An old opioid antagonist repurposed at tiny doses as an immunomodulator — widely used off-label for autoimmune conditions, chronic pain, and long-COVID recovery.
Naltrexone is an opioid antagonist FDA approved at 50 mg/day for alcohol use disorder and opioid dependence. At low doses (1.5–4.5 mg/day), it shifts to an entirely different mechanism: transient opioid receptor blockade followed by upregulation of endogenous opioids (endorphins, met-enkephalin) and modulation of TLR4-driven inflammation.
LDN is prescription-only. It’s not FDA approved at low-dose and is used off-label for autoimmune disease, chronic pain, fibromyalgia, and more recently for post-COVID chronic fatigue.
Naltrexone FDA approved at 50 mg. LDN (1.5–4.5 mg) is off-label. Prescription only; typically compounded by specialty pharmacies. Not WADA prohibited.
At low doses, naltrexone briefly (4–6 hours) blocks opioid receptors. The body’s compensatory response — upregulating endorphins and enkephalins — outlasts the blockade and is the primary therapeutic mechanism.
Blocks toll-like receptor 4 on microglia and macrophages — reducing neuroinflammation and pro-inflammatory cytokine output. This is the leading mechanism for its effects on fibromyalgia and neuroinflammatory pain conditions.
Shifts Th17/Treg balance toward regulatory tone. Explains benefits seen in autoimmune conditions like Hashimoto’s, Crohn’s, and MS.
| Condition | Evidence |
|---|---|
| Fibromyalgia | The picture changed in 2026 and not in LDN’s favour. Younger 2013 (PMID 23359310) was a small crossover trial: 28.8% pain reduction on LDN vs 18.0% on placebo (p = 0.016), 32% vs 11% responders. Its authors called this "preliminary" and asked for parallel-group trials. That trial has now been run — 98 women, 12 months (Rodríguez-Freire 2026, PMID 42385209) — and found no clinically meaningful benefit: pain fell 0.33 points on LDN versus 0.64 on placebo, between-group difference p = 0.236, with secondary outcomes "minor and inconsistent." The authors place it in "the growing body of evidence questioning its clinical utility" |
| Crohn’s disease | Weaker than "remission improvements" implies. The Cochrane review (Parker 2018, PMID 29607497) found only two studies, 46 participants total. Remission was not significantly improved (30% vs 18%, RR 1.48, 95% CI 0.42–5.24); clinical response was (83% vs 38%, RR 2.22, 95% CI 1.14–4.32). Cochrane’s verdict: "insufficient evidence to allow any firm conclusions" |
| Multiple sclerosis | Mixed but positive small trials; symptom improvement, not disease modification |
| Hashimoto’s | Anecdotal and open-label: reduced antibody titers, symptom relief |
| Chronic pain (non-fibro) | Broad off-label use; modest evidence |
| Long-COVID | The most recent systematic review (Byambasuren 2026, PMID 42463201) screened 397 records and found no randomised trials at all. Pooling four small pre-post studies (n = 155) gave moderate-to-large effects for fatigue, pain and functioning — but pre-post designs have no control for regression to the mean or natural recovery, and the authors rate certainty of evidence as low |
How to hold all this. LDN is cheap, off-patent, and unusually well tolerated — which means almost nobody is funding the large trials that would settle it, and the small positive studies get repeated far more often than the larger null ones. Where a properly powered trial has been run, in fibromyalgia, it did not confirm the early signal.
That does not make LDN useless, and its safety profile is genuinely favourable, which is a real consideration when the alternatives for these conditions are opioids or immunosuppressants. It does mean the honest framing is "plausible mechanism, tolerable drug, evidence that has not held up where it was tested properly" — not "strongest evidence base," which is what this guide said until now.
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeNot medical advice. These are prescription medications. The figures below describe established clinical practice and labelled prescribing information — they are not a recommendation, they do not account for your labs, history, or other medications, and safe use depends on monitoring a page cannot do. Work with a qualified healthcare provider.
LDN is generally very well tolerated — side effects are usually mild and transient.
If you need surgery, stop LDN at least 3 days prior so anesthesia and post-op opioids work normally.
Pre-filled with a typical Low Dose Naltrexone (LDN) setup. Edit any field — the draw updates live.
Insulin syringe — 100 units = 1 mL
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Low Dose Naltrexone (LDN) is a prescription medication. StackTrax does not sell, prescribe, or facilitate purchase of prescription drugs.
Find a clinician who can order baseline lab work, screen for contraindications, monitor your response, and adjust dosing over time. Options to consider:
Before starting, you’ll typically want:
Avoid sources that offer prescription medications without labs, medical history, or licensed-provider oversight. If a telehealth service promises a prescription after a 5-minute questionnaire, that’s a red flag.
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeNaltrexone is FDA approved at 50 mg/day for alcohol use disorder and opioid dependence. Low Dose Naltrexone (1.5–4.5 mg/day) is off-label — it has not been FDA approved at low doses for any indication. It is prescription-only and typically compounded by specialty pharmacies.
Same molecule, very different mechanism at the lower dose. At 50 mg, naltrexone blocks opioid receptors continuously to deter opioid or alcohol use. At 1.5–4.5 mg, the block is transient (4–6 hours) and the body's compensatory response — upregulating endorphins and enkephalins — outlasts the blockade and is the primary therapeutic mechanism. LDN also antagonizes TLR4 on microglia and macrophages, which is the leading mechanism for its effects on fibromyalgia and neuroinflammatory pain.
Naltrexone is only manufactured as 50 mg tablets. To get a 1.5–4.5 mg dose, a compounding pharmacy makes custom capsules or a liquid suspension. This is why LDN typically requires a specialty pharmacy rather than a standard retail chain.
LDN is used off-label for fibromyalgia (where the largest trial, 98 women over 12 months, found no clinically meaningful benefit over placebo — PMID 42385209), Crohn's disease (two small studies totalling 46 patients; Cochrane found insufficient evidence for firm conclusions), multiple sclerosis (mixed but positive small trials for symptom improvement, not disease modification), Hashimoto's (anecdotal and open-label data), chronic non-fibromyalgia pain, and long-COVID (no randomised trials exist; a 2026 review pooled four small pre-post studies and rated certainty of evidence low).
Standard titration starts at 0.5–1.5 mg/day and works up to 3.0–4.5 mg/day over 2–8 weeks. Most indications top out at 4.5 mg/day, though some protocols go to 6 mg. Taken orally as a capsule or liquid, usually in the evening (9–10 PM). Give it a fair 2–8 week trial since onset is slow for most conditions.
LDN is generally very well tolerated. The most common side effects appear in the first 1–2 weeks and are usually mild and transient: vivid dreams (very common, often diminishes), mild insomnia or sleep disturbance, headache, and GI upset. The big contraindication is concurrent opioid use — any opioid medication will precipitate withdrawal. Stop LDN at least 3 days before surgery so anesthesia and post-op opioids work normally.
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StackTrax guides cover peptides and compounds that are not FDA-approved for the uses discussed. The dosing, reconstitution, and safety information is compiled from published research and community protocols for educational purposes only.
Before using any compound mentioned here, consult a qualified healthcare provider. StackTrax does not sell, prescribe, or recommend these substances for personal use.