NAC (N-Acetyl Cysteine): What It Is and 600 mg vs. 900 mg

NAC stands for N-acetyl-L-cysteine. It's a form of the amino acid cysteine, and it's been sold in the U.S. as a supplement for decades [1].

Here's what it is, how to pick a strength, and what to look for on the label.

The quick answer

• NAC is a form of the amino acid cysteine (N-acetyl-L-cysteine).
• 600 mg vs. 900 mg is the amount per capsule. Same ingredient, different strength.
• Ours comes in both, in vegetarian capsules from our Professional Line.

See NAC Capsules →

What NAC is

N-acetyl-L-cysteine is cysteine with an acetyl group attached. Cysteine is an amino acid, one of the building blocks of protein. FDA notes that NAC-containing products labeled as dietary supplements have been sold in the U.S. for over 30 years [1].

NAC's regulatory status, in short

NAC was first approved as a drug, which created a legal question about selling it as a supplement. In August 2022, FDA issued guidance saying it intends to exercise enforcement discretion for NAC products labeled as dietary supplements that otherwise follow the law [1][2]. We cover the details in our companion article on NAC and the FDA.

600 mg or 900 mg?

Both are N-acetyl cysteine in vegetarian capsules. The 600 mg bottle is our everyday strength: 1 capsule per serving, 120 capsules. The 900 mg bottle gives you more NAC per capsule. Follow the suggested use on your bottle, or ask your health care provider which fits you.

Taste and smell

NAC has a natural sulfur smell, so a faint odor when you open the bottle is normal.

NAC label checklist

• Amount per capsule and per serving.
• Capsule type: vegetarian or gelatin.
• Other ingredients, kept short.
• Manufacturing: a GMP-certified facility and lab testing.
• Suggested use printed clearly.

Why we made our NAC this way

Our NAC against that checklist: - Two strengths: 600 mg (120 capsules, 1 per serving) and 900 mg. - Vegetarian capsules; 600 mg other ingredients are veggie capsule, microcrystalline cellulose and magnesium stearate. - Non-GMO, gluten-free, lab verified, made in a GMP-certified facility. - 60-day money-back guarantee.

Shop the products mentioned:

• NAC Capsules: 600 mg or 900 mg N-acetyl cysteine.
• Ultimate Essentials Pack: NAC with fish oil, zinc, B-complex and ADK.
• Zinc Complex Capsules: zinc bisglycinate 30 mg with B2, B6 and molybdenum.

Taking medication, pregnant or nursing? Check with your health care provider before starting NAC.

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These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

FAQ

What is NAC? N-acetyl-L-cysteine, a form of the amino acid cysteine.

Is NAC legal to sell as a supplement? FDA's August 2022 guidance says it intends to exercise enforcement discretion for NAC products labeled as dietary supplements that otherwise comply with the law [1].

What's the difference between NAC 600 mg and 900 mg? Only the amount per capsule. Both are the same N-acetyl cysteine in vegetarian capsules.

Why does NAC smell like sulfur? Cysteine contains sulfur, so a mild sulfur smell is normal.

References

1. U.S. FDA. Guidance for Industry: Policy Regarding N-acetyl-L-cysteine (August 2022). https://www.fda.gov/regulatory-information/search-fda-guidance-documents/guidance-industry-policy-regarding-n-acetyl-l-cysteine
2. Federal Register. Policy Regarding N-acetyl-L-cysteine; Guidance for Industry; Availability (Aug 2, 2022). https://www.federalregister.gov/documents/2022/08/02/2022-16499/policy-regarding-n-acetyl-l-cysteine-guidance-for-industry-availability