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LDN Q&A: Neuropathic Pain, MCAS, Insomnia, Microdosing, and What to Do When LDN Causes Side Effects

By Yoon Hang Kim, MD, MPH Board-Certified in Preventive Medicine | Integrative & Functional Medicine Physician





Low dose naltrexone (LDN) is often discussed as though there is one standard dose, one predictable response, and one straightforward way to use it.


In clinical practice, it is rarely that simple.


People differ dramatically in sensitivity, diagnosis, immune function, nervous system reactivity, medication tolerance, and response to dose changes. This becomes especially important in patients with mast cell activation syndrome (MCAS), multiple chemical sensitivity, chronic pain, neuropathy, autoimmune disease, and complex chronic illness.


During a recent LDN Support Group live session, I answered questions about some of the most common challenges people encounter with LDN. What follows are the key teaching points from that conversation.




LDN and Neuropathic Pain

One question involved using LDN for an "overactive nerve" that flares easily.


Without knowing the underlying diagnosis, it is difficult to say exactly what is being treated. However, when we are talking about neuropathic pain, LDN may be working through mechanisms beyond simply blocking opioid receptors and increasing endogenous endorphins.


One proposed mechanism involves Toll-like receptor 4 (TLR4), which is associated with glial-cell activation and neuroinflammation. When TLR4 is activated on microglia — the most prevalent immune cells of the nervous system — it can trigger a cascade of proinflammatory cytokines including interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). LDN appears to act as a TLR4 antagonist, competitively binding to the receptor and blocking downstream inflammatory signaling (Parkitny & Younger, 2017; Toljan & Vrooman, 2018).


This mechanism is particularly interesting when we think about neuropathic pain.


I experienced this personally after surgery. I developed significant nerve pain and was prescribed opioids and gabapentin. The gabapentin affected me so strongly that I could barely walk safely and needed two canes. I ultimately used naltrexone along with non-opioid pain strategies, and it made a major difference for me.


One important point is that dosing for neuropathic pain may not necessarily be identical to dosing used for autoimmune or other conditions.


The diagnosis matters.





What If LDN Causes Headache or Nausea?

Another person described starting at 0.25 mg, increasing to 0.5 mg after two weeks, and eventually reaching 0.75 mg. They subsequently developed persistent headaches and nausea.


When symptoms appear after increasing LDN, I generally do not recommend simply pushing through them.


My usual clinical approach is to back off. That may mean stopping the medication temporarily, allowing symptoms to settle, and — if LDN is restarted — returning at a much lower dose and titrating much more slowly.


I sometimes describe this pattern as being consistent with an inadequate endorphin response or "endorphin deficiency" relative to the degree of opioid receptor blockade. Whatever terminology we use, the practical message is the same: if the dose is making you significantly worse, more is not necessarily better.





LDN, Vivid Dreams, and Insomnia

Sleep disruption is one of the more commonly reported challenges with LDN. People may experience vivid dreams, difficulty falling asleep, or severe insomnia.


When someone tells me they are taking a "low dose," however, I usually ask: What dose?


The phrase "low dose" is not precise enough. For one person, 4.5 mg may be considered low dose. For another person, 0.25 mg may be far too much. A highly sensitive patient may need to begin in the microgram range.


Rather than saying, "I'm taking a low dose," tell your clinician: "I'm taking 0.5 mg." That makes the conversation much more useful.


When insomnia becomes severe after starting or increasing LDN, I consider the possibility that the dose is simply too high for that individual. Stopping and restarting much lower may be more productive than continuing to increase.





Can Symptoms Get Worse After Increasing LDN?

Yes.


A person may improve at one dose and then worsen after increasing it. That may look paradoxical, but biological systems do not always follow a simple linear dose-response curve. More medication does not automatically mean more benefit.


This is why I believe patients should participate actively in determining their LDN dosing strategy. You are the person experiencing the medication every day. Pay attention. Keep notes. Watch what happens to your sleep, pain, energy, gastrointestinal symptoms, mood, cognition, and other symptoms as the dose changes.


Individual observation can be extremely valuable.




Blood in the Stool Is Not an LDN Question

One participant described a 19-year-old with MCAS who was taking LDN. Energy had improved, but severe insomnia persisted. The person also had chronic diarrhea and blood in the stool.


At that point, the most important issue is not adjusting LDN.


Blood in the stool requires appropriate medical evaluation. Inflammatory bowel disease is one possibility, and LDN has historically been studied in inflammatory bowel disease, including pediatric populations (Smith et al., 2013). But LDN should not become a substitute for establishing the diagnosis.


If there is persistent diarrhea, bleeding, or another concerning symptom, seek appropriate medical evaluation. Treating presumed disease without first evaluating serious possibilities can be dangerous.




Can LDN Help Autoimmune Disease?

Another question came from someone with multiple autoimmune or inflammatory conditions, including Hashimoto's thyroiditis, lichen-related disease, and psoriasis.


I have seen patients with autoimmune disorders benefit from LDN. A 2019 Norwegian registry study found that persistent LDN users with rheumatoid arthritis showed a 13% relative reduction in dispensing of all rheumatic medications and a 23% reduction in analgesic use (Raknes & Småbrekke, 2019).


But I would strongly caution against thinking, "LDN must fix this."


Responses are highly individual. LDN may help modulate inflammation or symptoms, but it should not automatically be viewed as a cure or as an emergency medication designed to extinguish every inflammatory process. Sometimes conventional medicine is exactly what is needed to "put out the fire." LDN may then serve as one component of a larger strategy.




MCAS Patients May Need Extremely Small Doses

One person with MCAS told their physician they were highly medication-sensitive and wanted to start with a microdose. They were started at 1 mg.


For some patients with MCAS, 1 mg can be an enormous starting dose. In my own practice, particularly sensitive MCAS patients may begin around the microgram range. One milligram equals 1,000 micrograms. That difference matters.


Highly sensitive patients should not necessarily be treated using the same titration schedule as the average patient. MCAS changes the equation.





MCAS Diagnosis Requires Flexible Thinking

MCAS can also be challenging because laboratory testing is imperfect. There are diagnostic criteria and laboratory protocols, but no single test perfectly identifies every patient with mast cell activation.


Timing also matters. Histamine and related mediators may be transient, and some testing is most informative when performed during active symptoms. Twenty-four-hour metabolite testing may sometimes help, but even that is not perfect.


Because we do not have a single test with perfect sensitivity, clinical reasoning remains important. We should consider symptoms, history, response patterns, laboratory information, and alternative diagnoses together. Rigid thinking can cause clinicians to miss patients whose presentation does not fit neatly into one laboratory box.





LDN Is Usually Not Emergency Treatment for MCAS

One of the biggest misconceptions I see is the expectation that long-term immune-modulating therapy should behave like emergency treatment.


People frequently come to me when they are desperate. Understandably, they want something that works immediately. Sometimes a patient does experience rapid improvement.


But for many patients with MCAS, treatment requires weeks or months. The strategy may involve introducing one intervention, evaluating tolerance, titrating carefully, and then deciding whether another intervention should be added. That process cannot always be rushed.


Even medications such as omalizumab (Xolair) may require months before clinicians can properly judge the response. Immune modulation takes time.





When You Have Multiple Diagnoses, Fight One Dragon at a Time

Another participant had a combination of chronic pain, autoimmune disease, fibromyalgia, occipital neuralgia, Hashimoto's disease, anxiety, and possibly polymyalgia rheumatica.


These are not simple cases.


When someone has many overlapping diagnoses, I often use the analogy of being surrounded by dragons. LDN is one weapon. Trying to fight every dragon simultaneously with the same weapon usually creates confusion.


Instead, decide which dragon matters most. What is the primary problem? What condition is driving the greatest disability? What needs urgent conventional treatment? What problem can reasonably be addressed next?


In complex patients, I often prefer to address one major target at a time rather than changing five medications and ten supplements simultaneously. Otherwise, when something improves — or worsens — you may have no idea why.




If You Are Feeling Better, What Should You Stop First?

Someone asked what to reduce when they are doing well but taking LDN, ketotifen, exogenous ketones, and a large number of supplements.


This is another situation where individualized medical guidance helps.


In my practice, I generally do not start by removing necessary prescription medication. I am more likely to first examine the supplement list. Does every supplement still have a purpose? Was it originally prescribed for a problem that has now resolved? Are multiple products duplicating ingredients? Can the regimen be simplified?


Exogenous ketones are another area worth examining. Your body can make ketones through nutritional ketosis. Exogenous ketones may have specific uses, but they are not automatically necessary simply because someone benefits from ketosis.


Simplification should be thoughtful, deliberate, and preferably performed one change at a time.




Sublingual and Topical LDN

Questions also come up about sublingual and topical LDN.


Based on discussions I have had with compounding pharmacists, these routes may sometimes produce inconsistent results. One potential issue is the carrier and how effectively the medication reaches systemic circulation. Transdermal delivery in particular depends heavily on formulation.


Although I may think experimentally about different carriers, I am not a compounding pharmacist, and formulation decisions should ultimately be made with someone who understands pharmaceutical compounding.


Route of administration matters just as much as the number printed on the bottle.




"It Was Working Until I Increased the Dose"

Another participant had done very well at 3.5 mg but developed worsening pain after increasing to 4 mg. They then reduced to 3 mg after a 24-hour break.


This is a common lesson with LDN: if 3.5 mg works, you do not necessarily need 4 mg. There is no prize for reaching the highest dose. The goal is to identify the dose that produces the best overall response.


For some people, a 24-hour break may also be too short after developing a significant adverse reaction. In particularly sensitive patients, allowing more time for the system to settle may be reasonable before deciding what to do next.




What Does "Microdose" Actually Mean?

Terminology around LDN has become confusing. People sometimes describe 1 or 2 mg as a "microdose." Technically, however, a microgram dose is very different from a milligram dose.


For example: 1 mg = 1,000 micrograms. 2 mg = 2,000 micrograms.


When discussing LDN, I encourage people to stop relying on vague terms such as "low dose," "very low dose," "ultra-low dose," or "microdose." Instead, simply state the actual dose. The number provides much more useful clinical information.


The published literature distinguishes these ranges more precisely. Toljan and Vrooman (2018) define LDN as 1–5 mg/day, very low-dose naltrexone (VLDN) as 1 µg–1 mg, and ultra-low-dose naltrexone (ULDN) as less than 1 µg/day. These distinctions carry different pharmacodynamic implications.




Chronic Fatigue Requires a Differential Diagnosis

We also discussed testing for chronic fatigue. There is considerable interest in newer biomarkers and specialized tests. Those tests can be useful.


But chronic fatigue should still trigger a broader medical evaluation. The differential diagnosis may include sleep disorders, endocrine abnormalities, nutritional deficiencies, infections, autoimmune disease, hormonal problems, and other medical conditions.


Performing one specialized test while ignoring the major differential diagnoses is not comprehensive medicine. A better approach is to systematically evaluate the common and important possibilities while integrating newer testing when appropriate.





Rotate Sleep Tools Rather Than Depending on One Thing Forever

A final question involved supplements for sleep and mood.


One general strategy I use is to avoid relying on the same sleep intervention every night whenever possible. If one intervention works, perhaps use it selectively. Find another strategy that also works. And another. The goal is to develop a toolbox.


For example, someone might rotate among several appropriate strategies rather than repeatedly depending on one intervention until its effectiveness diminishes. Sleep is complex, and sometimes having several tools is more sustainable than looking for one perfect solution.




The Bigger Lesson: LDN Is Highly Individualized

LDN can be remarkably useful. I have seen it help with neuropathic pain, autoimmune conditions, inflammatory disorders, and complex chronic illness.


I have also seen people develop insomnia, nausea, headaches, worsening symptoms, or paradoxical reactions when the dose is wrong for them.


The lesson is not that LDN is good or bad. The lesson is that LDN is individualized.


The right question is often not, "What is the correct LDN dose?" It is: "What is the correct LDN dose for this particular person, for this particular condition, at this particular point in time?"


Start thoughtfully. Pay attention to your response. Do not assume that increasing the dose will increase the benefit. And when dealing with MCAS or highly medication-sensitive patients, remember that sometimes the difference between success and failure is simply starting much, much lower.




References

  1. Parkitny L, Younger J. Reduced pro-inflammatory cytokines after eight weeks of low-dose naltrexone for fibromyalgia. Biomedicines. 2017;5(2):16. doi:10.3390/biomedicines5020016


  1. Toljan K, Vrooman B. Low-dose naltrexone (LDN) — review of therapeutic utilization. Medical Sciences. 2018;6(4):82. doi:10.3390/medsci6040082


  1. Raknes G, Småbrekke L. Low dose naltrexone: effects on medication in rheumatoid and seropositive arthritis. A nationwide register-based controlled quasi-experimental before-after study. PLoS One. 2019;14(2):e0212460. doi:10.1371/journal.pone.0212460


  1. Smith JP, Stock H, Bingaman S, Mauger D, Rogosnitzky M, Zagon IS. Low-dose naltrexone therapy improves active Crohn's disease. Am J Gastroenterol. 2007;102(4):820-828. doi:10.1111/j.1572-0241.2007.01045.x


  1. Smith JP, Bingaman SI, Ruber F, 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. doi:10.1007/s10620-011-1653-7


  1. Pogue J, Johnson D, Burch A. A utilization review of patients that respond to low-dose naltrexone (LDN) for chronic pain. J Pain Res. 2023;16:1993-1998. doi:10.2147/JPR.S389957


  1. McKenzie-Brown AM, Boorman DW, Ibanez KR, et al. Real world effectiveness and tolerability of low dose naltrexone to treat chronic pain. J Pain Res. 2024;17:1273-1284. doi:10.2147/JPR.S451183


  1. Younger J, Noor N, McCue R, Mackey S. Low-dose naltrexone for the treatment of fibromyalgia: findings of a small, randomized, double-blind, placebo-controlled, counterbalanced, crossover trial assessing daily pain levels. Arthritis Rheum. 2013;65(2):529-538. doi:10.1002/art.37734




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Medical Disclaimer: This article is for educational and informational purposes only and does not constitute medical advice. It is not intended to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare professional before starting any new treatment, supplement, or medication. Individual responses to therapies vary, and the information presented here should not replace the clinical judgment of your physician.





Yoon Hang Kim, MD, MPH LDN Support Group | www.ldnsupportgroup.org IFMSynergy | www.ifmsynergy.com


 
 
 

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