Glutathione is a powerful antioxidant made naturally in the body. It is produced from the amino acid methionine, which is converted into cysteine and then into glutathione. Glutathione plays a key role in protecting cells from oxidative damage, supporting detoxification pathways, and helping regulate homocysteine levels. Adequate glutathione status is particularly important for brain health and healthy ageing.
The Glutathione Index reflects how efficiently your body is recycling glutathione. It is calculated as the ratio of reduced or fully loaded glutathione to oxidised or spent glutathione. This ratio gives a meaningful picture of your antioxidant resilience rather than just a single snapshot level. A higher index suggests your cells are better equipped to handle oxidative stress.
Over the past year, our laboratory partners have analysed data from more than 600 glutathione tests alongside emerging clinical research. This larger dataset has given a clearer picture of how glutathione behaves in real world populations, particularly under conditions of oxidative and inflammatory stress.
As a result, we identified that the original reference ranges were too narrow and did not fully reflect the levels associated with optimal antioxidant recycling. Updating the ranges allows us to give more accurate, clinically meaningful interpretations and to better identify when antioxidant support may be beneficial.
• Red: Low glutathione recycling efficiency. May indicate higher oxidative stress and reduced antioxidant capacity.
• Orange: Below optimal recycling. The system may be under strain but is responsive to intervention.
• Yellow: Moderate efficiency. A common zone that highlights opportunity for improvement.
• Green: Optimal recycling efficiency associated with strong antioxidant protection.
Your measured glutathione score has not changed. What has changed is how that number is interpreted.
The updated reference ranges are:
• Red: below 500 µmol/L
• Orange: 500–649 µmol/L
• Yellow: 650–799 µmol/L
• Green: 800 µmol/L and above
Previously, the thresholds for these zones were lower. The new ranges are based on observed levels in people with stronger glutathione recycling efficiency.
| Red (µmol/L) | Orange (µmol/L) | Yellow (µmol/L) | Green (µmol/L) | |
| Old | <300 | 300-399 | 400 – 499 | >500 |
| New | <500 | 500-649 | 650 – 799 | >800 |
It is important to know that your health has not suddenly worsened. Your actual blood result is exactly the same.
If you have moved into yellow or orange, this does not mean something is wrong. These zones indicate that your antioxidant system may be under pressure and could benefit from dietary and lifestyle support.
If you have moved into red, it suggests that your cells may be experiencing a higher oxidative stress load. This is a signal to prioritise antioxidant support rather than a diagnosis.
If you remain in green, this reflects glutathione recycling levels commonly seen in people with robust antioxidant resilience.
Glutathione status responds well to diet and lifestyle changes. Helpful strategies include:
• Ensuring adequate protein intake to supply amino acids such as cysteine
• Including B vitamins, especially B6 and B12, which support glutathione pathways
• Eating a wide range of colourful plant foods rich in polyphenols such as berries, olives, beetroot, and leafy greens
• Reducing exposure to smoking, excess alcohol, and environmental pollutants where possible
• Supporting sleep, stress management, and regular movement
Depending on individual needs, supplements that may support glutathione recycling include N acetylcysteine, vitamins C and E, B vitamins, selenium, zinc, magnesium, coenzyme Q10, alpha lipoic acid, and polyphenol rich extracts such as resveratrol or anthocyanins. Supplement choices should always be personalised and ideally discussed with a qualified practitioner.
Glutathione status can change over time. Retesting every 6 to 12 months can be useful to track progress, particularly if you are making dietary or lifestyle changes or using targeted supplements.
