Low Dose Naltrexone 4mg capsules provide a maintenance-strength option for patients who have completed LDN titration. So this dose usually follows a gradual build-up from 0.5mg or 1mg over 8 to 10 weeks. In particular, 4mg sits close to the widely-used 4.5mg endpoint described in most LDN clinical papers.
Furthermore, some patients settle at 4mg because it gives symptom control with fewer sleep-related side effects than 4.5mg. As a result, this strength suits established LDN users on a stable regimen.
LDN is naltrexone used at roughly one-tenth of the licensed 50mg dose. So the mechanism differs from the licensed opioid-blocking use. In particular, low doses briefly block opioid receptors overnight. Furthermore, this triggers a rebound in endogenous endorphin and enkephalin production. As a result, LDN modulates immune function and reduces neuroinflammation in ways still being characterised in research.
Each capsule contains 4mg naltrexone hydrochloride in an immediate-release format. So absorption is rapid after oral dosing. Furthermore, the compounded capsule contains no dyes and uses standard pharmaceutical excipients. As a result, the capsule suits most patients with common excipient sensitivities.
Key features
Active ingredient: naltrexone hydrochloride 4mg per capsule.
Low Dose Naltrexone 4mg for people the system has often missed
Low Dose Naltrexone 4mg capsules sit at the working end of an approach that has changed lives for patients with fibromyalgia, ME/CFS, Long COVID, Hashimoto’s, Crohn’s, ulcerative colitis, multiple sclerosis and other conditions where standard care has fallen short. So this compounded specials medicine is not a cure. However, for the right patient, at the right dose, LDN can quietly rebuild function in a way that other treatments have not. At Courier Pharmacy, we supply LDN through a proper consultation because these are complex conditions that deserve unhurried, joined-up care.
When to speak to a doctor before starting or continuing LDN 4mg
LDN is used off-label for conditions that need proper diagnosis and ongoing review. So some symptoms need urgent medical attention rather than self-managing with LDN alone:
New or worsening abdominal pain, yellowing of the skin or eyes, or dark urine, possible liver concern.
New low mood, hopelessness, or thoughts of self-harm.
Severe or persistent insomnia that hasn’t settled after dose adjustment.
Signs of opioid withdrawal (sweating, restlessness, cramps, gooseflesh) if you’ve taken any opioid painkillers in the past 7 to 10 days.
Severe headache, rash, breathing difficulty, or facial swelling after a dose.
Any planned surgery, dental procedure, or emergency needing opioid pain relief.
For life-threatening symptoms, call 999. For urgent but non-emergency concerns, call NHS 111. For LDN-specific questions, contact your prescriber at Courier Pharmacy.
Five key takeaways about LDN 4mg capsules
Low Dose Naltrexone 4mg is a compounded specials medicine. So it is unlicensed in the UK and prescribed off-label.
4mg is a common maintenance dose reached after gradual titration from 0.5mg or 1mg over 8 to 10 weeks.
LDN is used for fibromyalgia, ME/CFS, Long COVID, autoimmune conditions (Hashimoto’s, lupus, MS, Crohn’s, ulcerative colitis), CRPS, endometriosis, and post-viral fatigue syndromes.
Any opioid painkiller (codeine, tramadol, morphine, buprenorphine, methadone) is an absolute contraindication.
Every LDN supply at Courier Pharmacy follows a proper clinical assessment by our Superintendent Pharmacist Shazlee Ahsan (MSc Endocrinology, PGDip Infectious Diseases).
What is Low Dose Naltrexone (LDN): overview
The compounded specials pathway
Because LDN is unlicensed at low doses, no drug company markets it. So supply relies on UK specials manufacturers who prepare each batch to a prescription. Furthermore, this pathway is properly regulated by the MHRA under specials guidance. As a result, LDN prescribed through a UK pharmacy meets the same quality standards as any prescription medicine.
Why off-label matters here
Off-label prescribing is a normal part of UK medical practice. So the GMC and GPhC both provide guidance on it. However, off-label use places extra responsibility on the prescriber to justify the choice, and on the patient to give informed consent. In particular, our LDN consultation covers this explicitly.
A brief history
Dr Bernard Bihari, a New York neurologist, first used low doses of naltrexone in HIV patients in the mid-1980s. So the clinical use is now roughly four decades old. Furthermore, systematic research has grown steadily, particularly for fibromyalgia, Crohn’s disease, multiple sclerosis and complex regional pain syndrome. As a result, LDN now has a growing (though still limited) evidence base across several conditions.
Why choose Courier Pharmacy for your LDN 4mg
Registered, independent, and patient-led
Courier Pharmacy is a UK-registered independent pharmacy regulated by the General Pharmaceutical Council (GPhC 9010051). So when you order LDN through us, you’re working with a proper pharmacy team, not a warehouse. Furthermore, our independence means we have room to spend time on complex prescribing where a chain pharmacy would not.
Specialist prescriber expertise
Our Superintendent Pharmacist and Independent Prescriber, Shazlee Ahsan, holds an MSc in Endocrinology and a PGDip in Infectious Diseases. In particular, this matters for LDN patients because many of the conditions LDN is used for sit at the crossover of these fields. So autoimmune thyroid disease, Long COVID, chronic Lyme disease, and post-viral fatigue syndromes benefit from a prescriber who has trained in both endocrine and infectious-disease medicine. Furthermore, we understand where LDN fits alongside standard care.
Dr Ada Jex-Cori, our brand pharmacist
Our brand pharmacist is Dr Ada Jex-Cori. She represents the spirit of what we do. Named for Ada Lovelace, Sophia Jex-Blake, and Gerty Cori, she stands for evidence-led, unafraid-of-questions medicine. Her message runs through everything we prescribe:
You’re not broken. The system is. We’re here to change that.
For LDN patients in particular, this matters. So many people arrive at LDN after years of being dismissed or under-served by conventional care. Furthermore, we take those experiences as the starting point, not an inconvenience.
Structured titration support
New LDN patients need a proper titration schedule. So we supply lower strengths first (1mg, 1.5mg, 2mg, 3mg) and only move to 4mg when your response supports it. In particular, we do not simply dispense 4mg to a naive patient. Furthermore, we support the full journey from initial dose through maintenance.
Ongoing care and follow-up
LDN treatment needs monitoring. So we schedule reviews to check response, side effects, and any need to adjust the dose. Furthermore, we coordinate with your GP or specialist where relevant. As a result, LDN prescribing through Courier Pharmacy is care that keeps showing up, not a one-off transaction.
Buy Low Dose Naltrexone 4mg (Prescription Only) from Courier Pharmacy
LDN 4mg is a prescription-only medicine supplied through our LDN consultation service at courierpharmacy.co.uk. So supply follows a proper clinical assessment. In particular, new patients complete our LDN consultation before any capsules are dispensed. However, established patients moving from another provider can complete a shorter reassessment.
The four steps
Complete a quick online LDN consultation covering your diagnosis, previous treatments, current medicines, and any opioid use.
A UK prescriber reviews your answers.
If LDN 4mg is clinically appropriate, a prescription is issued.
We dispense and deliver discreetly to your door, with clear titration and follow-up guidance.
If LDN 4mg isn’t right for you
If our assessment shows a different approach fits your situation better, we’ll explain why and suggest the next best option. So this might mean starting at a lower LDN dose and titrating up, using a different formulation (LDN liquid, split doses), addressing a different underlying issue first, or a referral to a specialist. Above all, we won’t dispense a medicine that isn’t right for your situation. In short, honest guidance matters more than making the sale.
Summary
LDN is naltrexone hydrochloride at doses between 0.5mg and 4.5mg daily, roughly one-tenth of the licensed 50mg dose used for opioid and alcohol dependence.
LDN is unlicensed in the UK at these low doses. So it is supplied as a compounded specials medicine.
LDN is used off-label for autoimmune, inflammatory, chronic pain and post-viral fatigue conditions.
LDN was developed clinically by Dr Bernard Bihari from the 1980s onward, initially in HIV patients.
LDN is not a substitute for specialist care in serious autoimmune or neurological disease. So it usually adds to existing treatment.
Active ingredient
Each capsule contains 4mg of naltrexone hydrochloride. So this is the sole active ingredient. In particular, naltrexone is a pure opioid receptor antagonist. Furthermore, at low doses it produces a brief receptor blockade that triggers a rebound in endogenous opioid activity.
Excipients (inactive ingredients)
LDN 4mg capsules are compounded medicine. It contains:
Naltrexone hydrochloride
Microcrystalline cellulose
Hydroxy Propyl Methyl Cellulose (HPMG) capsules
All our LDN capsules are suitable for vegetarians.
If you have a specific excipient allergy or intolerance, tell our team before ordering. So we can arrange a suitable alternative formulation.
What is LDN 4mg used for?
LDN is prescribed off-label for a range of chronic conditions. So the evidence base is growing but remains limited for most indications. In particular, LDN is used in the following areas.
Autoimmune conditions
Hashimoto's thyroiditis and other autoimmune thyroid disease.
Chronic Lyme disease and post-treatment Lyme disease syndrome.
Postural orthostatic tachycardia syndrome (POTS).
Gynaecological conditions
Chronic pelvic pain.
Please note that LDN is not a first-line treatment for any of these conditions on the NHS. So most patients try LDN after standard treatments have not given adequate control. Furthermore, LDN often works alongside other treatments rather than replacing them.
How does Low Dose Naltrexone 4mg work?
LDN works through several distinct mechanisms that are different from the licensed 50mg dose. So the pharmacology at low doses is genuinely different, not just weaker. In particular, three main pathways are recognised, with a fourth still being characterised.
Brief opioid receptor blockade and endorphin rebound
At bedtime dosing, LDN briefly occupies mu-opioid receptors for around 4 to 6 hours. So this is much shorter than the 24-hour block seen at 50mg. Furthermore, the body responds to this brief blockade by increasing its own production of endorphins, enkephalins and other endogenous opioids. As a result, the rebound in endogenous opioid tone continues well after the naltrexone itself has cleared.
In particular, this rebound in met-enkephalin (also called opioid growth factor) appears central to LDN's effects on cell proliferation and immune regulation. So the increased endogenous opioid activity acts on tissues throughout the body over the following hours. Furthermore, patients often notice improved mood, reduced pain, and better sleep quality within the first month, which fits this proposed mechanism.
TLR4 antagonism and reduced neuroinflammation
Naltrexone binds to Toll-like receptor 4 (TLR4) on microglia, the immune cells of the central nervous system. So this binding reduces microglial activation. Furthermore, reduced microglial activation lowers the production of pro-inflammatory cytokines such as TNF-alpha, IL-1 beta, and IL-6 within the brain and spinal cord.
This TLR4 mechanism appears especially important in conditions where central sensitisation and neuroinflammation drive the symptoms. In particular, this includes fibromyalgia, ME/CFS, small fibre neuropathy and Long COVID. As a result, LDN acts as a central anti-inflammatory agent in a way that does not depend on opioid receptors at all.
Immune system modulation
LDN appears to normalise immune function rather than simply suppress it. So T-cell balance shifts toward a less inflammatory profile, with changes in Th1, Th2 and Th17 activity. Furthermore, regulatory T-cell function is often enhanced. As a result, autoimmune inflammatory drive tends to reduce over months of treatment.
This immune-normalising effect helps explain the response seen in Crohn's disease, multiple sclerosis and autoimmune thyroid disease. In particular, published trials in Crohn's disease have shown mucosal healing in patients on LDN. Furthermore, small studies in multiple sclerosis have shown improvements in quality of life and reduced fatigue.
Effects on pain processing and central sensitisation
Chronic pain conditions such as fibromyalgia, CRPS and endometriosis involve amplified pain processing in the central nervous system. So the pain signal is real, but it is being turned up rather than accurately reported. Furthermore, this amplification (central sensitisation) has proved very hard to treat with standard analgesics.
LDN reduces central sensitisation through the combined TLR4 and endogenous opioid effects above. In particular, this can lower background pain levels and reduce the frequency of pain flares. Furthermore, some patients notice a reduced startle response, improved sleep quality, and better cognitive stamina alongside the pain benefit.
Sleep architecture and REM effects
LDN affects sleep in ways that are still being characterised. So vivid dreams in the first few weeks are common and usually settle. Furthermore, many patients report deeper, more restorative sleep once past this initial phase. In particular, improved sleep quality often contributes to daytime energy improvements independently of the direct pain and immune effects.
Timing, pharmacokinetics, and why once-daily works
Naltrexone has a plasma half-life of about 4 hours. So at low doses, the drug clears within a few hours of a bedtime dose. However, its effects on receptors, glial cells and endogenous opioid production persist for much longer. As a result, once-daily dosing is sufficient for most patients despite the short half-life.
Bedtime dosing has become the traditional approach because it uses the natural overnight peak in endogenous opioid production. In particular, endorphin release is highest between 2am and 4am. So blocking receptors briefly during this window is thought to maximise the rebound. However, morning dosing works well for patients whose sleep is disturbed by bedtime dosing, and appears to give similar clinical benefit.
Treatment dosage
The usual maintenance dose is between 3 and 4.56mg once daily. So most patients take LDN at bedtime. However, some patients find morning dosing suits them better if bedtime dosing disturbs sleep. In particular, your prescriber will confirm the timing that fits your response.
Typical titration schedule
Most patients build up gradually over 8 to 10 weeks:
Week 1: 0.5mg daily
Week 2: 1mg daily
Week 3: 1.5mg daily
Week 4: 2mg daily
Week 5: 3mg daily
Week 6: 4-4.5mg daily
However, individual response varies significantly. So your prescriber may recommend a slower titration or a different endpoint. Furthermore, some patients settle at doses below 4mg and never need the full 4.5mg.
If a dose is missed
Take the missed dose as soon as you remember on the same day. However, if it is nearly time for the next dose, skip the missed dose. So never take a double dose to make up for a missed one.
How to take LDN 4mg capsules
Swallow one capsule whole with a glass of water.
Take at the same time each day for consistent effect.
Bedtime dosing depending on whether sleep is disturbed or not.
Morning dosing suits patients who experience sleep disruption from bedtime dosing.
LDN can be taken with or without food.
Do not open or crush the capsule unless your prescriber advises.
Continue treatment as advised. So response often develops over 2 to 6 months.
Warnings and precautions
Opioid use is a strict contraindication
LDN blocks opioid receptors. So patients taking opioid painkillers cannot use LDN. In particular, this includes:
Codeine and co-codamol.
Tramadol and tapentadol.
Morphine, oxycodone and hydromorphone.
Fentanyl patches or lozenges.
Buprenorphine (including transdermal patches).
Furthermore, opioids must be stopped for at least 7 to 10 days before starting LDN. So this avoids precipitated withdrawal. In particular, longer-acting opioids such as methadone or buprenorphine need a longer washout.
Planned opioid use
If you need opioid analgesia (planned surgery, dental procedure or trauma), LDN must be stopped in advance. So typically 24 to 72 hours before opioid use is enough. Furthermore, tell any anaesthetist or emergency clinician that you take LDN.
Liver function
Naltrexone is metabolised by the liver. So severe liver impairment is a caution. In particular, mild to moderate liver disease does not usually prevent LDN use. However, your prescriber may request liver function tests before or during treatment.
Pregnancy and breastfeeding
Safety data for LDN in pregnancy and breastfeeding is limited. So LDN is not usually recommended in these situations. Furthermore, tell your prescriber if you plan to become pregnant.
Autoimmune thyroid disease
LDN may improve autoimmune thyroid function. So thyroid hormone doses may need adjustment during treatment. Furthermore, patients on levothyroxine or liothyronine should have thyroid function monitored more frequently after starting LDN.
Side effects
Common early side effects
Most side effects settle within 2 to 4 weeks. So they often reflect the initial rebound in endogenous opioid activity:
Vivid dreams or nightmares.
Sleep disturbance or insomnia.
Mild headache.
Nausea or gastrointestinal upset.
Mild anxiety or restlessness.
Managing early side effects
Several strategies help patients settle:
Switch to morning dosing if bedtime dosing disturbs sleep.
Slow the titration by staying at each dose step for longer.
Split the dose (some patients find twice-daily lower doses easier).
Take with food if nausea occurs.
Less common side effects
Mood changes.
Fatigue during the day.
Skin rash.
Muscle aches.
Rare but important
Signs of liver dysfunction (jaundice, dark urine, right upper abdominal pain).
Precipitated opioid withdrawal in patients who did not fully disclose opioid use.
Yellow Card scheme: report any suspected side effects via https://yellowcard.mhra.gov.uk or the Yellow Card app. Reporting helps make medicines safer for everyone.
Drug interactions
Absolute contraindication: opioid analgesics
All opioid painkillers interact with LDN. So concurrent use blocks the analgesic effect of the opioid. Furthermore, in opioid-dependent patients, LDN precipitates withdrawal.
Levothyroxine and liothyronine
LDN may improve autoimmune thyroid function. So thyroid hormone requirements may fall. Furthermore, patients on thyroid hormone replacement need TSH monitoring during the first 3 to 6 months of LDN.
Immunosuppressants
Data on LDN combined with drugs such as methotrexate, azathioprine or biologics is limited. So your specialist will guide any combination. Furthermore, LDN is not a substitute for established disease-modifying therapy in most autoimmune conditions.
Alcohol
Occasional moderate alcohol is not usually a problem. However, heavy or frequent alcohol may affect liver function. So sensible drinking limits apply.
Frequently asked questions about LDN 4mg
Is LDN 4mg licensed in the UK?
No. LDN is unlicensed at low doses. So it is supplied as a compounded specials medicine under MHRA specials regulations. Furthermore, prescribing follows GMC and GPhC off-label guidance.
How quickly does LDN 4mg work?
Response varies. So some patients notice improvement within 2 to 4 weeks. However, most patients need 2 to 6 months for full benefit. Furthermore, some conditions respond faster than others; fibromyalgia and neuropathic pain often respond earlier than autoimmune inflammation.
Is 4mg the maximum LDN dose?
No. Standard LDN dosing typically goes up to 4.5mg. So 4mg is a common maintenance dose. However, some patients need higher off-label doses (5mg or 6mg) under specialist supervision.
Can I stop LDN 4mg suddenly?
Yes. LDN does not cause physical dependence. So there is no withdrawal on stopping. However, symptoms of the underlying condition often return within days to weeks, so tapering may not be needed but the reason for treatment usually returns.
Can I take LDN 4mg with paracetamol or ibuprofen?
Yes. Paracetamol, ibuprofen, naproxen and other non-opioid painkillers do not interact with LDN. So these remain the first-line options for pain relief while on LDN.
Does LDN 4mg interact with alcohol?
Moderate occasional alcohol is not usually a problem. However, heavy drinking may affect liver function and reduce LDN's benefits. So the standard UK 14-units-a-week guidance applies.
Do I need blood tests during LDN treatment?
Not routinely for LDN itself. However, your prescriber may recommend baseline liver function tests before starting or during treatment. Furthermore, patients on thyroid hormone replacement need TSH and free T4 monitoring after starting LDN.
Can I take LDN 4mg alongside my other autoimmune medicines?
Usually yes. So LDN is often added to existing treatment rather than replacing it. However, some combinations need specialist review, particularly with biologics or high-dose immunosuppressants. Furthermore, our LDN consultation covers this in detail.
Will LDN 4mg affect my mental health medicines?
Antidepressants, mood stabilisers and anxiolytics do not usually interact with LDN. However, LDN may cause vivid dreams or sleep changes in the first weeks that could affect existing sleep problems.
What happens if I need surgery while taking LDN 4mg?
Stop LDN 24 to 72 hours before planned surgery. So opioid analgesia will work normally during and after your procedure. Furthermore, tell your anaesthetist that you take LDN.
Can I use LDN 4mg during pregnancy?
LDN is not usually recommended in pregnancy or breastfeeding because safety data is limited. So women planning imminent pregnancy should pause LDN and discuss timing with their prescriber.
Is LDN 4mg safe long-term?
LDN has been used off-label for over 30 years with a favourable safety profile at low doses. So most patients tolerate it well over years of use. However, ongoing prescriber review remains important, particularly for liver function and thyroid function where relevant.
Can children or teenagers take LDN 4mg?
Some paediatric use of LDN exists (particularly in Crohn's disease) but always under specialist care. So we do not routinely supply LDN for under-18s. Furthermore, any paediatric LDN case would need referral to a specialist paediatric prescriber.
Why is 4mg an unusual dose (not 4.5mg)?
4mg is a common stable maintenance point that some patients settle at. In particular, some find 4.5mg causes more sleep disruption, and step back to 4mg. So the 4mg strength provides a practical option for this group. Furthermore, capsule strengths are prepared in 0.5mg increments by specials manufacturers.
Can I switch from LDN liquid to 4mg capsules?
Yes. So most patients switching from an equivalent liquid dose can move straight to 4mg capsules. However, tell your prescriber about your current dose and any adjustments so we can confirm the switch is safe.
Does LDN 4mg help with Long COVID?
Emerging evidence and clinical experience support LDN use in Long COVID, particularly for fatigue, brain fog and post-exertional malaise. So this is one of the most common reasons patients ask about LDN today. However, the evidence base is still developing, and LDN is not a licensed Long COVID treatment.
Does LDN 4mg help with fibromyalgia?
Fibromyalgia has some of the strongest evidence for LDN in chronic pain. In particular, systematic reviews of small trials show pain reduction and improved quality of life. So LDN is often tried when pregabalin, duloxetine and amitriptyline have not given adequate control.
Can I drive while taking LDN 4mg?
Yes for most patients. So LDN does not usually cause sedation at low doses. However, if you experience vivid dreams that disturb sleep or daytime fatigue in the first few weeks, be cautious about driving until you know how LDN affects you.
Is LDN 4mg suitable for people with liver problems?
Mild to moderate liver disease usually does not prevent LDN use. So your prescriber may request liver function tests before starting. However, severe liver impairment is a caution and would need specialist input.
How do I know if LDN 4mg is the right dose for me?
This is a prescriber decision based on your response to lower doses and any side effects. So most patients titrate up through 1mg, 2mg, 3mg before reaching 4mg. Furthermore, if 4mg gives good control without side effects, there is often no reason to increase further. In particular, our follow-up review covers this in detail.
Disclaimer
Disclaimer: This information is for education only and isn't a substitute for personal medical advice. Always follow your prescriber's instructions.
References
Younger, J., Parkitny, L. and McLain, D. (2014). The use of low-dose naltrexone (LDN) as a novel anti-inflammatory treatment for chronic pain. Clinical Rheumatology, 33(4), pp.451–459. Available at: https://link.springer.com/article/10.1007/s10067-014-2517-2
Toljan, K. and Vrooman, B. (2018). Low-Dose Naltrexone (LDN): Review of Therapeutic Utilization. Medical Sciences (Basel), 6(4), p.82. Available at: https://www.mdpi.com/2076-3271/6/4/82
Smith, J.P., Bingaman, S.I., Ruggiero, F., Mauger, D.T., Mukherjee, A., McGovern, C.O. and Zagon, I.S. (2011). Therapy with the opioid antagonist naltrexone promotes mucosal healing in active Crohn's disease: a randomized placebo-controlled trial. Digestive Diseases and Sciences, 56(7), pp.2088–2097. Available at: https://link.springer.com/article/10.1007/s10620-011-1653-7
Cree, B.A.C., Kornyeyeva, E. and Goodin, D.S. (2010). Pilot trial of low-dose naltrexone and quality of life in multiple sclerosis. Annals of Neurology, 68(2), pp.145–150. Available at: https://onlinelibrary.wiley.com/doi/10.1002/ana.22006
Parkitny, L. and Younger, J. (2017). Reduced Pro-Inflammatory Cytokines after Eight Weeks of Low-Dose Naltrexone for Fibromyalgia. Biomedicines, 5(2), p.16. Available at: https://www.mdpi.com/2227-9059/5/2/16
