Selenium is an essential trace mineral that supports thyroid health, detoxification, immune balance, and antioxidant protection. But despite being needed in small amounts, a deficiency can cause surprisingly widespread effects — many of which are often misdiagnosed or overlooked.
Whether due to poor soil quality, gut absorption issues, or genetic variants, selenium deficiency is more common than most people think. Here are five subtle signs your body might be running low — and what you can do about it.
1. Fatigue That Doesn’t Improve With Rest
One of the earliest signs of selenium deficiency is persistent fatigue. Selenium is required for the production of selenoproteins like glutathione peroxidase (GPx), which protect cells from oxidative stress. When your antioxidant defense is compromised, mitochondrial function suffers — leaving you feeling depleted, even after a full night’s sleep.
2. Slow Thyroid Function (Even With “Normal” Labs)
Selenium plays a key role in converting inactive T4 hormone into active T3. Without adequate selenium, you may show symptoms of low thyroid (cold intolerance, weight gain, dry skin), even if your labs are within range. This is especially true if you have genetic SNPs in DIO2 or GPX1.
3. Frequent Viral Infections
Are you getting sick more than usual? Selenium supports the immune response by enhancing antibody production and protecting immune cells from oxidative damage. Studies have shown low selenium is associated with increased susceptibility to viral infections — including influenza, coxsackievirus, and potentially long COVID.
4. Infertility or Hormone Imbalances
Selenium deficiency can impair reproductive function in both men and women. For men, low selenium is linked to reduced sperm motility and quality. For women, it may contribute to irregular cycles or miscarriages — especially when thyroid function is involved.
5. Elevated Inflammatory Markers or Detox Issues
Low selenium can impair the body’s detox pathways by reducing glutathione activity. This may show up as elevated liver enzymes, sluggish detox, skin rashes, or sensitivity to environmental triggers. If you have elevated CRP or unexplained histamine reactions, selenium should be on your radar.
How to Know for Sure
The best way to confirm a deficiency is with a functional test like RBC selenium or a full micronutrient panel. These look at intracellular levels, which provide a more accurate view than serum testing alone.
Functional practitioners may also consider genetic testing for polymorphisms in selenium-related genes (e.g., GPX1, SEPP1, SOD2) to tailor recommendations.
Related: Selenium and Your Health: The Complete Functional Guide
If any of the signs above sound familiar, your body may be asking for a deeper look into your selenium status. Catching a deficiency early can help restore energy, immune strength, and hormonal balance — before more serious issues arise.
References
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- Moslemi MK, Tavanbakhsh S. Selenium–vitamin E supplementation in infertile men: effects on semen parameters and pregnancy rate. Int J Gen Med. 2011;4:99–104. https://doi.org/10.2147/IJGM.S16275
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- Zachara BA, Wolska K, Gromadzińska J, Wasowicz W. Selenium concentration in the whole blood and the plasma glutathione peroxidase activity in patients with acute myocardial infarction. J Trace Elem Med Biol. 2001;15(1):1–5. https://doi.org/10.1016/S0946-672X(01)80018-4
- Gromadzka G, et al. The GPX1 Pro198Leu polymorphism and its impact on antioxidant enzyme activity. Clin Biochem. 2008;41(10–11):838–843. https://doi.org/10.1016/j.clinbiochem.2008.04.010
Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before changing your supplement regimen.