Not medical advice. I am a software engineer, not a physician. This page documents my own protocol and the research I read while building it. Talk to a qualified clinician before changing your supplementation, diet or any treatment. Lab reference ranges quoted here vary by laboratory and by individual.
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N-Acetyl Cysteine (NAC) is the acetylated form of the amino acid L-cysteine. It has been used in clinical medicine for over 50 years, originally as a mucolytic agent to break down thick mucus in respiratory conditions, and later as the standard hospital treatment for acetaminophen (paracetamol) overdose — where it works by rapidly replenishing liver glutathione. NAC provides the rate-limiting substrate for glutathione synthesis, making it arguably the single most impactful supplement for the body's endogenous antioxidant defense system. While the body can synthesize cysteine from methionine, this conversion is slow and often insufficient under conditions of oxidative stress, environmental toxin exposure, or aging.
Glutathione (GSH) is a tripeptide composed of glutamate, cysteine, and glycine. Of these three amino acids, cysteine availability is the bottleneck for synthesis. NAC provides a stable, bioavailable form of cysteine that readily crosses cell membranes and enters the glutathione synthesis pathway. Glutathione is the body's primary intracellular antioxidant, neutralizing hydrogen peroxide, lipid peroxides, and other reactive oxygen species. It also conjugates toxins in the liver's Phase II detoxification, preparing them for excretion via bile or urine.
NAC also functions as a direct chelator of heavy metals including mercury, lead, cadmium, and arsenic. The sulfhydryl (thiol) group on the cysteine molecule binds metal ions, facilitating their excretion. This chelation activity operates independently of glutathione and provides an additional layer of detoxification, particularly relevant for individuals with chronic low-level environmental metal exposure.
Beyond antioxidant and detoxification roles, NAC modulates glutamate neurotransmission by regulating the cystine-glutamate antiporter (system Xc-) in the brain. This mechanism has shown promise in psychiatric research for conditions involving glutamate dysregulation, including OCD, addiction, and depression. NAC also has mucolytic properties — it breaks disulfide bonds in mucus glycoproteins, reducing mucus viscosity in the respiratory tract.
Brand: Thorne — NAC, 500 mg (90 Capsules)
| Time | Dose | Notes |
|---|---|---|
| 4:30 AM (fasted) | 500 mg | First dose fasted for optimal glutathione replenishment after overnight depletion |
| 12:00 PM (lunch) | 500 mg | Second dose to maintain glutathione levels through midday oxidative stress |
| 7:00 PM (dinner) | 500 mg | Third dose for evening liver detoxification support |
Total daily dose: 1,500 mg (1.5 g). The three-times-daily dosing maintains steady cysteine availability for continuous glutathione synthesis. Thorne's formulation avoids the common additives found in lower-quality NAC products. See the full timing context in the Supplement Stack.
Raghu et al. (2021) published a comprehensive review covering NAC's clinical applications across multiple organ systems. The review confirmed NAC's efficacy in replenishing glutathione, reducing oxidative stress markers, and providing clinical benefit in conditions ranging from liver disease to respiratory illness to psychiatric disorders. The authors noted that NAC has one of the strongest safety profiles of any nutraceutical, with adverse effects rare even at high doses. PMID: 34488802
Millea (2009) reviewed NAC's role in liver protection beyond acetaminophen overdose, documenting its efficacy in non-acetaminophen acute liver failure, non-alcoholic fatty liver disease (NAFLD), and chronic liver conditions. The review showed that NAC supplementation reduced liver enzyme elevations (ALT, AST) and improved markers of hepatic glutathione status. PMID: 17177891
Deepmala et al. (2015) conducted a systematic review of NAC in psychiatric disorders, finding evidence of benefit in depression, bipolar disorder, OCD, schizophrenia, and addiction. The mechanism involves modulation of the glutamate system via the cystine-glutamate antiporter, reduction of oxidative stress in the brain, and reduction of neuroinflammation. PMID: 26457580
A 2025 randomized clinical trial published in Frontiers in Immunology examined co-administration of vitamin D and NAC to modulate immunosenescence in older adults with vitamin D deficiency. After 8 weeks, the combined vitamin D + NAC group showed a significant decrease in senescence-associated beta-galactosidase staining compared to vitamin D alone, suggesting NAC enhances anti-aging effects of vitamin D on the immune system. The Johns Hopkins NAC Attack trial — an international phase-III study of oral NAC 1,800 mg twice daily for retinitis pigmentosa — successfully enrolled 485 patients from 31 sites across 7 countries by August 2025, with interim progression data expected in 2028. This represents the largest clinical trial to date investigating NAC for a neurodegenerative condition.
| Test | Why Monitor | Link |
|---|---|---|
| Liver Panel (ALT, AST, GGT) | Primary beneficiary organ; track liver enzymes to confirm hepatoprotective effect | Lab Tests |
| Kidney Panel (Creatinine, BUN) | NAC is renally excreted; confirm kidney function remains stable at 1.5 g/day | Lab Tests |
| CRP (C-Reactive Protein) | Glutathione replenishment reduces oxidative-stress-driven inflammation; CRP tracks the systemic effect | Lab Tests |
Thorne — NAC, 500 mg (90 Capsules)
Price: $31.00
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