Low-dose naltrexone, or LDN, is the same drug used at 50 mg to treat opioid and alcohol dependence, taken instead at roughly a tenth of that, about 1 to 4.5 mg. At that low dose the proposed action is different: a brief, partial block of opioid receptors, followed by a compensatory rise in the body's own endorphins, together with a separate calming effect on the immune cells of the nervous system. The clearest research signals are in fibromyalgia, Crohn's disease and the symptoms of multiple sclerosis, and in a few of these the small trials are promising.
That evidence is smaller than the online reputation suggests: most of it comes from small, often single-site studies, the drug is usually supplied by a compounding pharmacy, and it is prescribed off-label. This page is education about what has and has not been shown, not a recommendation to obtain or take it, and it gives no protocol.
Findings & Outcomes
What It Is
Naltrexone is a long-established prescription drug that blocks opioid receptors. At 50 mg a day it is approved to treat opioid and alcohol dependence, where a full, steady block is the goal. Low-dose naltrexone is the same molecule taken at roughly 1 to 4.5 mg, about a tenth of that amount, for a different purpose. At the low dose the receptor block is brief and partial. The interest is in two knock-on effects: the body's response to that short block, and a separate anti-inflammatory action.
None of the uses discussed here are approved. There is no 4.5 mg naltrexone product on a pharmacy shelf, so LDN is prescribed off-label and usually made up to order by a compounding pharmacy. That shapes both how to read the evidence and how to weigh the safety, which is why this page treats LDN as a clinician-prescribed off-label practice under study. The range above is what defines the category; this page gives no dosing protocol or schedule to follow.
Anatomy
1The rebound idea
At a low dose taken at night, naltrexone briefly and partly blocks opioid receptors for a few hours. The proposed effect is that the body responds to the block as if its own opioids were short and increases their production, so endorphin and enkephalin activity rises after the drug has cleared. This endorphin rebound is the mechanism most often offered for the pain and wellbeing effects people report, and it is still a hypothesis, not a confirmed pathway.
2The immune-cell effect
Separately, naltrexone and its relative naloxone act on a receptor called TLR4 that sits on microglia, the immune cells of the brain and spinal cord. Quieting TLR4 signaling on activated microglia lowers the release of inflammatory messengers. This glial, anti-inflammatory action is the leading explanation for why LDN has been studied in conditions driven by inflammation, not only in pain.
3Why the low dose matters
The two proposed effects are thought to depend on the dose being low and the block being transient. A full, continuous block at 50 mg would not leave the brief gap that is thought to trigger the rebound, and it is used precisely to keep opioid receptors blocked. The low dose is what separates this use from the addiction use, and it is also why the drug has to be compounded instead of bought as a standard tablet.
How It Works
Two mechanisms are proposed, and both are still best described as hypotheses supported by laboratory work, not settled human pathways. The first is the endorphin rebound. A low dose of naltrexone occupies opioid receptors briefly, and the body is thought to compensate by increasing production of its own opioid peptides, the endorphins and enkephalins, so that after the drug clears there is more opioid signaling than before. Because these internal opioids influence pain, mood and immune regulation, a sustained rise in them is the mechanism most often given for the symptom relief people describe.
The second mechanism is anti-inflammatory and does not run through the classic opioid receptors. Naltrexone antagonizes TLR4, a receptor on microglia and other immune cells, and activated microglia are a source of the inflammatory signaling that amplifies chronic pain and is present in inflammatory bowel and neurological disease. Turning that signaling down is the proposed route for the effects seen in Crohn's disease and multiple sclerosis. Reviews of the mechanism treat both pathways as plausible and partly supported, while noting that the human trials measure symptoms and outcomes rather than confirming the pathway directly.
What Changed
The version of LDN that circulates online often presents it as a cheap, near-miraculous fix suppressed by a drug industry with no reason to study an old, unpatentable molecule. That framing overstates an early body of evidence and understates how much of it rests on small studies.
What holds up is that a low dose of an old, inexpensive, generally well-tolerated drug produces measurable effects in a few specific conditions:
- In fibromyalgia, a small randomized trial and an earlier pilot show a reduction in pain.
- In Crohn's disease, small trials show clinical response and endoscopic improvement.
- In multiple sclerosis, trials show gains in some quality-of-life measures.
These are findings in serious conditions where existing options are imperfect, and the proposed mechanisms give a coherent reason to expect them, which is why researchers continue to study LDN.
The part that gets stretched is the leap from these signals to a proven treatment. Most of the trials are small, several come from a single site or a single research group, and the multiple sclerosis results are mixed, with the gains appearing in wellbeing measures rather than in the disease itself. The drug is supplied by compounding pharmacies, which vary, and it is prescribed off-label for all of these uses. The measured reading is that LDN carries a promising early signal in a handful of conditions, held back by the small size of the evidence, not by suppression, and that it is a clinician-prescribed off-label option, not an established therapy.
Where The Research Stands
Fibromyalgia
This is the best-studied use and the one with the cleanest signal. A single-blind pilot in ten women with fibromyalgia reported more than a 30% reduction in symptoms on low-dose naltrexone compared with placebo. A later double-blind, placebo-controlled crossover trial in thirty-one women found a larger reduction in pain on LDN than on placebo, about 29% against 18%, with 32% of participants meeting a meaningful response against 11% on placebo. Both trials were small, both came from the same research group at a single center, and both were conducted in women, which fits the condition and leaves the effect in men untested. A consistent signal and a plausible mechanism place fibromyalgia first among the LDN findings, and it is still early evidence.
Crohn's Disease
The inflammatory bowel evidence is the other relatively strong area. An open-label pilot in seventeen adults with active Crohn's disease reported that 89% improved and 67% reached remission by symptom score, though with everyone knowing they took the drug there was no placebo comparison. A follow-up randomized, placebo-controlled trial in forty adults found that more people on LDN showed endoscopic improvement of the bowel lining, 78% against 28% on placebo, a harder endpoint than symptoms alone. A separate pediatric trial, blinded and placebo-controlled before an open-label phase, found LDN was tolerated in children with Crohn's disease. These are small, largely single-site trials from one group whose lead investigators hold a patent on naltrexone for inflammatory bowel disease, so the finding is promising and not yet confirmed by larger independent work.
Multiple Sclerosis
The multiple sclerosis evidence is mixed, and it is mostly about quality of life, not the disease itself. An eight-week crossover trial improved mental-health quality-of-life scores but not physical ones, and a longer crossover trial found no significant effect on most quality-of-life measures. Neither was designed to show, nor did it show, a change in disability or disease progression. In multiple sclerosis the benefit is modest and inconsistent, limited to some symptom and wellbeing measures, and the trials were small.
The Shape Of The Evidence
One pattern runs through all of it:
- The trials are small, often a few dozen participants.
- Several of the strongest come from a single site or a single research group.
- Independent replication at larger scale is mostly absent.
The drug itself is supplied by compounding pharmacies, so the exact preparation can vary between sources. None of this makes the signals false, and the consistency across conditions with a shared inflammatory thread is part of why the interest is warranted.
The plain status is an early, promising body of evidence, not a proven one: LDN is used off-label on a clinician's judgment, not on the strength of large trials.
This page describes that evidence and gives no dosing protocol or schedule to follow.
The Research & Studies
Everything here is based on the research we have collected and checked, sorted into groups and ordered with the strongest evidence first. Click any claim to open the studies behind it.
How it works
Proposed: the brief opioid block rebounds into more of the body's own endorphins
The low dose briefly blocks opioid receptors, and the body is thought to answer by making more of its own endorphins, so there is more opioid signaling once the drug wears off. This rebound is the leading explanation for the effects people report, and it is still a hypothesis.
At roughly 1 to 4.5 mg, naltrexone briefly and partly blocks opioid receptors; the proposed response is a compensatory rise in endogenous opioid peptides (endorphins and enkephalins) after the drug clears, which is offered as the mechanism for the analgesic and wellbeing effects reported. The pathway is inferred rather than directly confirmed in the human trials. The endorphin-rebound pathway is inferred from pharmacology and animal work; the clinical trials measure symptoms rather than confirming a sustained rise in endogenous opioids in these patients.
The studies · 2
Younger et al., The use of low-dose naltrexone (LDN) as a novel anti-inflammatory treatment for chronic pain · Clin Rheumatol 2014;33(4):451-459
Toljan and Vrooman, Low-Dose Naltrexone (LDN): Review of Therapeutic Utilization · Med Sci (Basel) 2018;6(4):82
Counts once: this finding and 1 other here come from the same source, so they are one body of evidence, not separate confirmations.
Proposed: naltrexone quiets TLR4 on microglia to lower nervous-system inflammation
Separately from opioids, naltrexone calms a receptor called TLR4 on the immune cells of the nervous system, which lowers inflammatory signaling. This is the leading reason it has been studied in conditions driven by inflammation, not just in pain.
Naltrexone antagonizes Toll-like receptor 4 (TLR4) on microglia and other immune cells; quieting TLR4 signaling on activated microglia lowers release of pro-inflammatory mediators, which is the proposed route for effects in inflammation-driven conditions and is distinct from classic opioid-receptor action. The glial anti-inflammatory effect is established in laboratory models; its contribution to the clinical results in people has not been measured directly in the trials.
The study · 1
Younger et al., The use of low-dose naltrexone (LDN) as a novel anti-inflammatory treatment for chronic pain · Clin Rheumatol 2014;33(4):451-459
Counts once: this finding and 1 other here come from the same source, so they are one body of evidence, not separate confirmations.
Pain
Fibromyalgia pain fell about 29% vs 18% on placebo in a 31-woman RCT
In a randomized trial of 31 women, the low dose reduced pain more than placebo, by about 29% against 18%. A consistent but small signal in the best-studied use.
In a double-blind, placebo-controlled, counterbalanced crossover trial of 31 women with fibromyalgia, low-dose naltrexone reduced daily pain more than placebo (about 29% versus 18%, P=0.016), and 32% met a clinically meaningful response against 11% on placebo. 31 participants from a single center and one research group, without larger independent replication.
Who this may not transfer to:Conducted entirely in women; the effect in men with fibromyalgia was not tested, so it is unknown rather than assumed to transfer.
The study · 1
Younger et al., Low-dose naltrexone for the treatment of fibromyalgia: findings of a small, randomized, double-blind, placebo-controlled, counterbalanced, crossover trial · Arthritis Rheum 2013;65(2):529-538
Fibromyalgia symptoms fell more than 30% over placebo in a 10-woman pilot
In a small early study of 10 women, the low dose cut fibromyalgia symptoms by more than 30% compared with placebo. It is an encouraging first signal from a very small, single-center study.
In a single-blind, placebo-controlled crossover pilot of 10 women with fibromyalgia, low-dose naltrexone (4.5 mg) reduced self-reported symptoms by more than 30% relative to placebo. Ten participants, single-blind, single site, one research group; a pilot that motivates a larger trial rather than establishing the effect.
Who this may not transfer to:Studied only in women, which fits a condition diagnosed far more often in women, but the effect in men was not tested and is unknown rather than assumed similar.
The study · 1
Younger and Mackey, Fibromyalgia symptoms are reduced by low-dose naltrexone: a pilot study · Pain Med 2009;10(4):663-672
Digestion
Bowel-lining healing in 78% vs 28% on placebo in a 40-adult Crohn's RCT
In a randomized trial of 40 adults, more people on the low dose showed healing of the bowel lining seen on endoscopy than on placebo, 78% against 28%. Healing seen on camera is a stronger sign than feeling better.
In a randomized, placebo-controlled trial of 40 adults with active Crohn's disease, more participants on low-dose naltrexone showed endoscopic improvement of the bowel lining than on placebo (78% versus 28%, p=0.008), a mucosal endpoint harder than symptom scores alone. The primary clinical endpoint, a 70-point drop in the disease-activity index, was met by 88% on the drug against 40% on placebo. 40 participants at a single site from one research group, whose lead investigators hold a patent on naltrexone for inflammatory bowel disease; a promising mucosal result that awaits larger independent confirmation.
The studies · 2
Smith et al., Therapy with the opioid antagonist naltrexone promotes mucosal healing in active Crohn's disease: a randomized placebo-controlled trial · Dig Dis Sci 2011;56(7):2088-2097
Smith et al., Safety and tolerability of low-dose naltrexone therapy in children with moderate to severe Crohn's disease: a pilot study · J Clin Gastroenterol 2013;47(4):339-345
Crohn's response in 89% and remission in 67% of a 17-adult open-label pilot
In an early open-label study of 17 adults with active Crohn's disease, 89% improved and 67% reached remission by symptom score. Open-label means everyone knew they were taking the drug, so the placebo effect is not controlled.
In an open-label pilot of 17 adults with active Crohn's disease, 89% responded to low-dose naltrexone and 67% reached remission by the Crohn's Disease Activity Index over twelve weeks. With no control group, expectation and natural fluctuation are not separated out. 17 participants, open-label with no placebo control, so improvement cannot be separated from expectation or natural fluctuation.
The study · 1
Smith et al., Low-dose naltrexone therapy improves active Crohn's disease · Am J Gastroenterol 2007;102(4):820-828
Autoimmune Neuro
Mixed quality-of-life results in MS, with no change in disability
In multiple sclerosis the results are mixed and mostly about wellbeing rather than the disease itself. One short trial improved some mental-health quality-of-life scores; a longer one found little effect. Neither changed disability or the course of the disease.
Randomized crossover trials in multiple sclerosis report mixed results: an eight-week trial improved mental-health quality-of-life scores but not physical ones, while a longer crossover trial found no significant effect on most quality-of-life measures. Neither was designed to alter, nor showed a change in, disability or disease progression. Small crossover trials with inconsistent findings, limited to quality-of-life measures rather than disability progression, so this is a modest and uncertain symptom signal, not a disease-modifying effect.
The studies · 2
Cree et al., Pilot trial of low-dose naltrexone and quality of life in multiple sclerosis · Ann Neurol 2010;68(2):145-150
Sharafaddinzadeh et al., The effect of low-dose naltrexone on quality of life of patients with multiple sclerosis: a randomized placebo-controlled trial · Mult Scler 2010;16(8):964-969
Go Deeper
- Fibromyalgia: the condition with the clearest LDN signal, and the full picture of what helps and what does not.
- Metformin: another old, inexpensive drug studied off-label beyond its approved use, and how to read that kind of evidence.
- Peptides: a neighboring area where a few tested compounds sit alongside a large, loosely regulated market.
- Ivermectin: another repurposed drug where the popular story and the trial evidence have to be kept apart.
The Chinese Medicine View
Low-dose naltrexone is a modern pharmaceutical used in a modern way, so there is no classical Chinese entry for it. No historical text assigns it a channel, a temperature or a flavor, and no traditional formula contains it. What follows places it against the tradition as a lens, not as evidence, and it borrows no classical claim, because none exists. Nothing here suggests any herb or formula reproduces what the drug does.
The territory LDN is studied in is one Chinese medicine has long reasoned about. Fibromyalgia, with its shifting widespread pain and fatigue, is often read through patterns of Liver Qi stagnation, Blood stasis and underlying deficiency, and the chronic bowel inflammation of Crohn's disease through Spleen and Stomach weakness with Damp-Heat. In each case the tradition treats the whole pattern in the person, not a single receptor, and it holds a caution that applies here: relief of a symptom is not the same as restoring the function beneath it, and a powerful intervention aimed narrowly can leave the root pattern untouched or, if the person is depleted, can be poorly tolerated. That framing would ask not only whether a drug reduces pain but whether the person has the reserves to benefit, and it would not read symptom relief as a cure.
The limit is that this is a way of relating a modern drug to a framework the tradition reasons about, not a claim that Chinese medicine endorses or explains LDN. The classical concepts belong to the tradition as it uses them, and the evidence for the drug rests on its own trials, which are small.
Cautions
Everything to be aware of is here, in one place. This practice suits most healthy people; a few situations call for real care.
Generally well tolerated at low dose, but it blocks opioid painkillers
Across the trials, low-dose naltrexone is generally well tolerated, with vivid dreams and sleep disturbance the most commonly reported effects and few serious adverse events. It is contraindicated with opioid medication, because it blocks opioid receptors and can precipitate withdrawal, and it carries caution in significant liver disease. Tolerability data come from small trials of limited duration; the compounded, off-label supply falls outside the checks that apply to an approved product.Toljan and Vrooman, Low-Dose Naltrexone (LDN): Review of Therapeutic Utilization
It cannot be combined with opioid medication
Naltrexone blocks opioid receptors, so taking it while using opioid pain medicine can block the pain relief and can precipitate withdrawal in someone dependent on opioids. Anyone taking opioids, or facing surgery where opioids may be needed, must sort this out with a prescriber first. It is why LDN is a prescriber's decision rather than a self-directed one.
It is prescribed off-label and compounded
There is no approved low-dose naltrexone product, so it is prescribed off-label and made up by a compounding pharmacy, whose preparations vary. That places it outside the standard checks that apply to an approved medicine, which is a further reason it belongs with a prescriber who can choose a reliable source and follow up.
Vivid dreams and sleep effects
The most commonly reported side effect is vivid or unusual dreams and disturbed sleep, especially in the first weeks and when the drug is taken at night. For most people in the trials this was mild and settled, but it is the effect people notice most, and the timing of the dose is something a prescriber adjusts.
It is not a proven treatment for these conditions
The evidence in fibromyalgia, Crohn's disease and multiple sclerosis comes from small, mostly single-site trials, and LDN is not approved for any of them. It should not replace treatment that is established for a serious condition, and any decision to try it belongs in a conversation with a clinician who knows the whole picture.
Liver and other medicines
Naltrexone is processed by the liver and carries cautions in significant liver disease, and its interaction with other drugs, above all opioids, needs a prescriber who has the full medication list. Self-management from an online source skips exactly the checks that make its use reasonable.
Start slow, be smart, read the research, and consult a professional if you have any concerns. This is here to inform your choice, not make it for you.
Common Questions
What is the difference between low-dose naltrexone and regular naltrexone?
It is the same drug at very different doses for different purposes. At 50 mg a day, naltrexone is approved to treat opioid and alcohol dependence by blocking opioid receptors steadily. At roughly 1 to 4.5 mg, about a tenth of that, the block is brief and partial, and the interest is in a rebound in the body's own endorphins and in a separate anti-inflammatory effect on immune cells. The low-dose use is off-label and is not approved for any condition.
Does low-dose naltrexone actually work for fibromyalgia?
The evidence is promising and small. A pilot study and a later randomized crossover trial, both in women and both from one research group, found more pain reduction on LDN than on placebo, with the randomized trial showing around a 29% reduction against about 18% on placebo. That is a consistent signal in the best-studied use, but the trials were small and single-site, so it is early evidence, not a settled result, and it has not been tested in men.
Is low-dose naltrexone safe?
At the low dose it is generally well tolerated in the trials, with vivid dreams and sleep disturbance the most common effects and few serious problems reported. The critical exception is that it cannot be taken with opioid pain medicine, because it blocks opioids and can trigger withdrawal. It also carries cautions in significant liver disease. Because it is prescribed off-label and compounded, its use belongs with a clinician rather than being self-directed.
Why is low-dose naltrexone not approved if the results look good?
Partly because the evidence, while promising, is still small and mostly from single-site trials, and partly because naltrexone is an old, inexpensive drug with little commercial incentive for a company to fund the large trials that approval requires. The signals in fibromyalgia and Crohn's disease justify further study. They are not yet the large, independently replicated evidence that would move LDN from an off-label option to an approved treatment.
Explore Related
Other pages this one connects to, by the evidence they share, the outcomes they touch, and the ground they cover.
All 11 sources on this page independently checked and cross-referenced.
Thomas Dehli, Founder & Editor, Sacred Lotus
Sacred Lotus has published Chinese medicine reference material since 2001. Integrative pages are held to the same standard as the herb and formula library: cite the source, grade the claim at its real strength, and say where the research has not looked. This page is educational and it is not medical advice. Last reviewed and updated August 9, 2026.
Evidence strength
How confidently the research supports a claim. Strength describes the evidence, not our endorsement.