Thymosin Alpha-1: Reference Overview and Reconstitution Notes

July 9, 2026

Thymosin Alpha-1

What it is

Thymosin Alpha-1 is a synthetic 28-amino-acid peptide corresponding to a fragment originally isolated from thymosin fraction 5 of the thymus gland. It belongs to the thymic peptide family, a group of naturally occurring signaling molecules associated with the thymus and the maturation of immune cells.

Research context and categorization

Thymosin Alpha-1 is generally grouped under the immune category, alongside related thymic peptides such as thymalin and thymulin. It is commonly discussed in relation to immune modulation, and in laboratory and clinical literature it has been investigated for its role in the differentiation of precursor T-cells into mature T-cells.

Beyond that, it is studied in the context of viral conditions such as hepatitis B and hepatitis C, as an adjunct in oncology-related immune support, and in relation to sepsis and infectious-disease immune response. It has also been examined in the context of anti-aging and general immune resilience. In roughly three dozen countries the peptide (marketed as Zadaxin) is an approved pharmaceutical for certain of these indications. In the United States, however, it is not FDA-approved, so any research uses described here should be understood as investigational and not confirmed or approved outcomes.

Status

Regulatory status: Research-only in the United States, not FDA-approved. It is approved as a pharmaceutical drug in a number of other countries for specific indications such as hepatitis B and hepatitis C. In the U.S. it has moved between FDA compounding categories, and its compounding status has been subject to regulatory changes.
Sport status: Not specifically listed on the WADA Prohibited List. Note that this differs from the related peptide Thymosin Beta-4 (and derivatives such as TB-500), which falls under the prohibited category of growth factors and growth factor modulators. Athletes should always confirm current status with their own governing body, since interpretation can fall under the non-approved-substances provision (S0) and lists are updated periodically.

Reconstitution notes (general)

Thymosin Alpha-1 typically ships as a lyophilized (freeze-dried) powder that is reconstituted with bacteriostatic water before use. The resulting concentration is simply the milligrams in the vial divided by the millilitres of bacteriostatic water added. For example, a 5 mg vial mixed with 2.5 mL of water yields 2 mg/mL. To convert a target measurement into a volume without doing the arithmetic by hand, use the calculator at /pages/tools.

Dilution and handling notes (compound-specific)

Common vial sizes are 5 mg and 10 mg. Typical reconstitution volumes fall in the roughly 1 mL to 3 mL range per vial, chosen to land on a convenient concentration. A 5 mg vial is often brought up with about 2.5 mL to 3 mL of bacteriostatic water (roughly 1.67 mg/mL to 2 mg/mL), and a 10 mg vial with about 2 mL to 3 mL (roughly 3.3 mg/mL to 5 mg/mL). The volume is selected mainly for ease of measurement rather than any chemical constraint.

Thymosin Alpha-1 is highly water-soluble and generally dissolves readily into a clear, colorless solution. It does not typically gel, cloud, or precipitate at the concentrations used above, so it is one of the more cooperative peptides to put into solution. Because it is a fairly delicate peptide, the practical handling quirk is mechanical: rather than firing the water stream directly onto the powder pellet, direct the water gently down the inner glass wall of the vial and let it run over the powder, then let it stand and swirl slowly instead of shaking. Shaking whips air into the solution, produces foam, and can promote aggregation. If any material remains undissolved, gentle swirling and a short rest usually completes it without added heat. The reconstituted solution is also treated as light-sensitive, which is why it is stored protected from light.

Handling and storage

Store reconstituted Thymosin Alpha-1 refrigerated at 2 to 8 degrees Celsius, kept out of direct light. Wipe the stopper with an alcohol swab before drawing, and label the vial with the mix date so the age of the solution is always clear. A reconstituted vial is generally considered usable for roughly a four-week refrigerated window; some references suggest an even shorter window, so err conservative. Avoid freeze-thaw cycles. Discard the solution if it turns cloudy or discolored, or if visible floaters or particulates appear.

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.