Thymalin

Thymalin is a polypeptide complex derived from calf thymus glands that functions as a potent immunomodulator and geroprotector, primarily used to restore immune function, support healthy aging, and enhance T-cell immunity. Popular among longevity enthusiasts, biohackers, and individuals seeking immune system support—particularly older adults experiencing age-related thymic involution—Thymalin is typically administered at 5–10 mg daily via intramuscular injection for 5–10 consecutive days, with courses repeated 1–2 times per year for ongoing immune maintenance.

What Is Thymalin?

Thymalin is a bioregulatory peptide complex first isolated from calf thymus tissue in 1981 by Russian researchers V.G. Morozov and V.Kh. Khavinson at the St. Petersburg Institute of Bioregulation and Gerontology. The drug is registered in Russia (registration number LS-000267) and has been used clinically for over four decades in the treatment of various immunopathologies, viral and bacterial infections, and age-related immune decline.

What makes Thymalin unique among peptide therapeutics is its composition of multiple bioactive short peptides, including the dipeptides EW (glutamic acid-tryptophan, also known as Thymogen), KE (lysine-glutamic acid, also known as Vilon), and the tripeptide EDP (glutamic acid-aspartic acid-proline, also known as Crystagen). These constituent peptides work synergistically to regulate gene expression, modulate cytokine production, and support the differentiation of immune cells.

The primary human-use benefits of Thymalin include:

• Restoration of T-cell and B-cell lymphocyte populations
• Enhancement of natural killer (NK) cell activity
• Normalization of the CD4+/CD8+ T-cell ratio
• Reduction of pro-inflammatory cytokines (IL-1α, IL-6, IL-8, TNF-α)
• Support for healthy blood coagulation and fibrinolysis
• Geroprotective effects that may extend lifespan and reduce mortality in older populations

How It Works

Epigenetic Gene Regulation

Thymalin's constituent short peptides (EW, KE, EDP) can penetrate the cell nucleus and nucleolus, where they bind complementarily to specific DNA sequences and histone proteins. This binding alters gene expression patterns, affecting the synthesis of heat-shock proteins, cytokines, fibrinolysis system components, and proteins involved in cellular differentiation, proliferation, and apoptosis. The KE peptide, for example, has been shown to regulate the expression of genes including IGF1, FOXO1, TERT, and NFκB in human mesenchymal stem cells.

T-Cell Differentiation and Thymic Support

Thymalin directly supports the differentiation of hematopoietic stem cells into mature T-lymphocytes. Research demonstrates that Thymalin reduces the expression of CD44, CD117, and CD28 markers on hematopoietic stem cells, promoting their maturation into functional immune cells. This mechanism is particularly valuable for older individuals, as age-related thymic involution significantly impairs T-cell production and immune competence.

Cytokine Modulation and Anti-Inflammatory Effects

Thymalin prevents excessive inflammatory responses by reducing concentrations of pro-inflammatory cytokines including IL-1α, IL-6, IL-8, and TNF-α. This cytokine-balancing effect helps prevent the "cytokine storm" phenomenon observed in severe infections and contributes to the peptide's therapeutic utility in inflammatory conditions.

Hemostasis Regulation

Beyond immune modulation, Thymalin normalizes blood coagulation and fibrinolytic activity. Clinical studies have shown that Thymalin reduces fibrinogen levels and D-dimer concentrations while supporting healthy platelet function. This makes it potentially valuable in conditions associated with hypercoagulability.

Dosage Protocols

The standard clinical dosage of Thymalin is 5–10 mg administered daily for 5–10 consecutive days. In clinical trials involving severe COVID-19 patients, researchers used 10 mg daily for 10 days with positive outcomes.

Cycling guidelines typically recommend:

• Initial course: 10 mg daily for 10 days
• Maintenance: Repeat courses 1–2 times per year
• For immune support during illness: A 5–10 day course may be initiated at symptom onset
• Preventive use in older adults: Semi-annual or annual courses to maintain immune function

Some practitioners recommend spacing courses at least 4–6 months apart to allow the body's natural regulatory mechanisms to function between interventions.

How to Use / Administration

Thymalin is administered via intramuscular (IM) injection, which is the standard route established through decades of clinical use in Russia. The lyophilized powder must be reconstituted with sterile bacteriostatic water or 0.9% sodium chloride solution before injection.

Administration steps:

1. Reconstitute the lyophilized Thymalin powder with 1–2 mL of bacteriostatic water
2. Gently swirl (do not shake) until fully dissolved
3. Draw the appropriate dose into an insulin syringe
4. Inject intramuscularly into the deltoid, gluteus, or vastus lateralis muscle
5. Rotate injection sites to prevent tissue irritation
6. Administer once daily, preferably at the same time each day

Some users report subcutaneous administration as an alternative, though intramuscular injection remains the clinically validated route.

Results Timeline

Based on clinical observations and research data:

• Days 1–3: Initial immune cell activation begins; some users report subtle improvements in energy
• Days 5–7: Measurable increases in lymphocyte counts may begin; reduction in inflammatory markers
• Days 10–14: Significant improvements in T-cell, B-cell, and NK-cell populations; normalization of C-reactive protein and D-dimer levels
• Weeks 2–4: Full immune reconstitution effects become apparent; improved resistance to infections
• Months 1–6: Sustained immune benefits; reduced incidence of respiratory infections (studies show 2.0–2.4-fold reduction in acute respiratory diseases in elderly patients)

Long-term geroprotective effects, including potential mortality reduction, have been observed over 6-year follow-up periods in clinical studies.

Research Evidence

Thymalin has been the subject of extensive research, primarily conducted in Russia, with several peer-reviewed publications documenting its efficacy:

A 2021 randomized controlled trial published in Advances in Gerontology examined Thymalin in 80 older patients with severe COVID-19. Patients receiving Thymalin (10 mg/day for 10 days) showed significantly faster clinical improvement, higher rates of lymphocyte recovery (66.6% vs. 43.18%), and reduced hospital mortality (19.4% vs. 40.9%) compared to standard therapy alone.

Research published in Biology Bulletin Reviews (2021) detailed the molecular mechanisms of Thymalin, demonstrating that its constituent peptides regulate gene expression, stimulate stem cell differentiation, and reduce cellular apoptosis in lymphoid tissues.

Studies on the synthetic dipeptide L-Glu-L-Trp (Thymogen, derived from Thymalin) showed that it slows aging and inhibits spontaneous carcinogenesis in rats, with a 1.5-fold decrease in tumor incidence.

Clinical studies in elderly patients demonstrated that Thymalin reduced the incidence of acute respiratory infections by 2.0–2.4 times and contributed to reduced mortality over a 6-year observation period.

Stacking

Thymalin is commonly combined with other peptides for enhanced longevity and immune support protocols:

Thymalin + Epithalon: This combination addresses both immune function (Thymalin) and pineal gland/telomere support (Epithalon). Epithalon, another peptide developed by the same research group, has been shown to activate telomerase and extend lifespan in animal models. Together, they form a comprehensive anti-aging protocol.

Thymalin + Thymosin Alpha-1: For enhanced immune reconstitution, some practitioners combine Thymalin with Thymosin Alpha-1, another thymic peptide with well-documented immunomodulatory effects. This combination may provide synergistic benefits for immune-compromised individuals.

Thymalin + BPC-157: For individuals seeking both immune support and tissue healing, combining Thymalin with BPC-157 addresses multiple physiological systems simultaneously.

When stacking, it is advisable to introduce one peptide at a time to assess individual response before adding additional compounds.

Reconstitution, Storage & Prep

Thymalin is supplied as a lyophilized (freeze-dried) powder that requires reconstitution before use.

Reconstitution procedure:

1. Allow the Thymalin vial to reach room temperature
2. Using a sterile syringe, draw 1–2 mL of bacteriostatic water (preferred) or sterile 0.9% sodium chloride
3. Inject the diluent slowly down the inside wall of the vial, not directly onto the powder
4. Allow the solution to dissolve naturally; gently swirl if needed—never shake vigorously
5. The resulting solution should be clear and colorless

Storage guidelines:

• Unreconstituted powder: Store at room temperature (below 25°C/77°F) or refrigerated; protect from light
• Reconstituted solution: Refrigerate at 2–8°C (36–46°F); use within 14–21 days when reconstituted with bacteriostatic water
• Never freeze reconstituted Thymalin
• Discard any solution that appears cloudy, discolored, or contains particulates

Side Effects

Thymalin demonstrates an excellent safety profile with minimal reported adverse effects across decades of clinical use.

Reported side effects are rare and typically mild:

• Injection site reactions: Mild redness, swelling, or discomfort at the injection site
• Transient flu-like symptoms: Occasional mild fatigue or low-grade fever as the immune system activates
• Allergic reactions: Rare; individuals with known hypersensitivity to bovine-derived products should avoid Thymalin

Contraindications:

• Known hypersensitivity to thymic peptides or bovine-derived products
• Active autoimmune conditions requiring immunosuppression
• Pregnancy and breastfeeding (insufficient safety data)
• Organ transplant recipients on immunosuppressive therapy

An important feature of thymus preparations, including Thymalin, is their therapeutic safety—even long-term use does not typically cause significant side effects.

Legal Status / FDA

Thymalin is not approved by the U.S. Food and Drug Administration (FDA) for any medical indication. In the United States, it is available only as a research chemical and is not legally sold for human consumption.

In Russia, Thymalin is a registered pharmaceutical drug (registration number LS-000267) approved for clinical use in treating immunodeficiencies, viral and bacterial infections, and as supportive therapy during chemotherapy and radiation treatment.

The regulatory status varies by country:

• Russia: Approved pharmaceutical
• European Union: Not approved; available for research purposes
• United States: Not approved; research chemical only
• Other countries: Status varies; check local regulations

Individuals considering Thymalin should be aware that purchasing and using non-approved peptides carries inherent risks, including product quality concerns and lack of regulatory oversight.

Sports / WADA

Thymalin is not specifically named on the World Anti-Doping Agency (WADA) Prohibited List. However, athletes should exercise caution for several reasons:

1. Peptide hormones and their releasing factors are prohibited under Section S2 of the WADA Prohibited List
2. Thymic peptides with immunomodulatory effects could potentially fall under prohibited categories depending on interpretation
3. The 2026 WADA Prohibited List includes provisions for substances that affect immune function

Athletes subject to anti-doping regulations should consult with their sports federation and anti-doping authority before using Thymalin or any thymic peptide. The safest approach for competitive athletes is to avoid all non-approved peptides.

Conclusion

Thymalin represents one of the most extensively researched thymic peptide preparations, with over four decades of clinical use supporting its role as an immunomodulator and geroprotector. Its unique mechanism of action—working through epigenetic regulation of gene expression and direct support of T-cell differentiation—distinguishes it from other immune-supporting compounds.

The clinical evidence, particularly from Russian research institutions, demonstrates meaningful benefits for immune reconstitution, reduced infection rates, and potential mortality reduction in older populations. The favorable safety profile, with minimal reported side effects even during long-term use, makes it an attractive option for those seeking immune support.

However, prospective users should recognize that Thymalin remains unapproved by Western regulatory agencies, and the majority of clinical research originates from a single research group. While the existing evidence is promising, additional independent studies would strengthen the evidence base. As with any non-approved peptide, sourcing from reputable suppliers and proper storage and handling are essential for safety and efficacy.

FAQ

What is the difference between Thymalin and Thymosin Alpha-1?
Thymalin is a polypeptide complex containing multiple short peptides (EW, KE, EDP) isolated from calf thymus, while Thymosin Alpha-1 is a single 28-amino acid peptide. Both support immune function, but Thymalin's multi-peptide composition may provide broader regulatory effects. Thymosin Alpha-1 has more extensive Western clinical trial data and is approved in some countries for hepatitis treatment.

How long do the effects of Thymalin last after a course?
Clinical observations suggest that immune benefits persist for several months following a standard 10-day course. Most protocols recommend repeating courses 1–2 times annually to maintain optimal immune function, particularly in older individuals.

Can Thymalin be used during an active infection?
Research, including the COVID-19 clinical trial, suggests Thymalin may be beneficial during active infections by supporting immune cell recovery and reducing inflammatory markers. However, this should only be considered under medical supervision, and Thymalin should not replace standard medical treatment.

Is Thymalin safe for individuals with autoimmune conditions?
Thymalin should be avoided in individuals with active autoimmune conditions requiring immunosuppression, as its immunostimulatory effects could potentially exacerbate autoimmune activity. Consultation with a healthcare provider is essential before use.

What is the best time of day to administer Thymalin?
There is no established optimal time for Thymalin administration. Most protocols recommend consistent daily timing. Some practitioners suggest morning administration to align with natural circadian immune rhythms, though clinical studies have not specifically addressed timing.

Can Thymalin be taken orally?
Thymalin is designed for intramuscular injection. While some constituent peptides (like the KE peptide in Crystagen form) have been studied for oral administration, the standard Thymalin preparation requires injection for proper absorption and efficacy.

How does Thymalin compare to Thymogen?
Thymogen is a synthetic dipeptide (EW/glutamic acid-tryptophan) that was isolated from Thymalin and represents one of its active components. Thymalin contains Thymogen plus additional bioactive peptides (KE, EDP), potentially offering broader effects. Studies show Thymalin has more pronounced effects on lymphoid tissue than individual short peptides alone.

Are there any drug interactions with Thymalin?
No significant drug interactions have been reported in the literature. However, caution is advised when combining Thymalin with immunosuppressive medications, as the peptide's immunostimulatory effects may counteract immunosuppressive therapy. Always disclose all medications to your healthcare provider.

References

1. Khavinson VKh, Linkova NS, Chalisova NI, Ivko OM. The Use of Thymalin for Immunocorrection and Molecular Aspects of Biological Activity. Biol Bull Rev. 2021;11(4):377-382. https://pmc.ncbi.nlm.nih.gov/articles/PMC8365293/
2. Kuznik B, Khavinson V, Shapovalov K, et al. Peptide Drug Thymalin Regulates Immune Status in Severe COVID-19 Older Patients. Adv Gerontol. 2021;11(4):368-376. https://pmc.ncbi.nlm.nih.gov/articles/PMC8654498/
3. Tuthill C, Rios I, McBeath R. Review of Thymic Peptides and Hormones: From Their Discovery to Clinical Applications. Protein Pept Lett. 2024. https://link.springer.com/article/10.1007/s10989-024-10666-y
4. Romani L, Bistoni F, Gaziano R, et al. Thymosin alpha 1: A comprehensive review of the literature. Expert Opin Biol Ther. 2020. https://pmc.ncbi.nlm.nih.gov/articles/PMC7747025/
5. Goldstein AL, Goldstein AL. Natural and synthetic thymic peptides as therapeutics for immune dysfunction. Int J Immunopharmacol. 1997. https://www.sciencedirect.com/science/article/pii/S0192056197000581
6. World Anti-Doping Agency. The Prohibited List 2026. https://www.wada-ama.org/en/prohibited-list
7. Anisimov VN, Khavinson VKh. Peptide bioregulation of aging: results and prospects. Biogerontology. 2010;11:139-149.
8. Khavinson V, Linkova N, Diatlova A, Trofimova S. Peptide regulation of cell differentiation. Stem Cell Rev Rep. 2020;16:118-125.
9. Khlystova ZS, Kalinina II, Shmeleva SP. Thymalin in developing respiratory organs of human fetus. Bull Exp Biol Med. 2003;135:600-602.
10. Paragon Sports Medicine. Thymalin Peptide Information. https://www.paragonsportsmedicine.com/peptides/thymalin