L-Carnitine Guide — Salt Forms, Conversion, and Feed-Additive Status
What L-carnitine is
L-carnitine is an amino acid derivative that transports fatty acids into the mitochondria. In supplements it is used for sports and body-fat applications; in feed, as a nutritional supplement. J-STAGE returns a substantial 2,515 papers (537 from 2020 onward).
It is not a food additive. L-carnitine appears in neither of the lists we maintain — 476 designated additives and 327 existing additives — and is handled as a food raw material.
It is also designated as a feed additive
L-carnitine is designated as a feed additive. In the list published by FAMIC (Food and Agricultural Materials Inspection Center), it appears under the use category “supplementation of nutrients and other effective components in feed”, within “amino acids and related substances”.
In other words it is a material with supply routes for both human and animal applications — the same structure as citric acid. Which law applies depends on whether the finished product is for people or animals, and the specification items and required documents change with it. Stating the application when you request a quotation means we can prepare the right specification from the start.
“Send me L-carnitine” does not settle which of the two it is. Leaving that ambiguous means redoing the documentation later.
Three salt forms — settle the conversion first
FONTIA carries three forms, each with its own CAS number.
- L-Carnitine (free base) — CAS 541-15-1
- L-Carnitine Fumarate — CAS 90471-79-7
- L-Carnitine Tartrate — CAS 36687-82-8
A salt carries the additional molecular weight of its counter-ion, so the same charged weight delivers a different amount of L-carnitine depending on the form. This is the largest practical trap.
Always confirm whether the specification states “as the salt, ○% min.” or “as L-carnitine, ○% min.” When switching form, do not carry the formulation quantity across unchanged — redesign it on an L-carnitine basis. Use the conversion factor stated on the specification; do not proceed on an estimate.
On practical grounds for choosing a form: the free base is more hygroscopic and needs care in handling, while the salts tend to be more stable as powders. The suitable form differs between tableting, powder filling and liquid products, so settle the dosage form before discussing it.
The research attaches to the substance
Searching J-STAGE, “L-carnitine” returns 2,515 papers while “L-carnitine tartrate” returns 1. The research base attaches to L-carnitine itself, not to the salt form.
Choosing a salt is therefore a decision about handling, stability and cost, not a way to strengthen the evidence for a claim — the same structure as fermented versus synthetic GABA. Leave that distinction blurred and the price difference becomes impossible to justify.
The function-claim record is thin
Aggregating the Consumer Affairs Agency’s notifications by functional ingredient name, L-carnitine totals 9 notifications from a single company. Against 2,515 research papers, that record is strikingly thin.
The notified wording runs toward fat burning and energy metabolism:
- “L-carnitine has been reported to increase fat burning after exercise”
- “on single intake, fat in energy metabolism during daily activity (physical activity of 3.8 METs or above)…”
Content per daily intake reference is 750 mg (5 notifications), 500 mg (2) and 900 mg (2).
That the notifications come from one company is worth factoring into your design. Little precedent means few templates of research review to work from. Permissible wording and the intake reference differ by notification, and notification is filed on the responsibility of the notifying party.
What to confirm on the specification
- Form and content basis — free base or salt; “as the salt” or “as L-carnitine”. Settle this first
- Application — human or animal. The governing law and required documents change with it
- Hygroscopicity — particularly for the free base. Confirm handling after opening and storage conditions
- Particle size — what suits differs between tableting and powder filling
- Optical purity — that it is the L-form. Check the specification item for D-form contamination
- Heavy metals and purity tests — compendial or in-house specification
Discussing your requirement
For specifications, samples or a quotation, use the contact form and include the application (human or animal), preferred form, intended daily dose and dosage form. If the form is still undecided, tell us the dosage form and intended quantity and we will propose one.
Related: functional ingredients · feed additives
FAQ
Should I choose the free base or a salt?
The research base attaches to L-carnitine itself (2,515 papers on J-STAGE against 1 for the tartrate), so the salt form does not change the evidence for a claim. Choose on handling, stability and cost — the free base is more hygroscopic, the salts tend to be more stable as powders.
What should I watch when switching form?
A salt carries the counter-ion’s molecular weight, so the same charged weight delivers a different amount of L-carnitine. Check whether the specification reads “as the salt” or “as L-carnitine” and redesign the quantity on an L-carnitine basis, using the conversion factor from the specification rather than an estimate.
Can it be used in feed?
It is designated as a feed additive under “amino acids and related substances”. Note that human and animal applications fall under different laws, with different specification items and documents. Tell us the application when requesting a quotation.
What daily intake is typical?
Notifications show 750 mg (5), 500 mg (2) and 900 mg (2). Note that the total record is 9 notifications from one company, so precedent is limited.
Can it be used in a Foods with Function Claims product?
It can, but the record stands at 9 notifications from a single company. There are 2,515 research papers, but few notification templates to work from — factor that into your design.
Can you supply small quantities for trials?
Yes. Please tell us the application, preferred form, intended daily dose and dosage form.