Glutathione (Total, Free, Oxidized)

Glutathione is a small protein-like molecule made up of three amino acids: glutamic acid, cysteine and glycine. The body makes it itself, mainly in the liver. Inside the cell, glutathione is the main substance that neutralizes harmful oxygen compounds and that helps break down toxins and medicines. By far most glutathione is inside cells, especially red blood cells; there is only a little of it in the blood plasma. The laboratory usually measures the total glutathione in blood or the ratio between the restored and the used form.

• A low amount of glutathione in the red blood cells, without it being established what that means for health
• Rarely: a hereditary deficiency of an enzyme in the glutathione metabolism, which goes with sudden breakdown of red blood cells

An abnormal value on its own usually does not lead to follow-up testing. With anemia or jaundice, the GP looks at the blood count, the reticulocytes, the bilirubin and the LDH, and if needed refers to an internist (specialist in internal medicine) to investigate the cause.

There are no agreed cutoff values for glutathione in blood, and what an abnormal value means has been little studied. The measurement is also technically difficult: glutathione oxidizes quickly after the blood draw, so the result depends strongly on how quickly and how cold the sample was processed. In the only well-described conditions, hereditary deficiencies that cause sudden breakdown of red blood cells, the activity of the enzymes that restore glutathione (glutathione reductase, G6PD) says more than the amount of glutathione itself. An abnormal result in someone without symptoms cannot be interpreted.

• Glutathione oxidizes quickly after the blood draw; the time until processing, the temperature and the tube used largely determine the result.
• By far most glutathione is inside the cell; what is measured in plasma says little about the amount in tissues such as the liver.
• The number and age of the red blood cells affect the result, for example after bleeding or with anemia.
• There are no standardized methods or reference values; results from different laboratories are not comparable.

There are no Dutch figures on how often a low glutathione value occurs, because there is no agreed cutoff value and little research has been done on it. Hereditary deficiencies of enzymes in the glutathione metabolism are rare and uncommon in the Netherlands.

The result says little in people without symptoms. It also adds nothing with long-lasting tiredness: according to the guideline on chronic fatigue syndrome, it has not been shown that supplements reduce those symptoms. With repeated sudden breakdown of red blood cells, the activity of the enzymes involved says more; that is a different test from this one.

• A low value can cause unnecessary worry or wrongly explain symptoms, so that another cause is found later.
• A low value can lead to buying supplements whose benefit has not been shown.

• NVKC, allesovertesten.nl: Glutathionreductase (het enzym dat glutathion herstelt; er is geen NVKC-pagina over glutathion zelf)
• NVKC, allesovertesten.nl: G6PD
• FMS Richtlijnendatabase, richtlijn Chronisch vermoeidheidssyndroom: Dieetinterventies en supplementen