Glutathione

non-nutrient/non-botanical

Take on an empty stomach

What is it

Glutathione is a tripeptide made of glutamate, cysteine, and glycine that is synthesized in every human cell. It is the body's most abundant intracellular antioxidant and a central player in detoxification, immune function, and cellular redox balance.

How it works

Glutathione cycles between reduced (GSH) and oxidized (GSSG) forms. In its reduced form, GSH donates electrons to neutralize reactive oxygen species, peroxides, and free radicals; the enzyme glutathione peroxidase uses GSH to convert hydrogen peroxide into water. After donating an electron, GSH becomes GSSG and is recycled back to its active form by glutathione reductase using NADPH. Beyond direct antioxidant activity, glutathione is a substrate for glutathione S-transferases, a family of enzymes that conjugate toxins, drugs, and metabolic byproducts to make them water-soluble and excretable in bile and urine. It also regenerates oxidized vitamins C and E and participates in DNA synthesis and immune cell function. Oral glutathione supplementation has historically been considered poorly bioavailable because the tripeptide is broken down in the digestive tract. Newer formulations, including liposomal, sublingual, and acetylated forms, have been developed to improve absorption. The most reliable way to raise intracellular glutathione is often through supplying its precursor amino acid cysteine, typically as N-acetylcysteine (NAC).

Evidence for 5 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Oxidative stress reduction

Grade C

Moderate evidence

Small clinical trials suggest oral and liposomal glutathione can modestly raise blood glutathione levels and reduce markers of oxidative stress. Whether this translates to clinical health outcomes is less well established.

Liver health and detoxification

Grade C

Moderate evidence

Research suggests glutathione supports liver function and may help with non-alcoholic fatty liver disease. Most clinical evidence supports NAC, the precursor to glutathione, rather than oral glutathione directly. NAC is FDA-approved as the antidote for acetaminophen overdose.

Immune support

Grade C

Moderate evidence

Glutathione is essential for lymphocyte function, and depletion is linked to impaired immunity. Research suggests supplementation may support immune function in deficient states, but evidence in healthy adults is limited.

Skin pigmentation

Grade D

Mixed evidence

Some small studies suggest oral or intravenous glutathione may lighten skin pigmentation by reducing melanin production. Evidence quality is low, results are inconsistent, and long-term safety of intravenous use for cosmetic purposes is not established.

Parkinson's disease

Grade F

Limited evidence

Mechanistic interest exists because Parkinson's patients show reduced brain glutathione, but clinical trials of supplemental glutathione for Parkinson's have produced mixed and unconvincing results.

4 commercial forms

Reduced glutathione (GSH)

Standard oral form; bioavailability is poor due to digestive breakdown.

Inexpensive but may not reliably raise intracellular glutathione.

Liposomal glutathione

Encapsulated in phospholipid liposomes to protect from digestion.

Higher bioavailability than standard oral; clinical evidence of raised blood levels.

S-acetyl glutathione

Acetylated form designed to resist digestive breakdown.

Marketed for improved absorption; clinical evidence is emerging but limited.

N-acetylcysteine (NAC)

Cysteine precursor; supports endogenous glutathione synthesis.

Often more effective at raising intracellular glutathione than direct supplementation. Well-studied for many indications.

Dosage

There is no RDA for glutathione because the body synthesizes it. Supplemental doses commonly range from 250 to 1,000 mg per day. Liposomal formulations are typically dosed at 250 to 500 mg per day. For raising endogenous glutathione, N-acetylcysteine at 600 to 1,800 mg per day is often more effective and better studied than direct glutathione supplementation. Intravenous glutathione is used in some clinical settings and bypasses absorption issues entirely.

When and how to take it

WHEN: Take oral glutathione on an empty stomach, ideally 30 minutes before meals or two hours after, to minimize degradation by digestive enzymes. Liposomal forms can be taken with or without food. HOW: For sublingual forms, hold under the tongue for 30 to 60 seconds to allow absorption through the oral mucosa. If using NAC instead, take with water and consider splitting doses morning and evening. Avoid combining with strong oxidants and store away from heat and light.

Food sources

Food	Amount	%DV
Asparagus	1 cup cooked	—
Spinach	1 cup cooked	—
Avocado	1/2 medium	—
Okra	1 cup cooked	—
Garlic	1 clove	—
Whey protein (cysteine source)	1 scoop (25-30g)	—
Eggs (cysteine source)	2 large	—

Safety

Oral glutathione is generally well tolerated with few reported side effects. Some users report bloating, gas, or mild gastrointestinal upset. There is no established Tolerable Upper Intake Level. Inhaled or nebulized glutathione may cause bronchospasm in people with asthma. High intravenous doses have rare reports of allergic reactions. Long-term effects of high-dose supplementation are not well characterized.

Who should be cautious

Pregnant and breastfeeding women should consult a clinician before supplementing due to limited safety data. People with asthma should not use inhaled or nebulized forms without medical supervision. Those with active cancer or undergoing chemotherapy should discuss with their oncologist. Anyone with sulfa allergies should be cautious given glutathione contains sulfur.

Interactions

Glutathione may interact with chemotherapy drugs by altering their oxidative mechanism of action; people undergoing cancer treatment should consult their oncologist before supplementing. It may modulate the effects of acetaminophen (paracetamol), which depletes glutathione in overdose; NAC is used as the antidote. Glutathione's role in detoxification may theoretically affect the metabolism of various drugs, though clinically significant interactions are not well documented.

Frequently asked questions

Does oral glutathione actually work?⌄

Older studies suggested poor bioavailability, but newer research, especially with liposomal and acetylated forms, indicates oral glutathione can raise blood levels. For raising tissue glutathione, N-acetylcysteine remains a well-supported alternative.

What's the difference between glutathione and NAC?⌄

Glutathione is the active tripeptide antioxidant. NAC (N-acetylcysteine) is a precursor that supplies cysteine, the limiting amino acid for glutathione synthesis. NAC is typically cheaper, better studied, and reliably raises intracellular glutathione.

Can glutathione lighten skin?⌄

Some small studies suggest a modest skin-lightening effect, but evidence is low quality. Intravenous glutathione for cosmetic skin lightening has not been proven safe or effective and is not FDA-approved for this use.

Is it safe to take glutathione daily?⌄

Short-term daily use of oral glutathione appears safe in healthy adults. Long-term safety data are limited. Consult a clinician if you have underlying conditions or are taking medications.

Should glutathione be taken on an empty stomach?⌄

Standard oral glutathione is best taken on an empty stomach to minimize digestive degradation. Liposomal forms tolerate food better. Sublingual forms should be held under the tongue away from meals.

References

Wikidata: Glutathione — Wikidata link
PubChem: Glutathione (CID 124886) — PubChem link

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Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you're pregnant, breastfeeding, on medications, or managing a chronic condition.