What are the side effects of glutathione?

This is a tricky question, since this question usually comes up with drugs or pharmaceuticals. We want to know if we take drug X, what are its side effects?

So naturally based on this reasoning, we may ask if we take glutathione, side effects that may follow would be what? To begin with, glutathione is a naturally occurring substance in each of our cells. So we will use the terms glutathione and natural glutathione interchangeably on this page.

Side effects and benefits of Glutathione

“Glutathione side effects” can be used as a term that describes the positive effect of optimal glutathione levels on our health. When cells have abundant glutathione precursors and cofactors, and are able to manufacture glutathione without any impediments in the amounts and at a pace they need, these positive glutathione side effects are:

  • Improved immune function (resistance to infection and various pathogens, timely elimination of cancerous cells, proper regulation of immune response)
  • Improved energy levels
  • Improved mental focus
  • Improved physical strength and muscle function
  • Whiten skin complexion

All of the above become possible because glutathione works on a cellular level to:

  • Eliminate toxins
  • Eliminate carcinogens
  • Provide an adequate antioxidant response
  • Protect from ionizing radiation
  • Correct gene expression
  • Ensure proper synthesis, protection and repair of DNA
  • Ensure proper expression of enzymes

Bronchial Constriction

A study published in the August 1997 issue of the “American Journal of Respiratory and Critical Care Medicine” pointed out that inhaled glutathione supplements can cause a severe reduction in the size of the airways, bronchoconstriction, leading to breathing difficulties in predisposed patients. Glutathione supplements administered through inhalation are effective in reducing the oxidative damage created by environmental and inflammatory processes.

However, as the study suggests, nebulized glutathione can lead to the local formation of sulfite, a substance suspected to reduce the caliber of the airway and worsen an asthmatics breathing. Sulfite gives the glutathione inhaled preparation a characteristic “rotten egg odor.” Bronchial constriction manifests by cough, difficulty breathing and breathlessness, making nebulized glutathione unsuitable for patients with asthma.

Gastrointestinal Side Effects

Drugs.com cites abdominal cramps and bloating as possible gastrointestinal side effects for the use of oral glutathione precursors, usually in powder form. Oral glutathione supplementation is usually done through supplying glutathione in its precursor form because it is more resistant to stomach acids and digestive enzymes. The manufacturers assert that the gastrointestinal adverse effects should be minimal when the powder is reconstituted and rehydrated properly.


According to Drugs.com, powdered oral glutathione precursors may cause mild allergic reactions. Most commonly, some patients suffer from a transient rash resembling urticaria upon ingestion of the product. Because glutathione precursor oral preparations are bovine milk extracts, patients with milk allergies may be more likely to develop allergic reactions to the product. The allergy is usually self-limited and abates upon discontinuation of the product.

Side Effects Of Glutathione : Raising it with SAM

Natural glutathione may also be raised to a certain extend with SAM or S-Adenosyl-Methionine. SAM is also a drug, it is expensive to make, and may not mix well with other antidepressants.

Glutathione side effects from raising it with SAM may include:

  • Dry Mouth
  • Agitation
  • Gastrointestinal Problems

Side Effects Of Glutathione : Raising it with L-Cysteine

L-Cysteine or free cysteine has a negligible impact on raising glutathione levels, as it is quickly oxidized in the digestive tract just like oral glutathione.

In addition, possible glutathione side effects of raising it with L-Cysteine include:

  • Hyperhomocysteinemia (a toxic condition marked by excessive cysteine)
  • Toxic By-Products like the OH free radical. This defeats its purpose as an antioxidant.

Side Effects Of Glutathione : Raising it with L-Methionine

Methionine is also a building block for raising glutathione. However, above certain doses it can be toxic. Also, methionine is a precursor for homocysteine, which has been identified as a high risk factor in the development of hardening of the arteries.

Side Effects Of Glutathione : Raising it with Silymarin

What are the side effects of raising glutathione with silymarin or milk thistle? Possible glutathione side effects are:

  • Gas
  • Cramps
  • Diarrhea

“Can I take too much or accidentally overdose on glutathione?
What are the side effects of a glutathione overdose?”

When we take the building blocks for glutathione, the cell makes just as much as it needs, and no more. If you take in more building blocks than you need, Immunocal is a protein, so the excess would be used as such in the Krebs cycle. The Krebs cycle is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidization of acetate derived from carbohydrates, fats and proteins into carbon dioxide and water.

Additionally it is noted that overdosing on Immunocal has not been reported.

Always use good sense and follow recommended guidelines when taking any glutathione enhancer, whether it be pharmaceutical (drug) or nutraceutical (food).

What are the side effects of natural glutathione? They are anti-oxidation, immune system boosting, detoxification, energy, and anti-aging.

There are many ways to raise glutathione, so we may also ask what are the glutathione side effects of raising it with several precursors?

The best studied ones are N-acetyl-cysteine and Immunocal. Compare the potential side effects with each one, as well as the lesser ways mentioned above, and weigh them against the positive glutathione side effects that are true of each and every one of these substances.