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NAC

Amino acids
Glutathione · liver

Your intake

Today (logged)
0 mg
0% of 600 mg
Stack potential
0 mg
0% of 600 mg
Target
600 mg
Target Range
Where you are on the ladder0% of target

What each level of nac does

Approximate dose-response bands. Individual response varies — these are starting points, not prescriptions.

  1. Severely lowYOU ARE HERE
    0 mg – 198 mg

    Well below target. Risk of deficiency symptoms tied to glutathione · liver.

  2. Insufficient
    198 mg – 600 mg

    Below the recommended daily target. Long-term adequacy not assured.

  3. Adequate
    600 mg – 900 mg

    Daily target met. Standard nutritional support for glutathione · liver.

  4. Therapeutic
    900 mg – 1200 mg

    Common for specific health goals. Check the evidence for your situation before sustaining this level.

  5. Diminishing returns
    1200 mg – +

    Past the point where extra intake typically helps. Evidence for further benefit is thin.

Overview

N-acetylcysteine — acetylated derivative of the conditionally essential amino acid cysteine. Used clinically as acetaminophen overdose antidote (>50 years), mucolytic, and increasingly studied for psychiatric, pulmonary, and longevity applications via its role as a glutathione precursor.

Functions

  • ●Glutathione (GSH) precursor — supplies the rate-limiting cysteine for synthesis
  • ●Direct free-radical scavenger via thiol group
  • ●Mucolytic — cleaves disulfide bonds in mucus glycoproteins
  • ●Modulates glutamatergic neurotransmission (cysteine-glutamate antiporter)
  • ●Conjugates with toxic acetaminophen metabolite NAPQI

Mechanism

Hydrolysed to L-cysteine, which combines with glutamate and glycine via gamma-glutamylcysteine synthetase (the rate-limiting enzyme) and GSH synthase to produce reduced glutathione. GSH then donates electrons to oxidised substrates and to detoxify xenobiotics. The acetyl group makes NAC more stable and better-absorbed than free L-cysteine.

Benefits

  • ●Standard-of-care antidote for acetaminophen overdose (IV or oral)
  • ●Improves COPD exacerbation rate at 600–1,200 mg twice daily (meta-analyses)
  • ●Modest improvement in OCD, trichotillomania, and skin-picking
  • ●May reduce contrast-induced nephropathy risk (mixed evidence)
  • ●GlyNAC protocol: NAC + glycine improves multiple aging markers in small trials

Deficiency

Not an essential nutrient — cysteine is the relevant precursor and is met by adequate dietary methionine/cysteine intake. Glutathione status may be marginal in chronic illness and aging.

Signs
  • ●Not directly applicable — see cysteine/glutathione status

Excess

Well-tolerated up to ~6 g/day orally; higher IV doses used in overdose. Sulfur metabolites can produce odour and mild GI upset.

Signs
  • ●Sulfur smell (in breath, urine)
  • ●Nausea, vomiting, diarrhea (especially without food)
  • ●Possible vasopressor interaction with nitroglycerin
  • ●Rare bronchospasm in asthmatics (inhaled form)

Forms

  • N-acetyl-L-cysteine (NAC) capsules
    Standard oral form; 600 mg the typical unit dose
  • NAC effervescent / liquid
    Used in acetaminophen overdose; intense sulfur taste
  • Inhaled NAC
    Mucolytic in COPD; under physician guidance
  • IV NAC
    Hospital use only; overdose and contrast-nephropathy protocols

Food sources

  • NAC isn't directly in food · ——
  • Cysteine sources: poultry, eggs · 3 oz / 1 egg200–300 mg cysteine
  • Whey protein · 1 scoop300+ mg cysteine
  • Allium vegetables (garlic, onions) · 1 cloveSulfur compounds, indirect

Supplement forms

N-acetyl-cysteine (NAC) at 600–1,200 mg/day in divided doses. Take on an empty stomach for absorption. Sulfur smell is normal. Don't combine with nitroglycerin without medical supervision. FDA contested NAC's dietary-supplement status briefly (2020-2022) but enforcement discretion has returned to allowing OTC sale.

Bioavailability

Oral bioavailability of intact NAC is low (~10%) due to first-pass metabolism, but conversion to cysteine and incorporation into GSH is reliable. Empty stomach improves uptake. Plasma cysteine peaks at 1–2 h.

Longevity relevance

Glutathione status declines with age. GlyNAC (glycine + NAC, 1.3 g + 1 g of each per day in trials) restored GSH levels and improved mitochondrial function, insulin sensitivity, and inflammatory markers in older adults. Mechanism is well-grounded; outcome trials are early but promising.

Relationships

Synergies (works better with)
  • Glycine · Co-limiting amino acid for GSH synthesis (GlyNAC protocol)
  • Selenium · Glutathione peroxidase requires both for full activity
  • Alpha-lipoic acid, vitamin C · Recycle oxidised glutathione back to active form
Antagonists (competes with / inhibited by)
  • Nitroglycerin · Additive vasodilation and hypotension; avoid concurrent use without supervision
  • Activated charcoal · Adsorbs NAC; separate dosing by 1 hour in overdose protocols

References

About NAC

N-acetyl-cysteine; glutathione precursor, antioxidant, mucolytic. Common dose 600–1200 mg.

Role
Glutathione · liver
Daily target
600 mg (TR)
Also called
nac, n-acetyl-cysteine, n-acetyl cysteine, n-acetylcysteine, acetylcysteine
Click here to learn more about NAC →
Full explainer on Formulate Health — mechanisms, who's commonly deficient, food sources, evidence for supplementation.
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How NAC acts on the body

The mechanisms and systems this nutrient feeds. Click any to drill into what runs on it.

Biochemical pathways
AntioxidantDetox★
Body systems
LongevityLiver★
Biomarkers that move with this nutrient
🩸 ALT🩸 GGT

★ = load-bearing / primary cofactor. Track these in My Journey.