Naltrexone was approved decades ago, at 50 mg, to treat opioid and alcohol dependence. At a tiny fraction of that dose, typically 1.5 to 4.5 mg, it behaves like an entirely different medication.
Low-dose naltrexone, or LDN, has become one of the more interesting tools in functional medicine for chronic pain, inflammation, and immune problems. This article looks at the specific conditions where it shows promise and what the evidence actually says.
How LDN Works
At low doses taken at night, naltrexone briefly blocks your opioid receptors. Your body responds by increasing production of endorphins, your natural pain-relieving and immune-regulating compounds.
LDN also calms microglia, the immune cells of the brain and spinal cord. When microglia are stuck in overdrive they drive neuroinflammation, and that is thought to be central to conditions like fibromyalgia. This mechanism is different from how anti-inflammatory drugs work, which is why LDN sometimes helps where they have not.
Fibromyalgia
This is where the evidence is strongest. Several small trials show meaningful reductions in pain and improved quality of life.
The studies are small, which is an honest limitation. But fibromyalgia has few good options, most carry significant side effects, and LDN is inexpensive and well tolerated. For many patients that balance is worth a trial.
Autoimmune Conditions
Patients with Hashimoto's thyroiditis, Crohn's disease, and other autoimmune conditions often report fewer symptoms and better day-to-day function.
The appeal here is mechanism as much as effect. Most autoimmune treatments work by suppressing the immune system, which helps the disease but raises infection risk. LDN appears to modulate immune activity rather than suppress it.
LDN is usually added alongside existing treatment, not used instead of it. Nobody should stop a disease-modifying medication to try LDN.
Chronic Pain and Nerve Pain
Patients with chronic low back pain, diabetic neuropathy, and other nerve pain conditions often report improvement, particularly where pain has become centralized, meaning the nervous system itself has become over-sensitized.
This is the kind of pain that does not respond well to anti-inflammatories because the problem is no longer in the tissue. It is in the signaling.
Other Reported Uses
- Chronic fatigue and long COVID. Early reports are encouraging, evidence is still thin.
- Inflammatory bowel disease. Small studies in Crohn's have shown improvement.
- Multiple sclerosis. Often reported to help fatigue and quality of life rather than the disease course.
- Complex regional pain syndrome. Case reports and small series.
The honest summary: promising, under-studied, and worth trying in the right patient because the downside is low.
Why the Research Is Limited
Naltrexone has been off patent for years. There is no company with a financial reason to fund large trials of a cheap generic used at an unapproved dose.
That is a commercial problem, not a scientific verdict. It does mean LDN is prescribed off-label, and you deserve to know that up front.
Who It Is Not For
LDN blocks opioid medications. If you take opioids for pain, LDN is not an option while you do.
It also needs care in significant liver disease, and it is not appropriate in pregnancy without a specific discussion. Tell us about everything you take before starting.
What a Trial Looks Like
We start at 0.5 to 1.5 mg at bedtime and increase slowly over several weeks. The most common early side effects are vivid dreams and disrupted sleep, which usually settle within a couple of weeks or resolve by moving the dose to the morning.
Give it about three months at a good dose before judging it. Some people respond in weeks, others take longer. If there is no benefit by then, we stop rather than continue indefinitely.
What Patients Actually Report
The improvements people describe are often not the ones they expected. Pain scores may drop modestly while sleep improves substantially, or energy returns before pain changes at all.
Many describe it as turning down the volume rather than switching something off. A day that used to end at 3 p.m. now reaches evening. That is a meaningful change even when the pain has not disappeared.
Being clear about this up front matters. If you expect to be pain-free in a month, you will judge LDN a failure even if it is helping.
Cost and Access
LDN must be compounded, since the low doses are not sold commercially. Most patients pay a modest monthly cost out of pocket, and insurance rarely covers it because the use is off-label.
Compared with most medications used for chronic pain and autoimmune disease, it remains one of the least expensive options available.
We prescribe LDN by telehealth across Washington and Idaho from our clinic in Spokane. Book a free 15-minute call to talk about whether a trial makes sense for your condition.