Glutathione Forms Compared: Reduced, Oxidised, Liposomal, Sublingual and S-Acetyl

Buyers now ask about more than one kind of glutathione. Reduced, oxidised, liposomal, sublingual and S-acetyl forms all appear on supplement labels. This guide explains how they differ, what human evidence exists for each, and what to check before you choose one.

What glutathione does: the master antioxidant

Glutathione is a tripeptide made from three amino acids: glutamic acid, cysteine and glycine. It is often called the master antioxidant. At the cellular level, it neutralises free radicals, supports detoxification in the liver and works with antioxidants like vitamin C and vitamin E. Body stores of glutathione can be measured in blood cells, which is how the trials below compare forms. [2]

Why the form matters: glutathione absorption

Glutathione is a peptide, and the gut breaks peptides down. A 2019 review noted that the efficacy of oral glutathione is questioned because of limited absorption and bioavailability. [1] Trial results on glutathione levels after oral glutathione supplementation are mixed. A 6-month trial found oral glutathione raised blood levels. [2] A 4-week trial found no change. [3] New forms aim to protect glutathione or improve uptake.

Reduced glutathione (GSH)

Reduced glutathione, also sold as L-glutathione, is the active form. It is the standard raw material for capsules, tablets and sachets, and it has the most human data. Commercial GSH is made mainly by yeast fermentation. Check the GSH assay by HPLC and the oxidised glutathione content on the COA.

Oxidised glutathione (GSSG)

GSSG is two glutathione molecules joined by a disulfide bond. In a 12-week trial in healthy women, 250 mg a day of either GSSG or GSH tended to lower the melanin index versus placebo. Both forms were well tolerated. [4]

Liposomal glutathione: a delivery system

Liposomal glutathione uses liposomes, tiny vesicles of phospholipids, to encapsulate GSH and protect it during digestion. The aim of this liposomal technology is better glutathione absorption than standard glutathione. The ingredients of a liposomal glutathione are therefore typically reduced glutathione, phospholipids and water or another carrier.

In a 1-month pilot study in 12 healthy adults, oral supplementation with liposomal glutathione at 500 or 1,000 mg a day raised blood glutathione by up to 40% after 2 weeks. Oxidative stress markers fell, including a 35% drop in plasma 8-isoprostane. Natural killer cell activity also rose. The two doses did not differ. [5] The study had no placebo group and was small, so the results are preliminary.

Sublingual glutathione

Sublingual tablets dissolve under the tongue, bypassing the gut. In a 3-week crossover trial in 20 people with metabolic syndrome, a sublingual form raised plasma glutathione more than oral glutathione or N-acetyl cysteine. [6] Two authors worked for the company that makes the sublingual product.

S-acetyl glutathione

S-acetyl glutathione carries an acetyl group on the cysteine thiol. It is made by chemical synthesis rather than fermentation. In 2026, the European Food Safety Authority assessed it as a novel food. It concluded the ingredient is safe at 300 mg a day for adults, excluding pregnant and breastfeeding women. [7] In our PubMed search in October 2026, we found no published efficacy trials of it in people.

Precursors: N-acetyl cysteine

The body makes glutathione from glutamate, cysteine and glycine, and cysteine is usually considered the limiting amino acid. N-acetyl cysteine (NAC) supplies cysteine and is often combined with glutathione or used instead of it. In the sublingual trial, NAC was one of the comparison arms. [6]

Glutathione forms side by side

How much glutathione per day?

Doses in human studies depend on the form:

• Reduced glutathione: 250 to 1,000 mg a day in placebo-controlled trials. [2][3]
• Liposomal glutathione: 500 or 1,000 mg a day in the pilot study. [5]
• S-acetyl glutathione: up to 300 mg a day for adults, the safe intake set by EFSA. [7]

IV glutathione is not a supplement form

Intravenous glutathione is sometimes compared with oral forms. A 2025 systematic review concluded that IV glutathione is contraindicated because of a lack of efficacy and its side effects. [8] For the side effects of glutathione taken by mouth, see our safety guide.

Stability and formulation

Reduced glutathione slowly oxidises to GSSG in air, moisture and heat. A powder that met its assay at manufacture can drift in humid storage. Keep it sealed, cool and dry, and check the retest date. It also has a sulfur odour and an acidic taste, which matter in sachets and effervescent tablets.

Which form should you choose?

For most capsule, tablet and sachet glutathione supplement products, reduced glutathione is the practical choice, with the deepest evidence. For the benefits of glutathione in each area, see glutathione benefits. Liposomal and sublingual forms are newer, with smaller studies. Whatever you choose, match your label claims to the evidence for that exact form.

FC Materials lists L-Glutathione Reduced (N.L.T 98% assay). For other forms, WhatsApp us. See our glutathione supplier page for the COA checklist.

What the research says

• In a 6-month double-blind trial in 54 adults, oral reduced glutathione at 250 or 1,000 mg a day raised blood glutathione. [2] A 4-week trial in 40 adults at 1,000 mg a day found no change. [3]
• In a 1-month pilot study in 12 adults without a placebo group, liposomal glutathione raised blood glutathione by up to 40%. [5]
• In a 3-week crossover trial in 20 adults with metabolic syndrome, sublingual glutathione raised plasma glutathione more than oral glutathione or NAC. Two authors were from the producer. [6]
• EFSA concluded in 2026 that S-acetyl glutathione is safe at 300 mg a day for adults, excluding pregnant and breastfeeding women. [7]

These summaries describe published research on the ingredient. They are not claims for any finished product; claims on finished products must meet the rules of the market where they are sold.

References

1. Dilokthornsakul W, et al. The clinical effect of glutathione on skin color and other related skin conditions: a systematic review. J Cosmet Dermatol. 2019;18(3):728-737. doi:10.1111/jocd.12910
2. Richie JP, et al. Randomized controlled trial of oral glutathione supplementation on body stores of glutathione. Eur J Nutr. 2015;54(2):251-263. doi:10.1007/s00394-014-0706-z
3. Allen J, Bradley RD. Effects of oral glutathione supplementation on systemic oxidative stress biomarkers in human volunteers. J Altern Complement Med. 2011;17(9):827-833. doi:10.1089/acm.2010.0716
4. Weschawalit S, et al. Glutathione and its antiaging and antimelanogenic effects. Clin Cosmet Investig Dermatol. 2017;10:147-153. doi:10.2147/CCID.S128339
5. Sinha R, et al. Oral supplementation with liposomal glutathione elevates body stores of glutathione and markers of immune function. Eur J Clin Nutr. 2018;72(1):105-111. doi:10.1038/ejcn.2017.132
6. Schmitt B, et al. Effects of N-acetylcysteine, oral glutathione (GSH) and a novel sublingual form of GSH on oxidative stress markers: a comparative crossover study. Redox Biol. 2015;6:198-205. doi:10.1016/j.redox.2015.07.012
7. EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA), et al. Safety of S-acetyl glutathione as a novel food pursuant to Regulation (EU) 2015/2283. EFSA J. 2026;24(9):e10258. doi:10.2903/j.efsa.2026.10258
8. Sarkar R, et al. Glutathione as a skin-lightening agent and in melasma: a systematic review. Int J Dermatol. 2025;64(6):992-1004. doi:10.1111/ijd.17535