N-acetyl cysteine
N-acetyl cysteine suppliers and sourcing guide
N-acetyl cysteine (NAC) is the N-acetylated form of the amino acid L-cysteine. It is made synthetically by acetylating L-cysteine, usually with acetic anhydride, then purified and crystallized. Brands buy it as a white crystalline powder with a slight sulfur and vinegar odor, tested to the USP acetylcysteine monograph, mostly for capsules and tablets.
- Category
- Proteins and amino acids
- Also known as
- NAC · N-Acetyl-L-cysteine · Acetylcysteine · L-alpha-Acetamido-beta-mercaptopropionic acid
- Facts checked
- November 2026
Forms and grades of n-acetyl cysteine
Suppliers sell different products under the same name. Specify the one you need.
USP grade powder
Crystalline powder tested to the USP acetylcysteine monograph, the usual grade for capsules.
Granular grade
Coarser, free-flowing granules made for direct-compression tableting and high-speed encapsulation.
Coated or encapsulated
NAC coated with a fat or polymer layer to cut odor transfer and moisture pickup in multi-ingredient blends.
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 for the L-form.
- Assay
- Purity on a dried basis by titration or HPLC, reported against the USP acetylcysteine monograph or supplier specification.
- Related substances
- L-cystine, L-cysteine and N,N'-diacetylcystine by HPLC; the disulfide forms rise when NAC is exposed to air and moisture.
- Loss on drying and residue on ignition
- Moisture by loss on drying and inorganic residue as residue on ignition.
- 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 NAC in tightly closed, lined containers in a cool, dry place away from light, and reseal opened packs promptly, since air and moisture oxidize it to the disulfide and strengthen its odor. Keep it apart from flavors and finished goods that could pick up the smell. Shelf life or retest date is set by the supplier's specification; assay and related substances are the key retest points.
Lots and expiry dates
Record assay and the related-substances result (especially diacetylcystine) for each lot, and note any odor or color change on receipt. Rotate stock FEFO.
Regulatory status
Facts from regulators and standards bodies, each linked to its source.
In a March 31, 2022 response to citizen petitions from CRN and NPA, FDA confirmed that NAC is excluded from the definition of a dietary supplement.
Source: fda.gov (opens in a new tab)FDA has issued final guidance stating its intent to exercise enforcement discretion for certain NAC-containing products labeled as dietary supplements.
Source: fda.gov (opens in a new tab)Health Canada's N-acetyl-L-cysteine natural health product monograph lists a synthetic preparation.
Source: webprod.hc-sc.gc.ca (opens in a new tab)The monograph sets an adult dose not to exceed 600 mg per day and excludes foods or food-like dosage forms.
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.
N-acetyl cysteine suppliers
Manufacturers and distributors whose own websites say they sell it.
We are checking n-acetyl cysteine 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 n-acetyl cysteine? Request a listingFrequently asked questions
What forms of n-acetyl cysteine can brands buy?
Common forms include uSP grade powder, granular grade and coated or encapsulated. Ask each supplier for the specification sheet of the exact grade they quote.
What should the COA for n-acetyl cysteine 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 n-acetyl cysteine be stored?
Store NAC in tightly closed, lined containers in a cool, dry place away from light, and reseal opened packs promptly, since air and moisture oxidize it to the disulfide and strengthen its odor. Keep it apart from flavors and finished goods that could pick up the smell. Shelf life or retest date is set by the supplier's specification; assay and related substances are the key retest points.
What is the regulatory status of n-acetyl cysteine?
In a March 31, 2022 response to citizen petitions from CRN and NPA, FDA confirmed that NAC is excluded from the definition of a dietary supplement. FDA has issued final guidance stating its intent to exercise enforcement discretion for certain NAC-containing products labeled as dietary supplements. Health Canada's N-acetyl-L-cysteine natural health product monograph lists a synthetic preparation. The monograph sets an adult dose not to exceed 600 mg per day and excludes foods or food-like dosage forms.
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