L-threonine
L-threonine suppliers and sourcing guide
L-threonine is an essential amino acid with two chiral centers. Commercial L-threonine is made by bacterial fermentation of sugars, mostly with Escherichia coli strains, then purified and crystallized. Much of world output is feed grade, so brands buying for supplements and foods should ask for food or USP grade. It is a white crystalline powder used mostly in amino acid blends.
- Category
- Proteins and amino acids
- Also known as
- Threonine · L-Thr · (2S,3R)-2-Amino-3-hydroxybutanoic acid
- Facts checked
- November 2026
Forms and grades of L-threonine
Suppliers sell different products under the same name. Specify the one you need.
Crystalline
Standard fine crystalline powder for capsules, tablets and dry blends.
Fermented (plant-sugar) grade
L-threonine made by bacterial fermentation of corn, cassava or beet sugar; the source and any vegan statement appear on the supplier's spec.
USP grade
L-threonine tested to the USP monograph, used where a compendial grade is required for supplements.
Food grade
L-threonine tested to a Food Chemicals Codex or supplier food specification for use in foods and drink mixes.
What to check on the COA
Compare each result with your own specification when the lot arrives.
- Identity
- Infrared spectrum matched to a reference standard, plus specific optical rotation, which confirms the L-form of threonine.
- Assay
- Purity on a dried basis by nonaqueous titration or HPLC, reported against the USP, FCC or supplier specification.
- Related substances
- Other amino acids, including allo-threonine and glycine, by HPLC or TLC.
- Loss on drying and residue on ignition
- Moisture by loss on drying and inorganic residue as residue on ignition (sulfated ash), with chloride and sulfate where the specification lists them.
- Heavy metals and microbiology
- Lead, arsenic, cadmium and mercury by ICP-MS, plus total plate count, yeast and mold, E. coli and Salmonella.
Storage, lots and expiry
Storage and shelf life
Store L-threonine in tightly closed, lined containers in a cool, dry place away from light and strong odors, and reseal opened packs promptly. Shelf life or retest date is set by the supplier's specification; assay, loss on drying and micro are the usual retest points for older stock.
Lots and expiry dates
Record assay and grade for each lot and confirm the paperwork says food or USP grade, not feed grade. Rotate stock FEFO.
Regulatory status
Facts from regulators and standards bodies, each linked to its source.
21 CFR 172.320 lists L-threonine among the amino acids that may be safely used as nutrients added to foods.
Source: ecfr.gov (opens in a new tab)Under 21 CFR 172.320, added plus naturally present L-threonine may not exceed 5.0 percent by weight of the total protein of the finished food.
Source: ecfr.gov (opens in a new tab)FDA's Substances Added to Food inventory lists L-threonine with the technical effects flavor enhancer, flavoring agent or adjuvant, and nutrient supplement.
Source: hfpappexternal.fda.gov (opens in a new tab)Health Canada's Workout Supplements monograph lists L-threonine among its essential amino acids, with a dose range of 70 mg to 301 mg per day.
Source: webprod.hc-sc.gc.ca (opens in a new tab)
This is general information, not regulatory advice. Status differs by country and by how the ingredient is used, so check the rules for your product and market.
L-threonine suppliers
Manufacturers and distributors whose own websites say they sell it.
We are checking L-threonine suppliers now
Every listing is checked against the supplier’s own website before it goes live, so this list fills in over the coming weeks. The specs and COA checklist above are ready today.
Sell L-threonine? Request a listingFrequently asked questions
What forms of L-threonine can brands buy?
Common forms include crystalline, fermented (plant-sugar) grade, uSP grade and food grade. Ask each supplier for the specification sheet of the exact grade they quote.
What should the COA for L-threonine include?
Expect identity, assay, related substances, loss on drying and residue on ignition and heavy metals and microbiology, each with its method, specification and result for that lot.
How should L-threonine be stored?
Store L-threonine in tightly closed, lined containers in a cool, dry place away from light and strong odors, and reseal opened packs promptly. Shelf life or retest date is set by the supplier's specification; assay, loss on drying and micro are the usual retest points for older stock.
What is the regulatory status of L-threonine?
21 CFR 172.320 lists L-threonine among the amino acids that may be safely used as nutrients added to foods. Under 21 CFR 172.320, added plus naturally present L-threonine may not exceed 5.0 percent by weight of the total protein of the finished food. FDA's Substances Added to Food inventory lists L-threonine with the technical effects flavor enhancer, flavoring agent or adjuvant, and nutrient supplement. Health Canada's Workout Supplements monograph lists L-threonine among its essential amino acids, with a dose range of 70 mg to 301 mg per day.
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