VitalMatrix
Amino AcidsModerate

NAC

Also known as N-Acetyl Cysteine, N-Acetyl-L-Cysteine

N-Acetyl Cysteine (NAC) is a stable, bioavailable precursor to cysteine, the rate-limiting amino acid for glutathione synthesis. It is one of the best-studied compounds for restoring antioxidant capacity, protecting the liver, and supporting lung mucus clearance. It is used in emergency medicine (paracetamol overdose) and has growing evidence for OCD, addiction, and mental health.

AntioxidantLung healthBrain healthLiver health
By the Vital Matrix Editorial TeamReviewed by the Vital Matrix Research TeamLast updated June 25, 2026Moderate3 citations
Where to buy(affiliate links — we may earn a commission, which never changes our ratings)Nootropics DepotiHerb

Benefits

Raises glutathione levels

Strong

NAC is the most reliable oral way to raise intracellular glutathione, the body's master antioxidant and detoxification molecule.

Supports respiratory health

Moderate

Used clinically to thin mucus and improve lung function in COPD and chronic bronchitis.

Protects the liver

Strong

Standard hospital treatment for paracetamol (acetaminophen) overdose; also has evidence for non-alcoholic fatty liver disease.

May help with OCD and compulsive behaviours

Preliminary

Early small trials suggested benefit for compulsive behaviours, but a larger phase III trial in OCD found no effect versus placebo.

Pros & cons

Pros

  • Raises glutathione, one of the most important antioxidant actions available
  • Very well studied in clinical settings
  • Supports liver, lung, and mental health across multiple pathways

Cons

  • GI side effects at higher doses
  • Regulatory uncertainty (FDA attempted to restrict OTC sale in the US)
  • High doses may theoretically impair some exercise adaptation signals
  • Long-term use associated with anhedonia (emotional blunting) in some users, cycle with breaks

Side effects

GI upset

Nausea and loose stools are common at higher doses; taking with food helps.

Mild

Rotten-egg smell

The sulphur content can cause breath and body odour changes at higher doses.

Mild

Anhedonia with long-term use

Some users report emotional blunting or reduced ability to feel pleasure (anhedonia) with sustained NAC supplementation. The proposed mechanism is excessive glutathione activity dampening dopaminergic signalling. Taking periodic breaks is advisable for long-term users.

Moderate

How to take it

Typical dose

600–1,800 mg per day in divided doses

Timing

With food to reduce GI upset

Common forms

NAC capsulesNAC powderEffervescent tablets

Tip: 600 mg twice daily is a common protocol. Higher doses (1,200–1,800 mg) are used in clinical studies for OCD and liver support.

What the research says

  1. [1]NAC and glutathione

    Strong

    Oral NAC reliably increases blood and tissue glutathione levels across a wide range of populations and conditions.

    Clinical trials · 2018PubMed

  2. [2]NAC and OCD / compulsive behaviours

    Preliminary

    Early small trials suggested benefit, but a phase III RCT found no evidence that NAC reduces OCD symptoms compared with placebo.

    RCTs · 2022PubMed

  3. [3]NAC and COPD

    Moderate

    High-dose NAC reduces exacerbations and improves lung function in chronic obstructive pulmonary disease.

    Meta-analyses · 2017PubMed

How NAC interacts

Synergies, absorption effects, and cautions between NAC and other supplements in the matrix.

NAC and its direct connections · click a node to open its guide

Synergy
Glycine

NAC provides cysteine while glycine provides another rate-limiting precursor; together they are more effective at raising glutathione than either alone (GlyNAC protocol).

Compare the pairing
Synergy
Vitamin C

Vitamin C regenerates oxidised glutathione back to its active form, amplifying NAC's antioxidant effect.

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Use with care
Zinc

NAC's chelating action can reduce zinc levels with high chronic doses; supplementing zinc alongside long-term NAC use is advisable.

Compare the pairing
Use with care
Copper

NAC may chelate copper at high doses; monitor copper status with long-term high-dose NAC use.

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Synergy
Magnesium

Magnesium supports glutathione enzyme activity alongside NAC.

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Synergy
Coenzyme Q10 (CoQ10)

Two antioxidants that defend mitochondria and cell membranes through complementary mechanisms.

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See it on the matrix

Frequently asked questions

What is NAC used for?

NAC is most commonly used for antioxidant, lung health, brain health, and liver health. NAC is the most reliable oral way to raise intracellular glutathione, the body's master antioxidant and detoxification molecule.

How much NAC should I take?

A typical dose is 600–1,800 mg per day in divided doses. 600 mg twice daily is a common protocol. Higher doses (1,200–1,800 mg) are used in clinical studies for OCD and liver support. Start at the lower end and confirm the right dose for you with a healthcare professional.

When is the best time to take NAC?

Recommended timing: With food to reduce GI upset.

What are the side effects of NAC?

Reported side effects include gi upset, rotten-egg smell, and anhedonia with long-term use. Nausea and loose stools are common at higher doses; taking with food helps.

Who should be careful with NAC?

Do not combine with nitroglycerin or nitrate drugs (may cause severe hypotension). Speak with a healthcare professional if any of these apply to you.

Important cautions

  • Do not combine with nitroglycerin or nitrate drugs (may cause severe hypotension).
  • Long-term continuous use may cause anhedonia or emotional blunting in some people; consider cycling (e.g. 8 weeks on, 2–4 weeks off).
  • NAC has mild heavy-metal chelating properties, this can be beneficial for reducing toxic metal burden, but high chronic doses may also lower zinc and copper levels. Consider supplementing both minerals if using NAC long-term at doses above 1,200 mg/day.
  • Very high doses may blunt some adaptations from endurance exercise.
  • Check local regulations, OTC availability varies by country.

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Compare NAC with

Weighing your options? See how NAC stacks up against similar supplements.

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