Glutathione side effects depend almost entirely on how it enters the body. Swallowed, it has a quiet record in trials. Dripped into a vein, the molecule itself was well tolerated in a small trial, but the products used in clinics have caused serious reactions. Breathed in, it narrowed the airways of people with asthma. This page takes each route in turn.
The molecule and its uses are covered in the glutathione guide. This page sits under the longevity goal.
Oral glutathione
The oral trials report little. In a 4-week randomized trial of 60 medical students given 500 mg a day or placebo, both were described as very well tolerated [6]. A 12-week trial in women given 250 mg a day of reduced or oxidized glutathione, with blood monitoring for safety, reported no serious adverse effects [7].
Those are short trials in healthy people. How well oral glutathione is absorbed in the first place is a separate question, covered in whether oral glutathione raises levels in the body.
Intravenous glutathione: the molecule
A randomized, double-blind pilot tested IV glutathione in people with Parkinson’s disease [3]. It randomized 21 people, 11 to glutathione at 1,400 mg three times a week for 4 weeks and 10 to placebo. No one withdrew for side effects in either group, reported adverse events were similar, and the authors identified no safety concerns.
A 2016 review of IV glutathione across medical uses reached a narrower conclusion [8]. Most trials reported no or minimal side effects, but all lasted a few doses or 4 to 12 weeks. No study reported long-term IV use, for skin lightening or any other purpose.
Intravenous glutathione: the products
In January 2019, the FDA received a report of seven patients at one outpatient clinic, each given 1,400 mg of compounded glutathione by IV [1]. Within minutes they developed nausea, vomiting, lightheadedness, chills and body aches. One had low blood pressure and trouble breathing and was taken to a hospital. A separate patient given 2,400 mg developed chills, fever and shaking and was admitted for a possible bloodstream infection.
The agency traced both reports to glutathione powder labeled as a dietary supplement, with potentially high levels of endotoxin, a bacterial contaminant [1]. In August 2026 it reported at least 30 more patients with reactions after IV glutathione compounded by several pharmacies from one lot of supplement-grade ingredient [2].
Those reactions included fever, chills, pain, dizziness, signs of shock and sepsis-like symptoms, with some hospitalizations. Two pharmacies recalled products over elevated endotoxin. The FDA’s message to compounders is that supplement-grade ingredient is not appropriate for injectable drugs [2].
IV glutathione for skin lightening
Clinics advertise IV glutathione for skin lightening [8], and it is the use with the weakest support. A 2025 systematic review found one placebo-controlled trial of IV glutathione for lightening. It concluded that IV glutathione is contraindicated for the purpose, because of lack of efficacy and side effects [5].
The 2016 review adds a longer-term concern: a shift in the skin’s pigment from brown toward red melanin might raise sun-induced skin cancer risk in people who were previously protected [8]. That is a hypothesis the authors raise, not an observed effect. The trials of oral and topical forms are in what trials found on glutathione for skin.
Inhaled glutathione
Nebulized glutathione is the route with a clear harm in a controlled study. In 8 people with mild asthma, a single 600 mg dose caused major airway narrowing [4]. FEV1, a standard measure of how much air can be blown out in one second, fell 19%, against 1% on placebo (p = 0.03).
Four of the eight coughed and three became breathless. A prior dose of salbutamol, an asthma reliever, blocked the effect. The authors attribute it to sulfite formation in the airway [4].
That finding is specific to asthma. In a 6-month trial of inhaled glutathione in 153 people with cystic fibrosis, adverse event rates were similar on glutathione and placebo [9]. That trial also found no clinically relevant improvement in lung function.
What this means for you
For oral glutathione, the trial record shows few side effects over weeks. For IV glutathione, the product and the ingredient grade matter more than the molecule, and no long-term safety data exist. For inhaled glutathione, people with asthma face a documented risk. The injectable evidence as a whole is in what the evidence shows on glutathione injections. Among the sellers reviewed here, the Synergy Rx review covers a seller that lists glutathione injections.