Yoon Hang Kim, MD

Board Certified in Preventive Medicine

Integrative and Functional Medicine Physician

Clinical Practice: www.directintegrativecare.com

1:1 MD & Independent Practice NP Mentoring | Health Systems Consulting: www.yoonhangkim.com

February 2026

The Medication You’ve Never Heard Of

If you’re living with a chronic condition—fibromyalgia, an autoimmune disease, chronic pain, Long COVID, or something your doctors can’t quite put a name to—there’s a medication that’s been quietly helping patients for decades. It costs less than a dollar a day. It has very few side effects. And there’s a good chance no one has ever mentioned it to you.

It’s called low-dose naltrexone, or LDN for short.

I’ve been prescribing LDN for over twenty years. I’ve used it in cancer centers, university medical centers, pain clinics, and my own integrative medicine practice. I’ve seen it change lives. I’ve also seen it not work. And I think you deserve to know the full, honest story—not a sales pitch, but the real picture of what this medication can and can’t do.

So What Exactly Is LDN?

Naltrexone is a medication that was originally developed in 1963 and approved by the FDA in 1984 to help people recovering from opioid and alcohol addiction. At that dose—around 50 to 150 milligrams—it works by blocking the brain’s opioid receptors so that drugs and alcohol don’t produce the same “high.”

But here’s where it gets interesting. When you take naltrexone at a much lower dose—typically between 0.5 and 4.5 milligrams—it does something completely different. Instead of shutting down your body’s natural pain and immune systems, it gently nudges them into working better.

Think of it this way: a high dose is like putting a brick on the gas pedal of your opioid system. A low dose is more like tapping the brakes for just a moment—just long enough for your body to say, “Hey, I need to make more of my own natural painkillers and immune regulators.” And then it does exactly that.

Three Ways LDN Helps Your Body

After two decades of prescribing LDN and studying the research, I’ve come to see it as working in three main ways. Understanding these can help you have a more informed conversation with your doctor.

1. It Boosts Your Body’s Natural Painkillers

Your body makes its own painkillers called endorphins. You know that “runner’s high” people talk about? That’s endorphins at work. They don’t just manage pain—they also help regulate your immune system, keeping it from attacking your own tissues (which is what happens in autoimmune diseases).

When you take LDN at bedtime, it briefly blocks your endorphin receptors. Your brain notices and responds by producing more endorphins. By morning, those extra endorphins are flowing through your system, helping to calm inflammation, reduce pain, and bring your immune system back into balance.

Research going back to the 1980s has shown that this endorphin boost can increase the activity of natural killer cells—your immune system’s front-line defenders against infection and even cancer. Studies in animals with autoimmune conditions found that they had lower endorphin levels before they got sick, suggesting that running low on endorphins might actually set the stage for autoimmune disease.

2. It Calms Inflammation in Your Brain and Nervous System

Your brain has its own immune cells called microglia. When these cells get activated—by an infection, injury, or chronic stress—they can get stuck in an “on” position, pumping out inflammatory chemicals that amplify pain, cause brain fog, disrupt sleep, and drain your energy. This is called neuroinflammation, and it’s increasingly recognized as a driver behind conditions like fibromyalgia, chronic fatigue, and Long COVID.

LDN helps turn these overactive immune cells back down. It does this through a specific mechanism—blocking something called Toll-like receptor 4 (TLR4)—that’s separate from its endorphin effects. In plain language: LDN helps your brain stop screaming about a fire that’s already been put out.

This is why patients often report not just less pain, but clearer thinking, better sleep, and more energy. It’s not just masking symptoms—it’s addressing one of the root causes of why you feel so terrible.

3. It Helps Your Body Find Its Balance Again

There’s a concept in natural medicine called an “adaptogen”—something that helps your body adapt to stress and return to balance. Think of a thermostat that adjusts whether you need heating or cooling. LDN appears to work this way.

I’ve had patients start LDN for insomnia and tinnitus, see significant improvement, and then—here’s the remarkable part—stay better even after stopping the medication. That’s not what happens with most drugs. Most medications only work while you’re taking them. When a medication helps your body reset and the improvement sticks, that’s a sign it’s working with your body’s own healing systems, not just overriding them.

What Conditions Can LDN Help?

In my clinical experience and based on the published research, LDN has shown promise for a wide range of conditions: autoimmune diseases (including Hashimoto’s thyroiditis, Graves’ disease, rheumatoid arthritis, multiple sclerosis, and Crohn’s disease), fibromyalgia and chronic pain syndromes, mast cell activation syndrome (MCAS), Long COVID, chronic fatigue syndrome, migraines, endometriosis, sleep disorders, and even some neurological conditions.

I’ve also used it in integrative oncology settings, where research dating back to the 1980s suggests that LDN’s immune-boosting effects—particularly its ability to increase natural killer cell activity—may support the body’s own cancer-fighting defenses.

The Honest Truth: It Doesn’t Work for Everyone

This is the part most articles leave out, and it’s the part I think matters most.

In my experience, patients fall into three groups when it comes to LDN:

Group 1: LDN is all you need. For some patients, LDN alone produces remarkable, lasting improvement. These tend to be people whose conditions are primarily driven by immune imbalance or neuroinflammation, and who haven’t been severely ill for a very long time. Published studies show response rates between 57–65% across chronic pain populations.

Group 2: LDN helps, but you need more. In more complex conditions—cancer, mold toxicity, MCAS, Long COVID, chronic Lyme—LDN plays an important role but can’t do the job alone. It calms the immune system enough to make other treatments more effective and better tolerated. Think of it as one essential member of a team, not a solo act.

Group 3: LDN doesn’t work for you. About one-third of patients don’t respond to standard LDN protocols. This doesn’t mean you’re out of options—it may mean you need a different dose, a different approach, or a different combination of therapies. But I believe you deserve to know this upfront, not after months of hoping and waiting.

Dosing: One Size Does Not Fit All

If there’s one thing I’ve learned in twenty years of prescribing LDN, it’s this: the standard “start at 1.5 mg, go to 4.5 mg” protocol works for many people, but not for everyone. And when it doesn’t, the answer isn’t always to give up—it’s often to get creative with dosing.

I think about it in terms of what I call your “endorphin reserve.” If you’ve been chronically ill for years, sleeping poorly, running on empty, and barely functioning day to day, your body’s natural endorphin stores may be severely depleted. Giving a standard dose of LDN to someone in this state is like asking a marathon runner with no training to sprint the last mile—the system just can’t respond.

For these patients, I often start at microgram levels—doses so small they’re measured in millionths of a gram—and increase very slowly over weeks or even months. Some patients need doses as low as 1 microgram to start. Others may actually need higher doses than the standard 4.5 mg—sometimes up to 25 or even 45 mg—especially for certain types of nerve pain.

The point is: if LDN didn’t work for you at one dose, that doesn’t necessarily mean LDN doesn’t work for you. It may mean you haven’t found your dose yet. This is where working with a physician who has deep experience with LDN makes a real difference.

What About Side Effects?

One of the reasons I’m comfortable prescribing LDN to such a wide range of patients is its safety profile. The most common side effects are vivid dreams and occasional temporary sleep disruption in the first few weeks. For most people, that’s it.

Compare that to the side effect lists for many commonly prescribed medications for chronic pain and autoimmune disease—immunosuppressants, steroids, opioids—and the difference is striking. LDN works with your body’s own systems rather than overriding them, which is part of why it’s so well tolerated.

One important note: LDN requires a compounding pharmacy because the commercial formulations are dosed much higher (for addiction treatment). Your doctor will need to write a prescription specifically for the low dose, and a compounding pharmacy will prepare it for you. The cost is typically between $30–60 per month.

Why Haven’t You Heard About This?

This is the question I get most often, and the answer is frustratingly simple: there’s no money in it.

Naltrexone has been a generic drug since the 1980s. No pharmaceutical company has the financial incentive to fund the large clinical trials that would lead to FDA approval for conditions like fibromyalgia or autoimmune disease. No sales representative is visiting doctors’ offices with glossy brochures about LDN. There’s no billion-dollar marketing campaign.

That doesn’t mean LDN doesn’t work. It means the system that brings medications to your doctor’s attention doesn’t have a pathway for a cheap, generic medication being used in a new way. The evidence is growing—study by study, conference by conference, patient by patient—but it’s growing through clinicians and researchers who believe in the science, not through corporate marketing budgets.

What Should You Do Next?

If you think LDN might be right for you, here’s what I’d suggest:

Talk to your doctor. Bring this article. Not all physicians are familiar with LDN, but many are increasingly open to learning about it. A physician who listens and is willing to explore options is worth their weight in gold.

Seek out an experienced prescriber. LDN is not complicated, but optimizing it—especially for complex conditions—benefits from clinical experience. A doctor who has prescribed LDN to hundreds of patients will approach dosing and troubleshooting differently than one who’s writing their first prescription.

Be patient. LDN is not a quick fix. Most patients need several weeks to a few months to see the full benefit. And if the first dose doesn’t work, there are other strategies to try before concluding it’s not for you.

Keep your expectations honest. LDN may significantly improve your quality of life. It may be one piece of a larger treatment puzzle. Or it may not be the right tool for your particular situation. All three outcomes are valid, and knowing this upfront is part of what I call “honest medicine.”

A Final Thought

For those of us living with complex, overlapping chronic conditions—especially ones that don’t fit neatly into diagnostic boxes—LDN represents something powerful. Not a miracle cure, but something perhaps even more valuable: a medication that works with your body rather than against it, at a cost nearly anyone can afford, with a safety profile that lets you try it without fear.

It won’t fix everything. But for many patients, it helps the body remember how to heal itself. And some days, that’s everything.

About the Author

Yoon Hang Kim, MD is board certified in preventive medicine and specializes in integrative and functional medicine. A graduate of Dr. Andrew Weil’s Integrative Medicine Fellowship at the University of Arizona, Dr. Kim has been prescribing LDN for over two decades across settings including Miami Cancer Institute, University of Kansas Medical Center, and community-based practices. He is the author of two books on LDN therapy and presents internationally at LDN Research Trust conferences. Dr. Kim is passionate about “honest medicine”—discussing both what treatments can do and what they can’t—and believes every patient deserves a physician who will be straight with them.

Clinical Practice: www.directintegrativecare.com

Direct Integrative Care is a membership-based telemedicine practice serving patients in Iowa, Illinois, Missouri, Georgia, Florida, and Texas.

1:1 MD & Independent Practice NP Mentoring | Health Systems Consulting: www.yoonhangkim.com

Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider before starting or modifying any treatment. LDN is not FDA-approved for the conditions discussed in this article.

© 2026 Yoon Hang Kim, MD | All rights reserved.