also occurs naturally in a normal diet.
Verification HPLC + Certificate of Analysis Confirms identity and purity of the betaine used.

As always, a good product states the exact amount of TMG per serving and can provide a Certificate of Analysis. If you are looking at a combination product, check how much TMG it actually contains rather than relying on the headline blend total.

The NMN connection

Why TMG is paired with NMN

If you have looked at NMN or NAD-support products, you will often see TMG in the same formula. The reasoning is about methylation. When the body processes and clears certain compounds — including some steps connected with NAD-related pathways — it uses methyl groups, drawing on the body's methyl pool (centred on a molecule called SAMe). The thinking behind adding TMG is that, as a methyl donor, it helps replenish those methyl groups, which is why formulators pair the two.

Methylation, simply put
Passing along methyl groups. Methylation is the transfer of methyl groups between molecules — a routine part of how the body builds and processes many compounds.
Why NMN users add TMG
Replenishing the pool. Because methylation reactions consume methyl groups, TMG is included as a methyl donor to help top the pool back up.
A common combination
NMN + TMG. The two are frequently formulated together, which is why you will see them combined in NAD-support products.
Learn more about NMN
Start with the basics. See our what is NMN guide for the wider NAD context that TMG is usually paired with.

This explains the rationale for pairing TMG with NMN; it is not a health claim. For the wider picture, see our what is NMN guide and our what is NAD explainer.

The one authorised claim

Betaine & homocysteine — the condition

There is one authorised health claim relevant to TMG, and it is worded for betaine: "betaine contributes to normal homocysteine metabolism." This claim may be used only when the specific condition is met: the beneficial effect is obtained with a daily intake of 1.5g of betaine. In other words, the claim applies at 1.5g/day — not at lower amounts.

Because of that condition, we are careful: a product that provides less than 1.5g of betaine (TMG) per day — for example a smaller dose within an NMN complex — does not meet the threshold, so the claim should not be attached to it. There is also a standard caution associated with betaine: do not exceed a daily intake of 4g. Outside of this single authorised statement and its 1.5g/day condition, we keep to the facts: TMG is a methyl donor, paired with NMN to support methylation.

The betaine homocysteine claim applies only at 1.5g of betaine per day.
Common questions

TMG FAQ

Yes. TMG (trimethylglycine) and betaine are the same compound — you will often see it on labels as "betaine anhydrous". The name betaine comes from the beet, where it was first identified.
A methyl donor is a molecule that can hand off methyl groups (a carbon with three hydrogens) to other molecules during methylation. TMG carries three such groups, which is where the "tri-methyl" in trimethylglycine comes from.
Methylation reactions in the body consume methyl groups. Because TMG is a methyl donor, formulators add it to NMN and other NAD-support products with the aim of helping replenish the methyl pool. This is the rationale for the pairing, not a health claim. See our what is NMN guide for context.
Yes, worded for betaine: "betaine contributes to normal homocysteine metabolism." It may be used only when the beneficial effect is obtained — that is, at a daily intake of 1.5g of betaine. Products providing less than 1.5g/day do not meet the condition. A standard caution applies: do not exceed 4g of betaine per day.
Standalone products commonly provide around 500mg to 1.5g or more per day, while an NMN complex might include a smaller amount (for example 750mg) to support methylation. Always check the exact amount of TMG per serving. This describes what products offer rather than a recommended dose; consult a healthcare professional before starting any supplement.
As a general precaution TMG is not recommended for anyone under 18, or during pregnancy or breastfeeding, and anyone taking medication or managing a health condition should speak to a healthcare professional first. Do not exceed 4g of betaine per day, and introduce one product at a time.

TMG, paired with NMN

Our NMN + TMG Complex combines 750mg NMN with 750mg trimethylglycine per serving to support methylation alongside NMN — UK-manufactured and independently batch tested, with a Certificate of Analysis available on request.

Shop NMN + TMG Complex → Read: what is NMN?
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About the author. This guide was written and reviewed by the Vitality Supplements Editorial Team, a UK supplement manufacturer. Every batch we produce is independently tested by an ISO/IEC 17025-accredited laboratory, with a Certificate of Analysis available on request.

This article is for general information about food supplements and is not medical advice. TMG (trimethylglycine / betaine) is sold as a food supplement in the UK. The authorised claim that betaine contributes to normal homocysteine metabolism applies only when its condition is met (a daily intake of 1.5g of betaine); do not exceed 4g of betaine per day. Always consult a qualified healthcare professional before starting any supplement, particularly if you are under 18, pregnant, breastfeeding, taking medication or managing a health condition. References available on our research references page.