Thymulin Dosage Chart: 2mg/Day for 20 Days

Thymulin is a zinc-dependent nonapeptide hormone produced by thymic epithelial cells. It is the only thymic hormone with a fully characterized chemical structure, and it requires zinc for biological activity. As thymic function declines with age, circulating thymulin levels drop — becoming virtually undetectable by age 60.

Research-context information only. Thymulin is a research peptide. Protocols, doses, and reactions reported below come from published research and self-reported community sources. This article reports what has been documented, not what should be done. Consult a licensed physician for personal medical decisions.

No thymulin formulation is FDA-approved. All protocols below are derived from published research and community experience. This is not medical advice.

Quick Reference: Standard Protocol

Community protocols describe running 2 mg daily for 20 consecutive days, then stopping. Cycles repeat roughly 3 times per year (roughly every 4 months). Thymulin is biologically inactive without zinc, so protocols include zinc supplementation throughout. For the full thymulin profile, see our thymulin benefits and research guide.

Cycling Details

Unlike peptides that run 8-week cycles, thymulin uses shorter, concentrated 20-day bursts repeated 3 times annually. This provides focused immune support windows — the 20-day period is sufficient to promote T-cell maturation and immune recalibration.

Community protocols typically space cycles roughly every 4 months; practitioners describe this as providing focused immune windows with time between courses.

Zinc is critical: Thymulin exists as inactive apo-thymulin (peptide alone) and active zinc-thymulin (Zn-FTS). Without zinc, thymulin cannot interact with its T-cell receptor (Dardenne et al., 1994). Published protocols include 15–30 mg/day elemental zinc (picolinate, glycinate, or citrate) throughout each course. Research on zinc toxicity consistently documents that long-term intake above 50 mg/day risks copper depletion.

Routes of Administration

Subcutaneous (standard and only route): Trial protocols use subcutaneous injection into the lower abdomen, upper outer thigh, or back of upper arm, rotating sites. Community reconstitution guides reference 29–31 gauge, ½-inch insulin syringes. Community logs frequently report evening timing, citing alignment with sleep-phase immune activity.

Reconstitution Quick Reference

20 mg vial + 2 mL BAC water = 10 mg/mL. Your 2 mg dose is 20 units on an insulin syringe. One vial lasts 10 days — you need 2 vials per 20-day cycle.

Community protocols describe gentle swirling — not shaking — to avoid degradation, with storage at 2–8°C and use within 28 days.

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Where These Numbers Come From

Thymulin research spans several decades of immunology, though no large-scale clinical dosing trials exist comparable to thymosin alpha-1's dataset.

Zinc Dependency: Age-related thymulin decline is not solely due to reduced thymic production — it is partly driven by declining zinc availability in the thymic microenvironment (Mocchegiani et al., 1995). This is why zinc co-supplementation is considered essential.

Thymulin Structure: The 9-amino acid peptide (Glu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn) was fully characterized by Bach et al. (1989), establishing it as the only thymic hormone with a defined chemical structure (Bach et al., 1989).

Immune Function: Thymulin's primary role is T-cell differentiation and maturation at the thymic level. It acts upstream of thymosin alpha-1, which enhances mature T-cell function. The 20-day cycle length is described in research as consistent with T-cell maturation timelines, though no large-scale dosing trial has formally established it.

Stacking Protocols

Thymulin + Thymosin Alpha-1

Complementary mechanisms — thymulin develops T-cells, TA-1 activates them.

Thymulin + LL-37

Different arms of the immune system — adaptive vs innate.

Side Effects & Safety

• Injection site reactions — mild redness, pain, or swelling (transient)
• Mild fatigue — occasionally in the first few days
• Mild headache — infrequent
• Transient flu-like symptoms — rare, possibly indicating immune engagement
• No serious adverse events reported in thymulin research literature
• Zinc-related GI discomfort — nausea from zinc supplementation, take with food
• Contraindicated in active autoimmune disease, organ transplant recipients, and lymphoproliferative disorders

mg to Units Conversion

On a standard 100-unit insulin syringe, each "unit" equals 0.01 mL (so 100 units = 1 mL). Once thymulin is reconstituted, the conversion from a target dose to syringe units depends on the chosen dilution.

The two reconstitution ratios most often described in community protocols are below.

Reconstitution A: 20 mg vial + 2 mL BAC water (10 mg/mL) — the standard dilution from the Quick Reference above.

Reconstitution B: 20 mg vial + 1 mL BAC water (20 mg/mL) — less BAC water for a lower total volume, so smaller draws and less fridge space.

These conversions reflect the dilutions documented in community reconstitution protocols. They report how the math is described, not a recommended dosing schedule.