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Low-Dose Naltrexone (LDN)

Educational Overview

Low-Dose Naltrexone (LDN): What the Research Shows

Originally published 8/14/2024 · Updated 10/6/2026

Naltrexone is a long-established medication. Researchers have also been studying it at doses far lower than the standard one, an approach commonly called low-dose naltrexone, or LDN. This article offers a general introduction: what LDN is, how scientists think it may work, what clinical research has examined, and what remains unknown.

Illustration of a brain with the title Low Dose Naltrexone
Illustration of a prescription bottle labeled low-dose naltrexone

Images are for illustration purposes only.

Important

  • FDA has approved naltrexone for alcohol dependence and for blocking the effects of opioids[3]. It has not approved low-dose naltrexone for any use.
  • Low-dose use is considered off-label and, in the published literature, still experimental[1].
  • Compounded medications are not FDA-approved and have not been evaluated by the FDA for safety, effectiveness, or quality.
  • Nothing here is medical advice, a recommendation, or a promise of results.

At a Glance

What it is Naltrexone, an opioid-receptor blocker, used at much lower doses than its FDA-approved tablet strength.
Proposed mechanism Researchers have proposed that it may act on toll-like receptor 4 (TLR4) in the brain’s immune cells, called microglia[1]. This remains a hypothesis.
Most-studied area Fibromyalgia pain. A 2025 meta-analysis pooled five randomized trials[2].
U.S. regulatory status Naltrexone is approved for other uses. Low-dose use is off-label, and compounded versions are not FDA-approved[3].

Explore the Topic

Open any section below to learn more.

What is low-dose naltrexone?
▼

Naltrexone is an opioid antagonist. At its standard 50 mg tablet strength, it is FDA-approved to treat alcohol dependence and to block the effects of opioids[3].

“Low-dose” naltrexone refers to doses far below that, generally in the range of a few milligrams per day, which are not available as a commercial product. Where it is prescribed, a licensed clinician requests a custom-prepared (compounded) formulation from a pharmacy.

How do researchers think it works?
▼

One published hypothesis is that, at low doses, naltrexone acts as an antagonist of toll-like receptor 4 on microglia, the immune cells of the central nervous system. Blocking that receptor could reduce microglial activation and the release of pro-inflammatory signaling molecules[1].

The authors of that review describe LDN as “highly experimental,” note that published trials were small with few replications, and state that no studies had directly measured inflammatory markers before and after LDN treatment in people[1].

What has been studied in people?
▼

The clearest body of clinical research is in fibromyalgia, a chronic pain condition. A 2025 systematic review and meta-analysis of five placebo-controlled randomized trials found lower pain intensity with LDN than with placebo (standardized mean difference −0.61; 95% CI −1.14 to −0.08). It found no significant difference in mechanical pain threshold. Vivid dreams were reported more often with LDN (RR 2.41; 95% CI 1.77–3.28), and no serious adverse effects were reported[2].

The authors called for additional randomized trials to strengthen the evidence base[2].

Other topics: LDN is sometimes discussed online in connection with aging, weight management, mood, sleep, and general wellness. The sources cited in this article do not establish LDN for any of those purposes, and this article does not make claims about them.

What the evidence can — and can’t — tell us
▼
What has been found What is still unknown
A proposed mechanism involving TLR4 and microglia[1]. Whether this is how LDN works in people. Human inflammatory-marker studies were lacking[1].
Pooled fibromyalgia trials favored LDN for pain intensity[2]. Trials were few and small. Long-term safety, ideal dose, and use in other conditions are not established[1][2].
Naltrexone at standard doses has a well-documented label[3]. That label does not describe low-dose use or compounded formulations.
Regulatory status
▼

Naltrexone hydrochloride tablets are FDA-approved for alcohol dependence and for the blockade of exogenously administered opioids[3]. Using naltrexone at low doses for other purposes is off-label. FDA has not approved low-dose naltrexone, and the review cited above notes there is no FDA approval for pain or inflammatory indications[1].

Compounded drugs are prepared by licensed pharmacies for individual patients. They are not FDA-approved and have not been evaluated by the FDA for safety, effectiveness, or quality.

Safety Considerations
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  • Opioid medicines: naltrexone blocks opioid receptors. People taking opioid medicines, or recently exposed to them, can experience precipitated withdrawal, which can be severe. The label advises being opioid-free for a minimum of 7 to 10 days before starting[3].
  • Liver: hepatitis and clinically significant liver dysfunction have been reported with naltrexone, with greater risk at higher doses[3]. Tell your clinician about any liver condition.
  • Reported effects: in the fibromyalgia trials, vivid dreams were the most clearly increased adverse effect[2]. At standard doses, nausea, headache, dizziness, nervousness, and fatigue are listed on the label[3].
  • Mood: the label advises monitoring for depression and suicidal thoughts[3]. Contact a clinician right away, or call or text 988 in the U.S., if you have thoughts of harming yourself.
  • Long-term safety of chronic low-dose use is unknown[1].
  • Pregnancy and breastfeeding: there is no established safety data for LDN. Discuss with a licensed clinician. Tell your clinician about all medications and supplements you take.

Our Perspective

This section is editorial. LDN is a topic of real scientific interest, but interest is not proof. If you come across it from any source, we suggest asking three questions:

  1. What exactly is in it, and who prepared it? Compounded formulations vary by pharmacy.
  2. Is it safe for me? Your medicines, especially any opioids, and your liver health matter.
  3. What does the evidence show for the intended use? Ask which study supports it and how large it was.

Have questions about LDN?

Talk with our clinical team about your questions, in person or via telemedicine.

Call (561) 214-3323

Referenced Research

1

This review proposes that low-dose naltrexone may act as an anti-inflammatory agent in the central nervous system by antagonizing toll-like receptor 4 on microglial cells. The authors stress that LDN remains highly experimental, that published trials were small with few replications, that long-term safety is unknown, and that no guidelines or FDA approval exist for pain or inflammatory uses.

Younger J, Parkitny L, McLain D. “The use of low-dose naltrexone (LDN) as a novel anti-inflammatory treatment for chronic pain.” Clinical Rheumatology, 2014;33(4):451–459. doi:10.1007/s10067-014-2517-2.

2

A systematic review and meta-analysis of five randomized controlled trials compared low-dose naltrexone with placebo in fibromyalgia. LDN reduced pain intensity more than placebo (SMD −0.61; 95% CI −1.14 to −0.08), with no significant difference in mechanical pain threshold. Vivid dreams were more common with LDN (RR 2.41; 95% CI 1.77–3.28), and no serious adverse effects were reported. The authors recommend additional randomized trials.

Nazir MH, Mehboob U, Farhan M, et al. “Efficacy and safety of low-dose naltrexone (LDN) in fibromyalgia: a systematic review and meta-analysis.” Annals of Medicine and Surgery, 2025;87:2928–2935. doi:10.1097/MS9.0000000000003203.

3

Prescribing information for naltrexone hydrochloride tablets (50 mg) lists FDA-approved indications of alcohol dependence and blockade of the effects of exogenously administered opioids. It warns of precipitated opioid withdrawal, advises a minimum of 7 to 10 days opioid-free before starting, describes hepatitis and liver dysfunction (greater at higher doses), and lists common adverse reactions including nausea, headache, dizziness, nervousness, and fatigue. It does not describe low-dose use.

“Naltrexone Hydrochloride Tablets, USP: Indications, Warnings, and Adverse Reactions” (prescribing information summary). RxList

Important Disclosures

  • This article is for educational purposes only and is not medical advice. These statements have not been evaluated by the U.S. Food and Drug Administration. Nothing on this site is intended to diagnose, treat, cure, or prevent any disease.
  • Low-dose naltrexone is not FDA-approved. Compounded medications are not FDA-approved and have not been evaluated by the FDA for safety, effectiveness, or quality.
  • Images are for illustration purposes only. Individual results vary.
  • Treatment decisions are made solely by an independent, licensed clinician after an individualized evaluation, and a doctor-patient relationship is established only after a qualifying consultation.

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