Thymalin: Reference Overview and Reconstitution Notes

July 9, 2026

Thymalin

What it is

Thymalin is a polypeptide complex originally isolated from the thymus tissue of young calves, made up of a mixture of short, low-molecular-weight peptides. It belongs to the group of thymus-derived peptide bioregulators, sometimes called cytomedins, associated with the Russian bioregulator tradition of Vladimir Khavinson. This is a neutral reference entry describing its identity, regulatory status, and general handling, not a usage guide.

Research context and categorization

Thymalin is generally categorized as an immune peptide, or thymic bioregulator. The thymus is the organ where T lymphocytes mature, and thymalin is commonly discussed in relation to that process. In the research and clinical literature, largely from Russia and Eastern Europe, it has been studied in the context of immune status regulation, T-cell differentiation, recovery of immune function after infection or other stress, and, within the broader Khavinson bioregulator framework, aging and longevity.

These uses should be read as investigational. Much of the supporting work comes from studies conducted in a single regulatory region, and large independent trials elsewhere have not confirmed a reliable, generalizable effect. Outside the specific indications approved in the countries where it is registered as a medicine, the effects described are not confirmed or approved benefits, and the compound is not established as a treatment for any condition in the United States.

Status

Regulatory status: Research-only in the United States. Thymalin is not approved by the FDA for any indication and has not been reviewed by the agency, so domestically it is available only as a research compound labeled not for human use. It has a long history as a registered immunomodulatory medicine in Russia and Kazakhstan, but that approval does not extend to the United States or the European Union.
Sport status: Not specifically listed on the WADA Prohibited List. Thymalin is an immunomodulatory thymic peptide rather than a growth factor or growth-hormone secretagogue, and it is not named among the peptide hormones, growth factors, or related substances in Section S2. Immunomodulators as a class are not broadly banned. Athletes should still verify the current list directly, since a substance can fall under a general category even when not named, and formulations vary.

Reconstitution notes (general)

For a lyophilized peptide supplied as a dry powder, the working concentration is simply the milligrams of compound in the vial divided by the millilitres of bacteriostatic water added. For example, 10 mg of powder plus 2 mL of water gives 5 mg/mL. A reconstitution calculator is available at /pages/tools to check the math before adding liquid.

Dilution and handling notes (compound-specific)

Thymalin is supplied as a lyophilized powder in sealed vials, commonly in 10 mg, 20 mg, and 50 mg sizes, and is reconstituted before use. A frequently referenced approach is to add roughly 2 mL of bacteriostatic water to a 10 mg vial for a 5 mg/mL solution, though the water volume is a matter of preference and can be adjusted to whatever concentration is convenient for a given vial size. Bacteriostatic water is the usual choice because the small amount of benzyl alcohol it carries limits microbial growth in a multi-use vial, which matters across a refrigerated storage window.

As a mixture of short peptides, thymalin generally goes into solution readily and yields a clear, colorless liquid without the persistent gelling or heavy precipitation seen with some larger or more hydrophobic peptides. To keep it that way, the water is best added slowly down the inside wall of the vial rather than squirted directly onto the powder, and the vial is then left to dissolve on its own or swirled gently. Vigorous shaking is avoided because it whips air into the solution and produces foam, which is both a sign of agitation stress and a nuisance when measuring an accurate volume. If any material stays undissolved, a few minutes at room temperature with gentle swirling usually finishes the job. A properly reconstituted solution should be completely clear; anything that turns cloudy, develops floating particles, or changes color is treated as compromised and not used.

Handling and storage

Store the reconstituted vial refrigerated at 2 to 8 degrees Celsius and keep it out of direct light. Wipe the rubber stopper with an alcohol swab before each puncture, and label the vial with the date it was mixed. Observe the general refrigerated window of roughly four weeks for a reconstituted peptide, and discard any vial that looks cloudy, discolored, or has visible floaters.

Tools and supplies

For laboratory and research reference only. Educational content, not medical, dosing, injection, or therapeutic guidance, and not intended for human or animal use. Any research uses described are investigational and not confirmed or approved benefits. Confirm anything involving health with a licensed professional. References linked above.