Thymosin Alpha-1
Approved somewhere, not everywhere.
Thymosin alpha-1 is approved as a medicine in a number of countries and is not approved in the United States, which makes its status harder to summarise than most.
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The science
A status that depends where you are
01
Thymosin alpha-1, also called thymalfasin, is a peptide derived from a thymic protein. It is approved as a medicine in a number of countries, where it has an approved indication and a label, and it is not approved in the United States.
02
That split makes it awkward to describe accurately. It is neither a pure research chemical like TB-500 nor an approved domestic product like tesamorelin, and a summary that picks one of those framings is wrong for half its readers.
03
The practical consequence is that where an approved product exists, its own instructions specify the diluent and the volume, and those take precedence over any general rule. Where it does not, there is no authoritative dose to consult at all.
04
The arithmetic is the same either way. A 5 mg vial reconstituted with 2 ml is 2.5 mg per ml, so a 1.6 mg dose is 0.64 ml, which is 64 units on a U-100 barrel. Milligram-scale doses fill the syringe quickly, so a dilute reconstitution runs out of barrel before it runs out of vial.
Lookup
5 mg and 10 mg vials by diluent volume
Doses are in milligrams, so they take a substantial share of the barrel. The table shows which reconstitutions keep them inside it.
5 mg Thymosin Alpha-1 vial
Units on a U-100 syringe
| Dose | 1 ml | 1.5 ml | 2 ml | 2.5 ml | 3 ml |
|---|---|---|---|---|---|
| 800 mcg | 16 | 24 | 32 | 40 | 48 |
| 1.6 mg | 32 | 48 | 64 | 80 | 96 |
| 3.2 mg | 64 | 96 | · | · | · |
| 5 mg | 100 | · | · | · | · |
10 mg Thymosin Alpha-1 vial
Units on a U-100 syringe
| Dose | 1 ml | 1.5 ml | 2 ml | 2.5 ml | 3 ml |
|---|---|---|---|---|---|
| 800 mcg | 8 | 12 | 16 | 20 | 24 |
| 1.6 mg | 16 | 24 | 32 | 40 | 48 |
| 3.2 mg | 32 | 48 | 64 | 80 | 96 |
| 5 mg | 50 | 75 | 100 | · | · |
A dot marks a combination that falls under two units or overflows a 100-unit barrel. Both are hard to measure accurately, so they are worth avoiding rather than eyeballing.
Regulatory status
Approved in some countries, not in the United States
Thymosin alpha-1, or thymalfasin, is approved as a medicine in a number of countries, where an approved indication and prescribing information exist. It is not approved by the FDA, so there is no United States label to consult.
Where an approved product is available, its own instructions are the authority on diluent, volume and dose, and they take precedence over anything on this page. Where it is not, material sold for research use carries no assurance of identity, purity or quantity.
Check the status in your own jurisdiction. A compound being approved somewhere is not the same as it being approved where you are, and this is one of the few cases where the honest answer genuinely differs by country.
FAQ
Common questions
How many units is 1.6 mg of thymosin alpha-1?
From a 5 mg vial reconstituted with 2 ml, the concentration is 2.5 mg per ml, so 1.6 mg is 0.64 ml, which is 64 units on a U-100 syringe. With 3 ml of diluent the same dose becomes 96 units, very close to the full barrel.
How much diluent should I use for a 5 mg vial?
If you have an approved product, use the volume its own instructions specify, because the stated dose assumes that concentration. Otherwise, 1 to 2 ml keeps milligram-scale doses inside a single 100 unit barrel; more than that and common doses will not fit.
Is thymosin alpha-1 approved?
It depends where you are. It is approved as a medicine in a number of countries, where it carries an approved indication and a label. It is not approved in the United States. Check the status in your own jurisdiction rather than assuming either answer applies.
Is it the same as thymosin beta-4 or TB-500?
No. Thymosin alpha-1 and thymosin beta-4 are different peptides with different sequences and different regulatory histories, and the shared name is misleading. TB-500 is a fragment related to thymosin beta-4 and is not approved anywhere.
Why does my dose take up most of the syringe?
Because the doses are in milligrams rather than micrograms. One hundred units is one millilitre, so a 1.6 mg dose at 2.5 mg per ml is already two thirds of the barrel. A more concentrated reconstitution brings it down, within what the vial will physically hold.
Sources
Where this comes from
Regulatory status and approved dosing are quoted from the primary source rather than summarised from memory. Each link below says what it is being cited for.
- Drugs@FDA: FDA-Approved DrugsU.S. Food and Drug AdministrationApproval status and approval history for any drug marketed in the United States.Link checked 1 October 2026
- DailyMedU.S. National Library of MedicineCurrent FDA-approved prescribing information, which is the authority on any approved dose.Link checked 1 October 2026
- Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C ActU.S. Food and Drug AdministrationThe three-category framework FDA applies to substances nominated for pharmacy compounding.Link checked 1 October 2026
VialClock
This page calculates. Your notes app forgets.
Every tool here is stateless by design. What it cannot do is remember that your vial was mixed eleven days ago, or that a step-up is due this week.
This tool performs arithmetic on figures you enter, or presents a manufacturer-published schedule. It does not know your protocol, will never suggest a dose, and is not medical advice. Dosing decisions belong with a qualified prescriber.