Low dose naltrexone (LDN) is a repurposed version of naltrexone, a medication normally prescribed at 50 mg daily for opioid and alcohol addiction. At much smaller doses, typically between 0.1 and 4.5 mg per day, it appears to work through an entirely different pathway: reducing inflammation in the nervous system. This anti-inflammatory effect has made it a growing area of interest for chronic pain, autoimmune conditions, and inflammatory bowel disease.
How LDN Works in the Body
The most well-supported explanation for how LDN works centers on its ability to calm immune cells in the brain and spinal cord called microglia. When these cells become overactive, they drive chronic inflammation and amplify pain signals. LDN binds to a receptor on microglia called Toll-like receptor 4 (TLR-4) and blocks it, which dials down the inflammatory chemicals these cells release. Researchers refer to this as “glial attenuation,” essentially quieting an immune response that has become stuck in overdrive.
For years, a popular theory held that LDN works by briefly blocking opioid receptors, which then triggers the body to produce more endorphins (its natural painkillers) in a rebound effect. This idea was intuitive and widely repeated, but a study published in eNeuro tested it directly in mice and found no evidence to support it. LDN did not change opioid receptor sensitivity, did not increase production of the endorphin precursor, and did not raise endorphin levels in the blood. The actual mechanism appears to be the TLR-4 pathway and immune modulation rather than an endorphin boost.
Conditions LDN Is Used For
Chronic Pain
LDN has been studied most extensively for chronic pain conditions, particularly fibromyalgia and complex regional pain syndrome. Because it targets neuroinflammation rather than blocking pain signals the way traditional painkillers do, it works through a fundamentally different approach. Effective doses for chronic pain generally fall between 1.0 and 4.5 mg per day, though an observational study found that most patients stabilized at 2 mg or less, suggesting the commonly cited 4.5 mg target may be higher than many people need.
Crohn’s Disease
Some of the most striking data for LDN comes from inflammatory bowel disease, particularly Crohn’s disease. In one open-label pilot study of 17 patients, 89% experienced a clinical response and 67% achieved full remission after 12 weeks of LDN therapy. A subsequent randomized, placebo-controlled trial in 34 patients with IBD found an 88% response rate in the LDN group compared to 40% with placebo. Endoscopic remission, meaning visible healing of the gut lining, occurred in 33% of LDN patients versus 8% on placebo. These are small studies, and larger trials are underway, but the early results are notable.
Multiple Sclerosis
A placebo-controlled crossover trial of 80 people with multiple sclerosis tested 4.5 mg of nightly LDN for eight weeks. LDN did not change physical disability scores, but it significantly improved mental health quality of life. Participants reported better overall mental health, reduced pain effects, and improvements in perceived cognitive function. The mental health composite score improved by 3.3 points, and the mental health inventory improved by 6 points compared to placebo.
Dosing and How to Get It
LDN is not FDA-approved for any of these uses. Naltrexone is only approved at 50 mg for addiction treatment, so getting LDN requires a prescription that a compounding pharmacy fills at the lower dose. Compounded drugs are not subject to the same FDA verification for safety, effectiveness, or quality as commercially manufactured medications, though outsourcing facilities must follow good manufacturing practice standards.
Dosing is highly individual. The typical approach starts low, sometimes as low as 0.1 mg per day, and increases gradually. One common protocol raises the dose by 0.1 mg every three days until the patient finds relief or reaches a ceiling of around 5 to 6 mg. Many clinicians start at 1.5 mg for a month, then move to 3 mg, reaching a target of 4.5 mg after about two months. If no improvement occurs by 6 mg, the trial is usually stopped. An observational study found that effective doses varied widely from patient to patient, reinforcing that there is no single correct dose.
How Long It Takes to Work
LDN is not a fast-acting medication. Most patients who respond notice symptom relief after one to three months of consistent use. Part of this delay is the titration process itself, since reaching the target dose can take eight weeks. The Crohn’s disease trials measured outcomes at 12 weeks, and the MS trial ran for eight weeks, which gives a reasonable picture of the timeline. If you start LDN, expect a gradual process rather than immediate results.
Side Effects
LDN is generally well tolerated. The MS trial reported no serious adverse events, and reviews across multiple studies describe a mild side effect profile. The most commonly reported effects are vivid dreams, mild headaches, and temporary sleep disturbances, particularly in the first few weeks.
Vivid dreaming is the side effect people ask about most. LDN appears to influence neurotransmitter activity, particularly serotonin and dopamine, which are both associated with dream intensity. Because LDN is typically taken at bedtime, it can increase the vividness and memorability of dreams during REM sleep. For most people this is more noticeable than bothersome, and it often settles down over time. Some clinicians interpret increased dreaming as a sign that the medication is having a neurological effect.
Who Should Not Take LDN
The most important restriction involves opioid medications. Because naltrexone blocks opioid receptors, even at low doses, taking LDN while on opioid painkillers can trigger withdrawal symptoms. At very low and ultra-low doses (below 1 mg), some research suggests concurrent opioid use may be manageable with careful dose adjustment, but this requires close medical supervision. The primary safety concern at standard naltrexone doses (50 mg and above) is liver toxicity, but this has not been a reported issue at the low doses used in LDN therapy.