What is the difference between Splenin and Thymalin?

Splenin: Spleen-derived tetrapeptide bioregulator; normalizes leukocyte and platelet production; modulates splenic immune cell activity Thymalin: Thymic peptide bioregulator; restores thymic function and T-cell production; modulates cytokine balance; shown to extend lifespan in animal models

Is Splenin FDA approved?

Splenin is not evaluated or approved by the FDA. It is discussed for research and educational purposes only, not as medical guidance.

Is Thymalin FDA approved?

Thymalin is not evaluated or approved by the FDA. It is discussed for research and educational purposes only, not as medical guidance.

How is Splenin administered in research settings?

In research settings, Splenin is typically administered via the subcutaneous or intramuscular routes. PeptideBase does not provide dosing or administration instructions.

How is Thymalin administered in research settings?

In research settings, Thymalin is typically administered via the subcutaneous or intramuscular routes. PeptideBase does not provide dosing or administration instructions.

Home›Research›Compare›Splenin vs Thymalin

Peptide Comparison

Splenin vs Thymalin

Name: Splenin vs Thymalin — Per-mg Price Comparison
Creator: PeptideBase
License: https://peptidebase.io/terms

Both are Immune & Thymic peptides.

Splenin

Spleen peptide bioregulator

RecoveryNot EvaluatedResearch Only

Half-life: Unknown

1 providers listed

Full Splenin profile →

Thymalin

Thymus peptide

LongevityNot EvaluatedResearch Only

Half-life: Unknown

12 providers listed

Full Thymalin profile →

Bottom line

Thymalin is carried by more providers on PeptideBase (12 vs 1); otherwise the two are closely matched on the measures we track.

Quick Verdict

Splenin

Thymalin

Which One Should You Choose?

Your goal	Better option
Stronger clinical evidence	Thymalin
More provider options (1 vs 12)	Thymalin

Research summary only — not medical advice. Consult a qualified provider before making any decisions.

Side-by-Side Comparison

Splenin

Thymalin

Mechanism Family

Immune & Thymic

Half-life

Unknown

FDA Status

not evaluated

Admin Routes

subcutaneous, intramuscular

Availability

Research Only

Providers

1 listed

12 listed

Avail. Notes

Russian peptide bioregulator from spleen (Khavinson Institute). Immunomodulatory. No FDA approval, no NDA or IND. Not on any FDA list. Research chemical in US only.

Russian thymic peptide bioregulator (Khavinson Institute). Distinct from Thymosin Alpha-1. Not FDA-approved. Not on any FDA list. Research chemical in US.

Research Evidence

Splenin

Review · 2 key studies · most recent 2022

Thymalin

Review · 5 key studies · most recent 2023

Research Citations

Splenin

Review2022 · International Journal of Molecular Sciences

Neuroepigenetic Mechanisms of Action of Ultrashort Peptides in Alzheimer's Disease

Review2020 · Stem Cell Reviews and Reports

Peptide Regulation of Cell Differentiation

Thymalin

In vitro2023 · Int J Mol Sci

The Influence of KE and EW Dipeptides in the Composition of the Thymalin Drug on Gene Expression and Protein…

In vitro2020 · Bull Exp Biol Med

Thymalin: Activation of Differentiation of Human Hematopoietic Stem Cells.

Review1997 · Int J Immunopharmacol

Natural and synthetic thymic peptides as therapeutics for immune dysfunction.

In vitro2022 · Int J Mol Sci

Peptides Regulating Proliferative Activity and Inflammatory Pathways in the Monocyte/Macrophage THP-1 Cell Li…

+1 more

About Splenin

Spleen-derived tetrapeptide bioregulator; normalizes leukocyte and platelet production; modulates splenic immune cell activity

Research Areas

immune restorationblood cell productionsplenic function support

About Thymalin

Thymic peptide bioregulator; restores thymic function and T-cell production; modulates cytokine balance; shown to extend lifespan in animal models

Research Areas

immune restorationthymus function supportanti-agingimmune modulation

Safety Profile

Information below reflects published research data only — not medical advice. Consult a qualified provider before use.

Splenin

No established clinical contraindications. This is an investigational compound with limited human data and has not been evaluated by the FDA for safety in this context. Consult a qualified clinician.

Thymalin

Reported (Unverified — Pending Clinical Review)

autoimmune disease (use with caution)organ transplant (immunosuppression)

No established clinical contraindications

Price (per mg)

Splenin

Not enough vendor pricing yet.

Thymalin

$4.56/mg

$3.06 – $5.44 range

19 vendors

View price index →Find providers →

Find Providers

Where to source these peptides

Providers offering

Splenin

1 listed

Browse directory →

Providers offering

Thymalin

12 listed

Browse directory →

PeptideBase lists providers for educational research purposes only. Always consult a qualified healthcare professional before obtaining or using any peptide.

More Immune & Thymic Comparisons

Browse all peptides →

Educational research tools — not medical advice.

Cite this page

Data last updated August 26, 2026

Free to reference and republish with attribution to PeptideBase. Choose a format:

PeptideBase. (2026). Splenin vs Thymalin — Per-mg Price Comparison. Retrieved September 11, 2026, from https://peptidebase.io/peptides/compare/splenin/thymalin

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