What is the Selenium (Red Cell) test?

The Selenium (Red Cell) test is a blood test that measures selenium concentration within red blood cells rather than in serum. Because red blood cells reflect mineral uptake over their lifespan, this test provides a longer-term and more stable assessment of selenium status.

Selenium is an essential trace element involved in antioxidant defence, immune function, thyroid hormone metabolism, and cellular protection. Red cell testing is particularly useful when assessing chronic deficiency or monitoring nutritional optimisation.

Clinically, this test is preferred over serum selenium when a more accurate picture of tissue selenium levels is required.

Why do I need a Selenium (Red Cell) test?

Selenium deficiency can develop due to poor dietary intake, restrictive diets, digestive or absorption disorders, or long-term illness. UK soil selenium levels are relatively low, making deficiency more common than many people realise.

Because short-term dietary intake can affect serum levels, red cell testing helps avoid misleading results. This test is especially useful when investigating fatigue, immune weakness, thyroid issues, or chronic inflammation.

You may benefit from this test if you experience:

• Frequent infections or poor immune response
• Fatigue or low energy
• Thyroid dysfunction or unexplained thyroid symptoms
• Muscle weakness
• Poor recovery from illness
• Restrictive or plant-based diets
• Long-term digestive or absorption issues

Benefits of the Selenium (Red Cell) test

1. Assesses long-term selenium status
   Reflects tissue selenium levels rather than short-term intake.
2. More accurate than serum selenium
   Less affected by recent diet or supplementation.
3. Supports immune health assessment
   Selenium is essential for immune cell function.
4. Supports thyroid function evaluation
   Required for normal thyroid hormone metabolism.
5. Assesses antioxidant defence
   Selenium is a key component of antioxidant enzymes.
6. Useful in chronic symptoms
   Relevant for fatigue and inflammatory conditions.
7. Guides targeted supplementation
   Helps avoid unnecessary or excessive selenium intake.
8. Supports preventative health strategies
   Useful for long-term nutritional optimisation.

Step-by-step – How we offer this test

Option 1: Clinic-based blood test (UK-wide)

• Choose your nearest UK clinic
• Attend your appointment
• A clinician draws a blood sample
• Sample analysed for red cell selenium

Option 2: Home or hotel visit (+£60, UK-wide)

• A qualified phlebotomist comes to your location
• Blood sample taken at home or in your hotel
• No travel required
• Same laboratory processing and reporting

Your results explained

Low Red Cell Selenium levels

Low levels indicate selenium deficiency, suggesting inadequate long-term intake or poor absorption.

Typical UK interpretation (low):

• Below laboratory reference range

Low selenium may affect immune defence, thyroid hormone metabolism, and antioxidant capacity.

Normal Red Cell Selenium levels

Normal levels suggest adequate long-term selenium status to support immune, thyroid, and antioxidant functions.

Typical UK interpretation (normal):

• Within laboratory reference range

No action is usually required unless symptoms persist.

High Red Cell Selenium levels

High levels are uncommon and usually related to supplementation.

Typical UK interpretation (high):

• Above laboratory reference range

Persistently high levels may increase toxicity risk and should be reviewed.