Reading time: 12 minutes | Last updated: July 2026 | Written by the LCJ Team
Part of the LCJ series: Long Covid Supplements: What the Evidence Actually Shows | Long Covid Treatments: What Actually Works?
Experimental treatments for Long Covid are attracting increasing interest because conventional medicine still has few proven options for many patients. These treatments including peptides, methylene blue and other emerging therapiesare being investigated because they target biological pathways thought to contribute to Long Covid, including immune dysregulation, mitochondrial dysfunction, inflammation and tissue repair. However, for almost all of these treatments, the biological rationale is considerably stronger than the clinical evidence. Most have little or no high-quality human research in people with Long Covid, many are not approved for this use, and some carry important safety risks or significant uncertainties regarding dosing, product quality and long-term effects. They should be regarded as experimental rather than established treatments and, where considered, should only be explored under appropriate medical supervision.
Key Facts
- What are they? Experimental substances including peptides, methylene blue and other compounds that are being explored because of their potential effects on immune function, mitochondria, inflammation and tissue repair.
- Why are people interested? They target biological mechanisms that researchers believe may contribute to Long Covid, including persistent inflammation, immune dysfunction and impaired cellular energy production.
- What does the evidence show? Most evidence comes from laboratory studies, animal research or small early human studies. Robust clinical trials in Long Covid are still lacking for almost all of these treatments.
- Are they approved? Most are not approved for the treatment of Long Covid, and several are not approved for routine human use in many countries.
- What are the risks? Potential risks include serious medication interactions, unknown long-term safety, inconsistent product quality, contamination and the absence of established dosing protocols.
- Bottom line: These treatments are scientifically interesting and may help guide future research, but they remain experimental. At present, they should not be considered proven treatments for Long Covid.
⚠️ Read this first
This article covers substances that are not approved for human use in most countries, are not regulated as supplements or medicines, and are being self-administered by some people with Long Covid based on animal research or very limited human data. This is not a guide to how to use these substances. It is a guide to understanding what they are, what the science currently shows, and why medical oversight matters here more than anywhere else in this series. Desperation is a reasonable response to an illness that conventional medicine does not yet know how to treat well. We want to say that clearly before anything else.
When someone has been unwell for years, been discharged from multiple clinics, tried evidence-based treatments, and is still unable to work or live the life they had, looking beyond conventional medicine is not reckless it is human. The experimental approaches discussed here have gained attention because many people with Long Covid are searching for options in the absence of established treatments.
What this guide adds is the information that is often missing from online discussions: the specific risks, the specific unknowns, and the reasons why some of these substances should not be self-administered without appropriate medical oversight not as a matter of caution for its own sake, but because of genuine pharmacological risks.
This article is not intended to help you choose an experimental treatment. Its purpose is to explain why these substances are being discussed, what the current evidence actually shows, and where the important uncertainties remain.
If You Decide to Explore Experimental Treatments
Many of the substances discussed in this guide are being investigated because conventional medicine does not yet have effective treatments for Long Covid. It’s understandable that some people decide to explore experimental options, particularly after years of persistent symptoms. If you choose to do so, it is strongly advisable to seek guidance from a suitably qualified clinician who is familiar with the treatment being considered, understands the available evidence, and is willing to work with your existing healthcare team where appropriate.
Be cautious of anyone who promises a cure, recommends multiple experimental treatments without a clear rationale, discourages appropriate medical care, or dismisses the importance of monitoring and safety. The history of medicine is full of treatments that looked promising in laboratory studies or animal models but ultimately failed in human clinical trials. Some eventually became valuable medicines; many did not.
Long Covid research is moving quickly, but for most of the substances discussed in this guide, the biological rationale is currently stronger than the clinical evidence. Curiosity is reasonable. Hope is understandable. The evidence is still catching up.
The goal should always be carefully supervised decision-making, not uncontrolled self-experimentation.
This article is part of the LCJ supplements series. For mainstream supplements including vitamins, antioxidants, and mitochondrial supplements, see Long Covid Supplements: What the Evidence Actually Shows. For herbal medicines, see Herbal Medicines and Long Covid.
Jump to
- Methylene Blue
- Peptides — Overview
- BPC-157
- Thymosin Alpha-1
- KPV
- LL-37
- Shilajit
- A Note on Low Dose Naltrexone
- FAQs
The Regulatory Context Worth Understanding
The substances in this article occupy a specific regulatory gap. They are not:
- Licensed pharmaceutical drugs (approved for human use after clinical trials)
- Regulated supplements (sold legally as food supplements under consumer protection rules)
- Approved as veterinary medicines in most cases
Most are classified as research chemicals legal to purchase in some jurisdictions for laboratory use, but not approved for human administration. Their manufacture is not subject to pharmaceutical Good Manufacturing Practice standards. Quality control, purity, and dosing accuracy cannot be assumed from commercial sources.This matters practically because a vial labelled “BPC 157 5mg” purchased from a research chemical supplier may contain the correct compound at the labelled dose or it may not. There is no regulatory framework ensuring it does.
We are aware that describing regulatory status can read as a bureaucratic hedge rather than useful information. Here is why it actually matters: three of the substances in this guide have serious adverse effects at incorrect doses or in combination with other medications. The adverse effects are not theoretical they are documented in case reports. The regulatory status is how the information that prevents those adverse effects is usually communicated. It is not a reason to dismiss the substances. It is a reason to take the safety information in this article seriously.
Methylene Blue
Short answer: A pharmaceutical dye with genuine mitochondrial mechanisms generating significant interest in Long Covid communities. The biological rationale is among the most compelling in this entire article series. The safety risks in combination with certain medications are among the most serious. These two things are both true simultaneously.
What it is
Methylene blue is a synthetic dye first synthesised in 1876, which has been in clinical use for over a century primarily as an antidote for methaemoglobinaemia (a blood oxygen disorder) and as a surgical tissue stain. At pharmacological doses it is a monoamine oxidase inhibitor (MAOI) and has been studied for Alzheimer’s disease under the name hydromethylthionine.
Why Long Covid patients are interested
The biological rationale for methylene blue in Long Covid is genuinely interesting and worth understanding. Methylene blue acts as an alternative electron carrier in the mitochondrial respiratory chain it can accept electrons at Complex I and donate them further along, potentially bypassing dysfunctional steps in the mitochondrial energy production pathway. Given the confirmed mitochondrial dysfunction in Long Covid, this mechanism is directly relevant. It also has antioxidant effects, has been shown to reduce neuroinflammation in animal models, and has demonstrated neuroprotective effects in multiple neurological conditions. The combination of mitochondrial support and neuroprotection makes it particularly appealing for Long Covid brain fog and fatigue.
Proposed mechanisms in Long Covid
- Alternative electron carrier in mitochondrial respiratory chain may bypass dysfunctional steps
- Antioxidant effects including reduction of reactive oxygen species
- Reduced neuroinflammation in animal models
- Improved cerebral blood flow in some conditions
- Potential antiviral properties at specific concentrations
- Inhibition of nitric oxide synthase relevant to some proposed Long Covid vascular mechanisms
What the evidence actually shows
The evidence for methylene blue in Long Covid specifically is extremely limited case reports and anecdotal accounts, not controlled trials. The evidence base comes from its established clinical uses (methaemoglobinaemia) and preclinical research in neurological conditions. The biological rationale is compelling; the clinical evidence in Long Covid humans is not yet there.
The safety risks
⚠️ Methylene blue safety — critical information:
Serotonin syndrome risk: Methylene blue is a potent inhibitor of monoamine oxidase A (MAO A) at doses above approximately 0.5-1mg/kg. Combining it with any serotonergic medication SSRIs, SNRIs, tramadol, triptans, St John’s Wort, some antihistamines, some opioids can cause serotonin syndrome. Serotonin syndrome can cause fever, agitation, muscle rigidity, rapid heart rate, and in severe cases seizures and death. This is not a theoretical risk case reports of serotonin syndrome from methylene blue combined with serotonergic drugs are documented in the medical literature, including deaths.
G6PD deficiency: Methylene blue causes haemolysis (red blood cell destruction) in people with glucose 6 phosphate dehydrogenase (G6PD) deficiency an inherited enzyme deficiency affecting approximately 400 million people worldwide, more common in people of African, Mediterranean, and Middle Eastern descent. G6PD status should be confirmed before any methylene blue use.
Dose dependence: At very low doses (below 1mg/kg), methylene blue acts as an antioxidant. At higher doses it becomes pro oxidant the opposite effect. The dose response curve is not linear. Self dosing without clinical oversight makes dose accuracy difficult.
Blue discolouration: Methylene blue turns urine and sometimes skin blue or green. This is harmless but alarming without forewarning.
Medication interactions: Beyond serotonergic drugs, methylene blue interacts with anticoagulants, some antibiotics, and other medications. Full interaction check with a pharmacist is essential.
Who might consider it and how
For Long Covid patients not taking any serotonergic medications, without G6PD deficiency, and with access to clinical supervision methylene blue is being used and some patients report meaningful improvements in fatigue and cognitive function. The doses being used in Long Covid communities are typically low (1-4mg total dose, not per kg), below the threshold at which MAO A inhibition becomes significant. However, there is no established protocol and no controlled evidence.If you are considering methylene blue, the minimum requirements are: confirm you are not on any serotonergic medication (including St John’s Wort), confirm your G6PD status, discuss with a clinician who is familiar with the safety profile, and do not obtain it from an unverified source.
[🔵 Limited clinical evidence] in Long Covid. Compelling biological rationale. Serious safety risks require clinical oversight. Not appropriate for self administration without medical supervision.
Peptides — An Overview
Peptides are short chains of amino acids essentially small proteins that act as signalling molecules in the body. The body produces thousands of its own peptides that regulate immune function, tissue repair, hormone release, and nerve signalling. The peptides in this section are synthetic versions of naturally occurring sequences, or novel sequences designed to mimic biological effects.
Interest in peptides for Long Covid arises from their targeted mechanisms rather than the broad effects of most supplements, peptides in theory target specific biological processes. The challenge is that most research has been conducted in animal models, the human pharmacokinetics (how they behave in the human body) are poorly characterised, manufacturing quality varies significantly, and administration is typically via subcutaneous injection rather than oral supplements with the associated risks of sterile technique.
The peptide conversation in Long Covid communities is genuinely one of the more scientifically interesting areas the mechanisms are specific, the animal data is sometimes impressive, and the desperation driving people to try them is entirely understandable. It is also one of the areas where the gap between animal research and human clinical evidence is largest. We have tried to represent both of those things accurately.
BPC-157 (Body Protection Compound-157)
Short answer: Synthetic peptide derived from a protein in gastric juice. Impressive tissue repair and anti inflammatory effects in animal studies. Almost no human clinical trial data. Not approved for human use. Being self administered by some Long Covid patients subcutaneously or orally.
What it is
BPC 157 is a 15 amino acid peptide sequence derived from a protein found in human gastric juice. It does not occur naturally in isolation it is a synthetic research compound. Animal research has shown consistent effects on tissue repair, wound healing, gut repair, tendon healing, and neuroprotection. It appears to work through multiple pathways including growth hormone receptor modulation, nitric oxide production, and angiogenesis (blood vessel formation).
Why Long Covid patients are interested
The mechanisms most relevant to Long Covid are: gut repair effects (relevant to gut permeability and dysbiosis), neuroprotective effects (relevant to brain fog), anti inflammatory activity, and potential support of endothelial function. In animal models, BPC 157 has shown remarkable ability to repair gut lining damage and reduce neuroinflammation.
What the evidence actually shows
The animal evidence is genuinely impressive in breadth and consistency BPC 157 has positive results across many injury and disease models in multiple animal species. The human clinical evidence is extremely limited. One small human trial in inflammatory bowel disease showed positive signals. There are no controlled human trials in Long Covid or post viral conditions.
A significant question is whether orally administered BPC 157 survives digestion it is a peptide and should theoretically be broken down by gut enzymes before absorption. Some researchers argue that its derivation from a gastric protein means it has inherent stability in this environment. This has not been established in human pharmacokinetic studies.
Administration and safety
BPC 157 is being self administered by some Long Covid patients either subcutaneously (injected under the skin) or orally (as capsules or liquid). Subcutaneous injection of a research chemical purchased from an unregulated source carries risks of contamination and injection site infection. Oral administration has uncertain bioavailability. No serious adverse effects have been reported in animal studies at therapeutic doses, but human safety data is absent.
[🔵 Limited clinical evidence] in humans. Impressive animal data. No human Long Covid trials. Not approved for human use. Quality of commercially available products cannot be guaranteed. Requires careful risk assessment.
Thymosin Alpha-1 (Tα1)
Short answer: This one is different from the others in this section thymosin alpha-1 is an approved pharmaceutical in some countries, has meaningful human clinical trial data, and has been studied in post Covid conditions.Compared with most substances discussed in this guide, thymosin alpha-1 has a substantially larger human safety database. However, evidence for Long Covid remains limited, and access rather than safety is currently the main barrier.
What it is
Thymosin alpha-1 is a naturally occurring peptide produced by the thymus gland. It plays an important role in T cell maturation and immune regulation. A synthetic version (thymalfasin, brand name Zadaxin) is approved as a pharmaceutical in over 35 countries including China, Italy, and several other European and Asian countries primarily for hepatitis B, hepatitis C, and as an immune adjuvant in cancer treatment and severe infections.
The Long Covid evidence
Thymosin alpha-1 was used in China during the Covid 19 pandemic as part of treatment protocols for severe disease. Several Chinese studies reported positive outcomes. A small Italian study found meaningful improvements in immune parameters and clinical outcomes in Long Covid patients with persistent immune dysregulation treated with thymalfasin.
The immune modulating mechanism supporting T cell function and reducing inappropriate immune activation — maps directly onto the immune dysregulation documented in Long Covid. Of all the experimental approaches in this article, thymosin alpha-1 has the closest to an established safety profile and the most relevant human trial data for post Covid conditions.
Access and barriers
Thymalfasin is not approved in the UK or US for any indication. Access requires either travel to a country where it is approved, private prescription from a specialist willing to prescribe off label, or purchasing from online sources with uncertain quality. Cost is significant. For patients with documented immune dysregulation — confirmed on specialist immunological testing a referral to an immunologist to discuss thymalfasin access may be worth pursuing.
[🟡 Promising early research] in post Covid immune dysregulation. Approved pharmaceutical in some countries with meaningful safety data. Not approved in UK or US. Access is the primary barrier rather than evidence.
KPV
Short answer: Tripeptide fragment of alpha melanocyte stimulating hormone (alpha MSH). Anti inflammatory and gut protective effects in animal models. Very limited human data. Being used in the Long Covid community primarily for gut symptoms and neuroinflammation.
What it is
KPV is a three amino acid peptide (lysine proline valine) derived from the C terminal sequence of alpha MSH a naturally occurring hormone with well documented anti inflammatory effects. It binds to melanocortin receptors that regulate inflammation, gut function, and neuroprotection. Animal studies have shown anti inflammatory effects in gut conditions, reduced neuroinflammation, and antimicrobial properties.
Why Long Covid patients are interested
The primary interest is in its anti inflammatory effects particularly in the gut (relevant to Long Covid gut symptoms and gut barrier disruption) and the nervous system (relevant to brain fog and neuroinflammation). Its small size means it may have better oral stability than larger peptides.
The evidence and safety
Human clinical evidence is very limited primarily animal studies and in vitro research. No serious adverse effects have been documented in animal studies at doses used experimentally, but human pharmacokinetic and safety data is absent. Not approved for human use in any jurisdiction we are aware of. Quality of commercially available KPV cannot be guaranteed.
[🔵 Limited clinical evidence] Interesting anti inflammatory mechanism. Animal data encouraging but very limited. Human evidence essentially absent. Not approved for human use.
LL-37
Short answer: Naturally occurring human antimicrobial peptide with immune modulating properties. Interest in Long Covid relates to its antiviral and immune regulatory effects. Very limited human data. Administration and sourcing concerns are significant.
What it is
LL 37 is the only known human cathelicidin a type of antimicrobial peptide produced naturally by immune cells, skin cells, and epithelial cells. It has broad spectrum antimicrobial activity, antiviral properties, and immune modulating effects. It regulates inflammatory responses and supports tissue repair.
Why Long Covid patients are interested
The antiviral properties (documented against several enveloped viruses), immune modulating effects, and potential relevance to viral persistence in Long Covid drive interest. Some researchers have noted that LL 37 levels may be altered in Covid 19 and post Covid conditions.
The evidence and significant concerns
Human clinical data on exogenous LL 37 administration is essentially absent. There are important pharmacological concerns: LL 37 at higher concentrations has cytotoxic effects on human cells the therapeutic window in humans is not established. It also has complex dose dependent immune effects it can both stimulate and suppress immune responses depending on concentration and context.
Administration by injection of a poorly characterised research chemical is a significant concern here more than with some other peptides, given the cytotoxicity data at higher concentrations.
[🔵 Limited clinical evidence] Interesting biological rationale. Significant concerns about cytotoxicity at higher concentrations and absence of human pharmacokinetic data. Requires careful consideration before any use.
Shilajit
Short answer: A mineral resin from Himalayan and Central Asian mountain ranges containing fulvic acid and trace minerals. Long history in Ayurvedic medicine. Some human trial data for testosterone and mitochondrial function. Quality and contamination are significant concerns.
What it is
Shilajit is a blackish resinous substance that oozes from rock crevices in high altitude mountain ranges — the result of centuries of microbial decomposition of plant matter. It contains fulvic acid, humic acids, trace minerals, and various organic compounds. It has been used in Ayurvedic medicine for thousands of years and is classified as a rasayana — a rejuvenating substance.
The evidence
Unlike most substances in this article, shilajit has some human clinical trial data. A randomised trial found that purified shilajit supplementation raised testosterone levels in healthy men with low normal testosterone. A 2019 study found improvements in muscle strength and recovery. The fulvic acid component has mitochondrial supporting effects demonstrated in laboratory studies.
For Long Covid, the mitochondrial supporting effects via fulvic acid are the primary biological rationale. The evidence is not strong but is more developed than for most peptides.
Quality and contamination — the primary concern
Shilajit quality varies enormously between products and sources. Heavy metal contamination lead, arsenic, mercury has been documented in poorly processed commercial shilajit products. Authentic, properly purified shilajit from reputable sources has a reasonable safety profile at normal doses. Poorly processed products from unknown sources carry real contamination risk.
If you choose to try shilajit:
- Purchase only from suppliers providing third party heavy metal testing results
- Genuine shilajit should be a dark, tar-like resin that dissolves in warm water not a powder or capsule of unknown composition
- Avoid products without clear sourcing and testing documentation
- Purified shilajit (not raw shilajit) is the safer form
[🔵 Limited clinical evidence] for mitochondrial and testosterone effects. More human data than most substances in this article. Quality and heavy metal contamination are significant concerns sourcing is critical.
A Note on Low Dose Naltrexone (LDN)
Low dose naltrexone is covered in our main treatments article (Long Covid Treatments: What Actually Works?) rather than here, because it sits in a different category: it is a pharmaceutical drug used off label at low doses, prescribable by a GP in many countries, with a reasonable evidence base and an established safety profile. We mention it here because some Long Covid patients encounter it alongside the experimental substances in this article and may assume it belongs in the same category.
It does not. LDN has human trial data in Long Covid and related conditions, a known pharmacological mechanism, and can be accessed through a GP conversation rather than through research chemical suppliers. If you are interested in LDN, the starting point is a GP discussion not this article.
FAQs
Is it legal to buy these substances?
In most jurisdictions, research chemicals including peptides can be purchased legally for laboratory research purposes. The legal status of administering them to yourself is less clear and varies by country. In the UK, purchasing and possessing research peptides for personal use is generally not a criminal offence, but administering an unlicensed medicine to yourself exists in a regulatory grey area. This is distinct from the safety question something being legal to purchase does not make it safe to administer.
Where do Long Covid patients access these substances?
Most are purchased from research chemical suppliers online. Quality varies significantly. Some Long Covid patients access thymosin alpha-1 through private clinics or via travel to countries where it is an approved pharmaceutical. A small number of integrative medicine practitioners prescribe or supervise some of these substances with the caveat that this practice is outside standard medical guidelines.
Have any of these harmed Long Covid patients?
Serotonin syndrome cases involving methylene blue combined with antidepressants have been documented in the general medical literature not specifically in Long Covid patients but the risk is the same. Other adverse effects from the peptides in this guide have not been widely reported in Long Covid communities, though the absence of reporting does not mean the absence of harm adverse effects in self medication contexts are significantly underreported.
Are there clinicians who will supervise this?
Some integrative medicine practitioners and private clinics will discuss and sometimes supervise these substances. Standards vary significantly. A clinician who will prescribe or supervise experimental treatments without a thorough review of your medications (particularly for methylene blue), a full medical history, and a clear understanding of the evidence base is not providing adequate oversight. The right response to “can I try this” should involve a full conversation, not a quick yes.
Further reading: Long Covid Supplements: What the Evidence Actually Shows | Herbal Medicines and Long Covid | Long Covid Treatments: What Actually Works? | Long Covid FAQ
Disclaimer
This article is provided for educational and informational purposes only and should not be taken as medical advice. The substances discussed are not approved for the treatment of Long Covid, and many are not approved for human use in most countries.
The information reflects the best available evidence at the time of writing, but research is evolving rapidly. What appears promising in laboratory or early clinical studies may not ultimately prove to be safe or effective in larger human trials.
If you are considering any experimental treatment, discuss it with a suitably qualified healthcare professional who understands your medical history, current medications and individual circumstances. Never stop, start or change prescribed treatments without medical advice.
LongCovidJourney does not recommend or endorse self-medication with unapproved substances, nor does it endorse any specific clinics, practitioners or commercial products.
References
- Altmann DM, Boyton RJ, et al. The immunology of long COVID. Nature Reviews Immunology. 2023.
- Davis HE, McCorkell L, et al. Characterizing Long COVID in an international cohort: 7 months of symptoms and their impact. EClinicalMedicine. 2021.
- Crook H, Raza S, et al. Long covid—mechanisms, risk factors, and management. BMJ. 2021.
- Nalbandian A, Sehgal K, et al. Post-acute COVID-19 syndrome. Nature Medicine. 2021.
- Gharebaghi N, et al. Repurposing methylene blue in the management of COVID-19: Mechanistic aspects and clinical investigations. Biomedicine & Pharmacotherapy. 2021.
- Ginimuge PR, Jyothi SD. Methylene blue: revisited. Journal of Anaesthesiology Clinical Pharmacology. 2010. (Still one of the best reviews covering pharmacology, indications and safety.)
- FDA Drug Safety Communication. Serious CNS reactions possible when methylene blue is given to patients taking certain psychiatric medications. U.S. Food and Drug Administration.
- Fiorelli A, et al. Postoperative serotonin syndrome following methylene blue administration. Seminars in Cardiothoracic and Vascular Anesthesia. 2021.
- Goldstein AL, et al. Thymosin alpha 1: biological activities, clinical applications and future directions.(Comprehensive review.)
- Systematic Review and Meta-analysis: Thymosin α1 use in adult COVID-19 patients. International Immunopharmacology. 2023.
- Sikiric P, et al. Stable gastric pentadecapeptide BPC 157: review of experimental evidence and potential therapeutic applications. (Comprehensive review.)
- Keshri AK, et al. LL-37, the master antimicrobial peptide: from combating infections to immune regulation.International Journal of Antimicrobial Agents. 2024.
- Carrasco-Pozo C, et al. Shilajit: a natural phytocomplex with potential therapeutic properties. (Comprehensive review.)
- World Health Organization. WHO Good Manufacturing Practices (GMP) for pharmaceutical products.
- European Medicines Agency (EMA) or MHRA guidance on unlicensed medicines and pharmaceutical quality standards.