Low-Dose Naltrexone for Fibromyalgia and ME/CFS

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Low-dose naltrexone therapy helps to relieve pain and fatigue associated with fibromyalgia and chronic fatigue syndrome.

Naltrexone is a medication that has been used to treat alcohol dependence and opioid-use disorder for more than 30 years. More recently, researchers found low doses of naltrexone—about 1/30th the standard dose—may be useful for other conditions.

This article discusses low-dose naltrexone benefits and uses related to fibromyalgia and chronic fatigue syndrome. It also explains the side effect of LDN therapy and what to avoid when taking naltrexone.

Medication being poured into hand.
Jack Hollingsworth / Getty Images

How Does Low-Dose Naltrexone Work?

At a normal dose of 50 to 100 milligrams (mg), naltrexone blocks the effects of opioid pain relievers and alcohol. It works by binding to opioid and endorphin receptors, preventing the feel-good molecules in alcohol and opioids from attaching.

Researchers are not entirely sure how lower doses of naltrexone work to relieve fibromyalgia, chronic fatigue syndrome, and potentially other conditions. Proposed pathways include:

  • LDN blocks certain proteins that cause symptoms of fibromyalgia and chronic fatigue syndrome in the nervous system, which is the primary controlling and communicating system in the body
  • LDN works as an anti-inflammatory, which reduces inflammation or swelling in the nervous system
  • LDN may help keep the immune system, or what protects the body from harmful invaders, well-balanced, which may be why it tends to help people with immune system-related illnesses
  • LDN temporarily blocks receptors associated with pain and triggers the release of endorphins, the body's natural painkillers

Low-Dose Naltrexone Uses

At very low doses, naltrexone may help people with fibromyalgia, chronic fatigue syndrome, and other conditions. Here is a closer look at low-dose naltrexone benefits and uses.


Fibromyalgia is a chronic condition characterized by widespread pain, fatigue, sleep disturbancecognitive impairmentdepressionenvironmental sensitivities, and digestive symptoms.

Small studies have shown that individuals taking LDN to treat fibromyalgia showed as much as a 30% decline in symptoms compared to those given a fake treatment.

Results tended to be best in those who had an inflammatory response, which is when the immune system responds to injury or illness. The drug was also well tolerated, with minimal side effects.

LDN is not FDA-approved for fibromyalgia but is sometimes prescribed for off-label use.

Chronic Fatigue Syndrome

Chronic fatigue syndrome is also known as myalgic encephalomyelitis. The condition involves deep fatigue, unrefreshing sleep, exercise intolerance, and neurological issues referred to as “brain fog.” Every person with chronic fatigue syndrome has a unique set of symptoms and degree of intensity.

LDN has not been studied in a clinical trial for chronic fatigue syndrome, but it is sometimes prescribed off-label. There is growing evidence that some individuals have seen a reduction in their symptoms while using LDN.

Research suggests that individuals with chronic fatigue syndrome may have neuroinflammation, which is an inflammatory response in the brain or spinal cord. Because LDN may have an impact on inflammation in the nervous system, it's understandable why this may be a helpful treatment for some.

Other Use for Low-Dose Naltrexone

Research shows some promise for low-dose naltrexone in treating these other conditions:


Low-dose naltrexone is prescribed off-label as a treatment for fibromyalgia, chronic fatigue syndrome/myalgic encephalomyelitis, diabetic neuropathy, multiple sclerosis, Parkinson's disease, and other conditions. However, there is limited research to show it is effective.

What Dosage Is Low-Dose Naltrexone?

For use in treating fibromyalgia or chronic fatigue syndrome, naltrexone is generally given in doses of 4.5 mg or less. Typically, you'll start at 1.5 mg, work up to 3 mg, then increase to 4.5 mg.

Keep in mind that higher doses of naltrexone have not been shown to have the same symptom-reducing effects for fibromyalgia or chronic fatigue syndrome.

LDN Side Effects

While LDN appears to be well-tolerated, known side effects of naltrexone include dizziness, headache, difficulty sleeping (insomnia), vivid dreams, nausea, vomiting, decreased appetite, joint pain, muscle cramps, tooth pain, and anxiety. Pain and swelling at the injection site may also occur if naltrexone is injected rather than taken as a pill.

In rare instances, there can be severe side effects such as increased blood pressure or heart rate, confusion, depression, and allergic reactions. Contact your healthcare provider right away if you experience any of these.

People with kidney disease or liver disease may need to speak with their doctor before starting LDN. Those who are pregnant or breastfeeding should also speak with their doctor before starting this medication.


Even at low doses, naltrexone should not be taken with certain medications or alcohol. Do not take LDN with opiate painkillers such as Ultram (tramadol) and OxyContin (oxycodone).

Naltrexone may interact with chemotherapy drugs and the following medications (known as CYP450 substrates):

  • Norvasc (amlodipine)
  • Abilify (aripiprazole)
  • Lipitor (atorvastatin)
  • BuSpar (buspirone)
  • Valium (diazepam)
  • Erythrocin (erythromycin)
  • Proscar (finasteride) 
  • Prometrium (progesterone)
  • Viagra (sildenafil)
  • Zocor (simvastatin)
  • Aveed (testosterone)
  • Coumadin (R-warfarin)


Researchers aren't sure exactly how LDN works when it comes to fibromyalgia and chronic fatigue syndrome. Some believe it may act as an anti-inflammatory agent, help balance the immune system, or trigger the release of endorphins.

In research and case studies, LDN has been shown to help decrease symptoms of both fibromyalgia and chronic fatigue syndrome with minimal side effects.

A Word From Verywell

If you're interested in trying LDN, talk to your healthcare provider about the possible pros and cons. Not all healthcare providers will prescribe LDN for people with fibromyalgia or chronic fatigue syndrome, as it's still considered an emerging treatment.

Frequently Asked Questions

  • Why is only a low dose of naltrexone prescribed for fibromyalgia?

    At high doses, naltrexone has a different effect on the body's systems.

  • Is it safe to take low-dose naltrexone for long periods of time?

    Yes. Research shows that the drug seems safe for long-term use. As long as naltrexone benefits you, you can take it on an ongoing basis.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Adrienne Dellwo
Adrienne Dellwo is an experienced journalist who was diagnosed with fibromyalgia and has written extensively on the topic.