Low dose naltrexone (LDN) is used off-label to treat a surprisingly wide range of conditions, from chronic pain and autoimmune diseases to inflammatory bowel disorders and neurological conditions like multiple sclerosis. Naltrexone itself is FDA-approved at 50 mg for alcohol and opioid use disorders, but at much lower doses (typically under 5 mg), it appears to work through entirely different biological pathways, acting as an anti-inflammatory and immune modulator rather than simply blocking opioid receptors.
How LDN Works in the Body
At standard doses, naltrexone blocks opioid receptors to curb cravings for alcohol or opioids. At low doses, it does something different. A brief, temporary blockade of opioid receptors prompts the body to compensate by producing more of its own natural painkillers (endorphins) and by increasing the number of opioid receptors available to receive them. This “rebound” effect is the most widely cited explanation for LDN’s pain-relieving properties.
But LDN also acts on a completely separate target: a receptor called TLR4, found on immune cells in the brain and spinal cord called microglia. When microglia become overactive, they pump out inflammatory chemicals and reactive oxygen species that can damage nerves and amplify pain signals. LDN suppresses this activation, reducing neuroinflammation. This dual mechanism, boosting the body’s own painkillers while simultaneously calming immune-driven inflammation, is what makes LDN relevant across so many different conditions.
Chronic Pain and Fibromyalgia
Fibromyalgia is one of the most studied applications for LDN, and the results are encouraging. In a randomized, double-blind, placebo-controlled crossover study of 31 women with fibromyalgia, 57% of patients reported benefit from LDN. A larger retrospective review found a similar pattern: among 27 patients with fibromyalgia, widespread pain, or central sensitization, 55.6% reported symptom relief. Across small-scale trials, symptom improvement has ranged from 30% to 60%.
What’s notable is the breadth of symptoms patients report improving. Beyond pain reduction, people in these studies described improvements in fatigue, brain fog, headaches, swelling, and even skin issues like rashes and acne. This makes sense given LDN’s anti-inflammatory mechanism: if overactive immune cells are driving widespread symptoms, calming them down could help on multiple fronts simultaneously.
Crohn’s Disease and Gut Inflammation
LDN has shown some of its most striking results in inflammatory bowel disease, particularly Crohn’s disease. In one study, 33% of participants in the LDN group achieved endoscopic remission, meaning visible healing of the intestinal lining, compared to just 8% in the placebo group. In a pediatric trial, 25% of patients reached full clinical remission after eight weeks, and 67% showed clinical improvement.
These numbers are significant because endoscopic remission, not just symptom relief, suggests actual tissue healing. Larger randomized trials are currently underway to confirm these findings, but the early data has generated real interest among gastroenterologists looking for additional treatment options, especially for patients with mild to moderate disease.
Multiple Sclerosis
In MS, LDN has been studied primarily for quality of life rather than disease modification. At least three clinical trials have found that LDN improves quality of life in patients with relapsing-remitting or secondary progressive MS, with significant improvements in mental health scores. Fatigue, one of the most debilitating and undertreated MS symptoms, appears particularly responsive. In long-term follow-up, patients on LDN reported that fatigue levels were stable or decreased, and their perceived quality of life held steady.
Walking ability, measured by timed 25-foot walks, also remained stable in LDN-treated patients over time (averaging around 6 seconds at both baseline and final measurement). While stability rather than improvement might sound modest, preventing decline is a meaningful outcome in a progressive disease. LDN was well tolerated over sustained periods, with no serious adverse effects recorded.
Autoimmune Thyroid Disease
Hashimoto’s thyroiditis is one of the conditions most frequently discussed in LDN patient communities, but the evidence here is weaker than for other conditions. A large study using Norwegian prescription data tracked 898 patients with hypothyroidism who started LDN, looking at whether they were able to reduce their thyroid hormone medication afterward. The result: no change. Patients on LDN continued taking the same amount of thyroid medication as before, and there was no difference between those who filled one LDN prescription and those who filled four or more.
This doesn’t completely rule out benefit, since thyroid medication dosing is only a rough proxy for how someone feels. It’s possible LDN helps with symptoms like fatigue or brain fog without changing the underlying thyroid hormone requirement. But the study found no evidence that LDN improves thyroid function itself.
Dosing and How It’s Prescribed
LDN dosing is highly individualized. One commonly used protocol starts at just 0.1 mg per day and increases by 0.1 mg every third day, gradually working up until the patient either notices improvement or reaches 6.0 mg per day without effect. At that point, the trial is typically discontinued. The effective dose for any given person appears to be idiosyncratic, with patients in studies responding at doses ranging anywhere from 0.1 to 6.0 mg per day.
Because naltrexone is only commercially available as a 50 mg tablet, LDN must be prepared by a compounding pharmacy that can create custom capsules at the precise low doses needed. This means you need a prescription from a provider willing to prescribe off-label, plus access to a compounding pharmacy. Many compounding pharmacies now ship nationwide, and the monthly cost typically falls between $30 and $60, though this varies. Insurance rarely covers LDN since it’s an off-label use.
Side Effects
LDN is generally well tolerated. In a review of clinical experience across MS patients, 71% reported no adverse effects at all. The most common side effects were vivid dreams (9.7%) and insomnia (9.7%). These sleep-related effects make sense pharmacologically, since the temporary opioid blockade and subsequent endorphin rebound happen overnight when LDN is taken at bedtime. Some providers recommend taking it in the morning if sleep disruption is persistent.
One important safety note: because LDN partially blocks opioid receptors, it should not be taken by anyone currently using opioid medications. Even at low doses, naltrexone can precipitate withdrawal symptoms in people who are opioid-dependent. This includes both prescription painkillers and medications like methadone or buprenorphine used for opioid use disorder.