Low-Dose Naltrexone: Promise for Long COVID

There are an estimated 20 million people struggling with the lingering effects of COVID-19, both from the vaccine and the virus. Debilitating fatigue, brain fog, and muscle and joint pain, along with many other symptoms, can persist for months or even years after the initial infection. While treatments remain limited, emerging research points to low-dose naltrexone (LDN) as a safe, well-tolerated option that may significantly improve these stubborn symptoms.

What Is Low-Dose Naltrexone?

Naltrexone is an FDA-approved opioid antagonist traditionally prescribed at doses of 50–150 mg per day to treat opioid and alcohol dependence. However, at much lower doses—typically 4.5 mg per day or less—naltrexone behaves very differently in the body. Rather than fully blocking opioid receptors, LDN acts as a glial modulator and immune regulator, opening the door to therapeutic benefits for inflammatory and post-viral conditions like long COVID. [1]

How LDN Works

LDN's effectiveness against long COVID symptoms stems from several complementary mechanisms:

• Opioid receptor rebound effect: LDN briefly blocks opioid receptors for just 4–6 hours. This short blockade triggers a rebound response in which the body increases production of feel-good endorphins and upregulates opioid receptors. Enhanced endorphin signaling helps regulate immune function by preventing chronic inflammation. (1)
• Immune function modulation: LDN calms an overactive immune response by blocking a receptor called Toll-like receptor 4 (TLR4) on immune cells. Doing this reduces the production of inflammatory signaling molecules. It also lowers a specific inflammatory cytokine that is often elevated in people with long COVID and linked to more severe symptoms. (3)
• Opioid growth factor (OGF) pathway: LDN temporarily blocks the opioid growth factor receptor, prompting the body to produce OGF. Higher OGF levels support healthy cell growth, tissue repair, and reduced inflammation—all critical for recovery after viral illness, including COVID-19. (3,4)
• Glial cell modulation: At low doses, naltrexone influences specialized cells that nourish and protect neurons. By doing this, they modulate and reduce brain inflammation, which can lead to the brain fog so many with long COVID experience. (2)

Together, these mechanisms position LDN as a multi-target therapy that addresses the chronic immune dysregulation and neuroinflammation that drive the persistent fatigue, brain fog, muscle and joint pain, and other long COVID symptoms.

What the Research Shows

LDN is emerging as a promising option for people struggling with long COVID symptoms like fatigue, brain fog, headaches, and disrupted sleep. A 2025 review that pooled the best available studies found that LDN often led to noticeable improvements in energy, mental clarity, and sleep quality for many patients. (1)

These findings are supported by a 2024 pilot study that followed 36 individuals with ongoing, moderate-to-severe fatigue after COVID-19 who took 4.5 mg of LDN daily along with NAD+ for 12 weeks. Fatigue scores improved significantly across both physical and mental measures. About half of the participants (52%) were considered “responders,” reporting increases in energy, daily activity, pain reduction, and emotional well-being. (2)

A Favorable Side-Effect Profile

One of the most compelling aspects of LDN therapy is its remarkably low risk of serious side effects. The most commonly reported adverse events included mild nausea, fatigue, dizziness, low mood, and insomnia. These typically occurred during the first weeks of treatment and were easily managed through simple dose adjustments-for example, switching the timing of the dose from evening to morning resolved insomnia in affected patients. Notably, no serious adverse events were attributed to LDN in any of the reviewed studies. (1,2)

References

1. Du, A., & Nguyen, A. D. K. (2025). Does Low-Dose Oral Naltrexone Alleviate Symptoms of Long COVID? A Systematic Review and Meta-Analysis. COVID, 5(12), 198. https://doi.org/10.3390/covid5120198
2. Isman, A., Nyquist, A., Strecker, B., Harinath, G., Lee, V., Zhang, X., & Zalzala, S. (2024). Low-dose naltrexone and NAD+ for the treatment of patients with persistent fatigue symptoms after COVID-19. Brain, behavior, & immunity - health, 36, 100733. https://doi.org/10.1016/j.bbih.2024.100733
3. Younger, J., Parkitny, L., & McLain, D. (2014). The use of low-dose naltrexone (LDN) as a novel anti-inflammatory treatment for chronic pain. Clinical rheumatology, 33(4), 451–459. https://doi.org/10.1007/s10067-014-2517-2
4. Cant, R., Dalgleish, A. G., & Allen, R. L. (2017). Naltrexone Inhibits IL-6 and TNFα Production in Human Immune Cell Subsets following Stimulation with Ligands for Intracellular Toll-Like Receptors. Frontiers in immunology, 8, 809. https://doi.org/10.3389/fimmu.2017.00809

Written by Brooke Lounsbury