Peptide profile · Immune
Thymulin (FTS)
Zinc-dependent thymic hormone for immune restoration and T cell maturation
Written & reviewed by Michael Carroll · Research, Peptide Initiative
Typical dose
1-2 mg
Half-life
Approximately 2 hours
Bioavailability
Low oral bioavailability (injected administration required)
Molecular weight
858.9 g/mol
Evidence level
Limited human trials
01 · Compound profile
Scientific & efficacy data
Molecular formula
C33H54N12O15
Primary benefits
Thymulin directly promotes T cell differentiation and maturation, restoring healthy immune function in aged, malnourished, or immunocompromised individuals. Strong mechanistic basis in human cell research and extensive animal models.
Potent NF-κB and p38 MAPK inhibition reduces systemic inflammation and pro-inflammatory cytokines. Effective in animal models of lung disease with no reported toxicity. Mechanism well-characterized at molecular level.
Thymulin levels decline with age; supplementation can reverse thymic involution and restore immune competence in elderly populations. Supported by observational studies showing thymulin correlation with immune function across lifespan.
INSERM / Hôpital Necker, Paris, France
Amino acid sequence
pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn02 · Dosing
How much do I take?
1-2 mg · once daily (often dosed in the evening)
Subcutaneous injection: A small injection into the fatty layer just under the skin — the same way insulin is given.
Bioavailability High — most of the dose reaches your bloodstream, just more gradually than an IV.
Best time to take
Evening, preferably 6-8 PM to align with natural thymic hormone rhythm
With food?
Zinc supplementation should be taken with food if possible to improve absorption and reduce stomach irritation
If stacking
Separate thymulin injection from zinc supplement by at least 2 hours if supplementing with separate zinc dose. Can combine in reconstitution if using zinc-supplemented formulation.
+ Increase if
- +No adverse effects after 2 weeks at current dose
- +Minimal immune markers improvement (elevated CD4+/CD8+ ratio still low)
- +Thymulin antibody response not yet apparent
- +Tolerance and zinc status confirmed adequate
- Decrease if
- −Persistent local injection site reactions
- −Systemic symptoms (fever, malaise) beyond first week
- −Signs of immune overactivation (excessive inflammation)
- −Severe headaches or sleep disruption
✓ Signs of right dose
- ✓Improved CD4+ and CD8+ T cell counts
- ✓Reduced pro-inflammatory cytokine levels (IL-6, TNF-α)
- ✓Increased thymic output markers
- ✓Improved immune responsiveness to vaccines
- ✓Reduced frequency of infections
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03 · Suitability
Is this right for me?
Best for immune system restoration & t cell maturation in immunocompromised states
Best for
Age-Related Immune Decline
Thymulin levels naturally drop significantly in elderly populations. Supplementation can restore T cell maturation and immune responsiveness in aging. Research shows thymulin can reverse age-related thymic involution and restore helper/suppressor T cell balance.
Recovery from Severe Malnutrition
In severely malnourished individuals, the thymus shrinks and T cell development is impaired. In vitro studies show thymulin can restore T cell maturation even in those with thymic involution, making it useful in recovery protocols.
Chronic Inflammatory Conditions
Thymulin inhibits NF-κB activation and suppresses pro-inflammatory cytokines (IL-6, TNF-α, IL-8). Animal models show effectiveness in lung diseases, inflammatory pain, and neuroinflammation. Anti-inflammatory effects work through p38 MAPK suppression.
Consider alternatives if
Do not use if
Use with caution if
Not sure?
Compare Thymulin (FTS) with similar peptides to find the best fit for your goals.
04 · Administration
How do I use it?
Subcutaneous injection · Intradermal injection
Reconstitution — what you need
Example
If vial contains 1 mg (1000 mcg) thymulin: To achieve 250 mcg per injection, reconstitute with 4 mL bacteriostatic water, then draw 1 mL for 250 mcg dose.
Total mcg in vial ÷ Total mL reconstituted = mcg per mL. Then (Desired dose in mcg ÷ mcg per mL) = mL to draw.
Route
Subcutaneous injection
Best sites
Technique
- 01Clean injection site with alcohol prep pad, let dry 30 seconds
- 02Pinch skin fold to create mound
- 03Insert needle at 45-90 degree angle
- 04Push plunger slowly to inject peptide
- 05Withdraw needle and apply gentle pressure with gauze
- 06Rotate injection sites daily to avoid lipodystrophy
- 07Do not reuse needles
Storage · before reconstitution
Store lyophilized powder at 2-8°C (preferred) or 18-25°C in original sealed vial, protected from light and moisture. Do not freeze.
Storage · after reconstitution
Store reconstituted solution at 2-8°C in sterile vial or syringe. Keep sealed to prevent contamination. Use within 5-7 days.
Signs of degradation
Sample daily schedule
05 · Safety
Is it safe?
3 common side effects · 3 serious
Thymulin is a naturally occurring thymic hormone with favorable safety profile in research. No reported serious adverse events in animal models even at high doses. Limited human safety data but observed studies suggest good tolerability. Requires concurrent zinc supplementation for biological activity and additional safety assurance. Most concerns relate to immune overactivation in susceptible individuals, not direct peptide toxicity.
Safety data derives primarily from animal models and in vitro human studies. Direct human clinical trials are limited. Long-term safety profile in healthy volunteers not extensively documented. Use should be considered research-level, not FDA-approved therapeutic.
Common side effects · experienced by some users
Less common
These typically resolve with continued use or dose adjustment.
Stop and seek help if
- ×Severe allergic reactions or anaphylaxis
- ×Persistent fever above 101.5°F lasting more than 24 hours
- ×Severe joint or muscle pain unrelated to injection site
- ×Signs of autoimmune activation (rashes, persistent inflammation)
- ×Severe headaches or neurological symptoms
- ×Uncontrolled immune activation with systemic symptoms
- ×Pregnant status or planning pregnancy
- ×Development of new autoimmune disease symptoms
This information is for research purposes only. Stopping thymulin or any peptide should be discussed with a qualified healthcare provider. Do not discontinue abruptly without medical guidance. If experiencing emergency symptoms, seek immediate medical attention.
With other peptides
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With medications
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With supplements
- ✓
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06 · Effectiveness
How do I know it's working?
Limited human trials · first signs week 1-2
Evidence level
Limited human trials
How it works
Thymulin is a small hormone (nonapeptide) naturally made by your thymus gland, which is like your immune system's training center. It's the boss that tells immune cells how to develop properly and when to calm down inflammation. The catch: thymulin NEEDS zinc to work. Without zinc, it's like having the instruction manual but no batteries. As you age, your thymulin levels drop, which is why older people get sick more often. This peptide restores thymulin activity and helps your immune system remember how to fight infections and balance inflammation.
Thymulin (Zn-FTS) is a nine-amino acid peptide (pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) secreted by thymic reticulo-epithelial cells that acts as a thymic hormone essential for T lymphocyte differentiation and maturation. The zinc cofactor (Zn2+) is structurally integrated into thymulin's active site, essential for three-dimensional conformation and receptor binding. Mechanisms: (1) T Cell Maturation - Thymulin promotes transition of immature thymocytes to mature T cells by signaling through specific cell surface receptors, increasing both CD4+ helper T cells and CD8+ suppressor/cytotoxic T cells; (2) Anti-inflammatory Signaling - Thymulin inhibits NF-κB transcription factor activation, suppresses pro-inflammatory cytokine production (IL-6, TNF-α, IL-8), and suppresses p38 MAPK phosphorylation; (3) Immune Homeostasis - Thymulin maintains proper helper/suppressor T cell balance; dysregulation of this balance contributes to immunodeficiency and autoimmunity; (4) Neuroprotection - CNS microglia respond to thymulin signaling, reducing endotoxin-induced neuroinflammation through NF-κB inhibition; (5) Aging - Thymulin levels decline with age (~50% reduction by age 60), contributing to immune senescence; restoration of thymulin can reverse age-related thymic involution. Zinc deficiency reduces active thymulin bioavailability even if thymus production is normal, making zinc co-supplementation critical for efficacy.
What to expect
Week 1-2
What you might notice
- •Mild fatigue or 'immune activation' sensation
- •Possible transient headache or mild fever
- •Local injection site reactions (redness, swelling)
- •Sleep may feel deeper or dreams more vivid
What's normal
- •Mild systemic symptoms indicating immune mobilization
- •Local injection reactions lasting 1-2 hours
- •Temporary appetite changes
- •Slight elevation in body temperature
What's next
- →Continue current dose through week 2 to allow adaptation
- →Monitor for resolution of acute symptoms
- →Ensure zinc supplementation compliance (essential for activity)
- →Begin checking baseline immune markers if available
Week 2-4
What you might notice
- •Most acute symptoms resolve or significantly diminish
- •Improved energy levels and mental clarity
- •Reduced susceptibility to minor infections
- •Better wound healing and skin health
- •Improved sleep quality
What's normal
- •Continued minor injection site reactions (should be less pronounced)
- •Occasional transient headache
- •Lymph node palpability may persist (normal immune activation)
- •Gradual improvement in baseline immune function
What's next
- →Consider dose adjustment based on tolerance and immune response
- →Schedule immune function testing if available (T cell counts, cytokine panels)
- →Maintain zinc supplementation consistently
- →Evaluate effectiveness against baseline goals
Week 4-6
What you might notice
- •Measurable improvement in immune function markers
- •Significant reduction in infection frequency
- •Enhanced recovery from illness or injury
- •Improved inflammatory pain reduction (if high doses used)
- •Sustained energy improvement and immune resilience
What's normal
- •Minimal to no injection site reactions
- •Complete resolution of systemic symptoms
- •Persistent mild lymph node changes (can take weeks to normalize)
- •Stabilization at new immune homeostasis level
What's next
- →Complete final immune function testing
- →Evaluate goal achievement
- →Decide on continuation vs. cycling of thymulin
- →Consider maintenance dosing or discontinuation based on response
Signs it's working · Immune Function Markers
- ✓Increased CD4+ T cell count (absolute number increase of 200-500 cells/mm³)
- ✓Improved CD4+/CD8+ ratio toward healthy range
- ✓Reduced pro-inflammatory cytokines (IL-6, TNF-α, IL-8 decrease 20-50%)
- ✓Improved delayed-type hypersensitivity skin testing response
- ✓Increased thymic output markers (increased TREC counts)
Signs it's working · Clinical Outcomes
- ✓Reduced frequency of infections (fewer colds, respiratory infections, etc.)
- ✓Faster recovery from illness when infections occur
- ✓Improved vaccine response (better antibody titers)
- ✓Enhanced wound healing and recovery from injury
- ✓Reduced frequency or severity of inflammatory symptoms
Signs it's working · Subjective Health Markers
- ✓Sustained improved energy and reduced fatigue
- ✓Better immune resilience (feeling 'less prone to getting sick')
- ✓Improved sleep quality and immune consolidation
- ✓Reduced chronic inflammation symptoms
- ✓Improved recovery from physical exertion
Not seeing results? Common reasons
- •Inadequate zinc co-supplementation (thymulin requires zinc for biological activity; verify taking 15-30 mg daily)
- •Dose too low for individual immune status (may need adjustment upward after 2 weeks)
- •Reconstitution errors or improper storage (degradation reduces peptide activity)
- •Injection technique issues affecting bioavailability (ensure proper subcutaneous placement, not intramuscular or intradermal)
- •Short timeframe for assessment (immune restoration takes 3-4 weeks minimum; 6 weeks typical)
- •Underlying severe zinc deficiency or malabsorption preventing thymulin activation even with supplementation
Key research
07 · Questions
Frequently asked
Why is zinc so important with thymulin?+
Zinc is not optional—it's structurally part of thymulin's active form (Zn-FTS). Without adequate zinc, thymulin cannot bind to its receptors or exert any biological effect. This is why the research designation is 'Zn-FTS' (zinc-FTS). If you're deficient in zinc, thymulin supplementation alone won't work. You must take 15-30 mg elemental zinc daily. Zinc deficiency is also common in aging populations and malnutrition—exactly the groups that might benefit from thymulin.
What's the difference between thymulin and PAT (its analogue)?+
PAT is a synthetic analogue of thymulin that's designed to be more stable and potentially more potent. In research, PAT showed equal or stronger analgesic and anti-inflammatory effects than native thymulin at much lower concentrations. PAT may also have better shelf-life and stability. However, PAT has less clinical evidence than thymulin itself. If you can access PAT-based formulations, they may be preferable, but thymulin remains the most researched form.
How do I know if thymulin is working?+
The best measure is immune function testing: CD4+ T cell count, CD4+/CD8+ ratio, and pro-inflammatory cytokine levels (IL-6, TNF-α). These should show improvement by week 4-6. Clinically, you'll notice fewer infections, faster recovery from illness, better vaccine responses, and improved energy. If you don't have access to immune testing, track infection frequency, wound healing, and energy levels over 6 weeks.
Can thymulin cause immune overactivation or autoimmunity?+
Theoretically, yes—excessive immune activation could trigger or worsen autoimmune disease in susceptible individuals. This is why thymulin use requires caution in people with existing autoimmune conditions and why medical supervision is recommended. In research, no severe autoimmune reactions have been documented, but the risk exists. Start low, dose slowly, monitor closely, and stop if you notice signs of autoimmune flare (new rashes, persistent inflammation, joint pain).
How long do I use thymulin, and can I cycle it?+
Most research protocols use 4-6 week cycles. You could potentially cycle thymulin (e.g., 6 weeks on, 2-4 weeks off) to avoid tolerance or give your immune system recovery time. However, optimal cycling schedules haven't been formally studied. Some people use thymulin as a short-term immune restoration tool (one 4-6 week cycle) during aging or recovery from malnutrition. Consult with a healthcare provider about your specific situation.
Is thymulin FDA approved?+
No. Thymulin is a research compound without FDA approval in the United States. It exists in a gray zone: there are no direct clinical trials of native thymulin on ClinicalTrials.gov, only observational studies and extensive animal research. This means efficacy claims are based on preclinical data and in vitro human studies, not large-scale human trials. Use should be considered experimental and research-level.
Can I inject thymulin while taking immunosuppressive medications?+
Not without medical supervision. Thymulin is an immune activator, and immunosuppressive medications are designed to suppress the immune system. They work in opposite directions. If you're on immunosuppressants (for autoimmune disease, organ transplant, etc.), talk to your doctor before using thymulin. In some cases, low-dose thymulin under medical supervision might be possible, but it requires careful monitoring.
What happens if I stop thymulin suddenly?+
There's no withdrawal effect or rebound, but you'll lose the immune-boosting benefits over time. Thymulin has a short half-life (2 hours), so it clears quickly. If you were benefiting from immune restoration, stopping means those benefits fade. Whether to stop or cycle depends on your goals and immune status. Consult your healthcare provider before stopping.
Can I combine thymulin with other peptides like BPC-157 or Thymosin Alpha 1?+
Possibly, but this combination hasn't been well-studied. BPC-157 has complementary anti-inflammatory effects, so theoretically combining them makes sense. Thymosin Alpha 1 has similar immune-boosting properties, so combining might cause 'overdose' effects. If you're interested in combining peptides, do so under medical supervision and start with lower doses of each to assess tolerance and monitor immune markers closely.
08 · Further reading
History & related research
History · since 1977
A nine-amino-acid zinc-dependent peptide hormone produced exclusively by thymic epithelial cells that orchestrates T-cell differentiation and immune function.
A nine-amino-acid zinc-dependent peptide hormone produced exclusively by thymic epithelial cells that orchestrates T-cell differentiation and immune function. Discovered in 1977 by Jean-François Bach, thymulin has proven its power in treating rheumatoid arthritis, reversing age-related immune decline, and—through cutting-edge gene therapy—even reversing established allergic asthma.
Read the full history of Thymulin (FTS)