Recovery and tissue repair

TB-500

Seven amino acids cut from a 43 amino acid peptide

What it actually is

TB-500 is a short chain of seven of the building blocks the body uses to make proteins, put together in a lab. It is sold under the same name as thymosin beta-4, a natural substance found in most human cells that is 43 building blocks long, but TB-500 is only a small piece snipped out of the middle of it. Almost all the research people quote when they talk about TB-500 was run on the bigger natural one, not on the piece being sold.

What it is supposed to do

The larger natural version is described as working by grabbing hold of actin, a protein that gives cells their shape and lets them crawl toward a wound. Nobody has found the landing site on a cell that either molecule attaches to, and the way these substances act outside cells is described in the research as not known. For the seven building block piece sold as TB-500 there is no data of any kind on what it sticks to.

What people take it for

People take it hoping to heal faster from injuries, mostly muscle, tendon and joint damage. That is the use with the thinnest support behind it: a 2026 review that read through 1,772 records and kept 80 studies found muscle and joint work sparse, and found evidence on TB-500 itself in exactly one study.

The dose question

What circulates: 2 mg twice weekly, then weekly
What was studied: No human dose has ever been published; FDA found no article administering it to a human

There is nothing to compare against. Every mg/kg figure in circulation belongs to thymosin beta-4, which FDA states is not the same substance.

Reported because it is what people use. Nothing here recommends any amount.

How long it lasts

Nobody has measured this in a person. In rats it came apart fast, with one breakdown piece dominant in the first six hours and another still detectable at 72 hours.

Route studied

No published human use by any route. The larger natural version was given into a vein.

Route used

Under the skin, at home

How to check you have the right molecule

Compare the molecular weight on the certificate of analysis. What is actually sold as TB-500 has a formula of C38H68N10O14 and an average molecular weight of 889.0, exact mass 888.49, CAS number 885340-08-9. Real thymosin beta-4 is C212H350N56O78S with an average molecular weight of 4,963, about five and a half times heavier. If a vendor calls the product thymosin beta-4 and its own report lists a weight near 889, the report is describing the seven building block piece no matter what the marketing says. Two things that look wrong but are not: a measured peak near 889.5 next to a stated weight of 889.0 is normal, and net peptide content below 100 percent is expected because the powder carries salt and water.

Walked through on two real certificates in how to read a certificate of analysis.

What people get wrong

That TB-500 and thymosin beta-4 are the same substance. They are two different molecules, and borrowing the larger one's research history and its clean human safety record for the seven building block piece is the error that gets printed on the label and paid for at checkout.

What is known about harm

There are no recorded side effects of TB-500 in people, because no published report exists of anyone giving it to a person. There is also no safety testing in animals of any kind, not short term, not repeated dosing, not cancer, not effects on offspring, so the empty record means untested rather than clean. The nearest real cancer finding involved forcing already malignant melanoma cells to overproduce the full length natural version, which pushed lung tumour counts from 10.9 to 46.7, and that is a different thing from injecting the small piece.

The arithmetic

TB-500 is sold in 5 mg and 10 mg vials. Mixing errors put people an order of magnitude off using a perfectly good vial, and the arithmetic is simple enough to check yourself.

Vial	Water	Concentration	In 10 units
5 mg	1 mL	5 mg/mL	500 mcg
5 mg	2 mL	2.5 mg/mL	250 mcg
5 mg	3 mL	1.67 mg/mL	167 mcg
10 mg	1 mL	10 mg/mL	1 mg
10 mg	2 mL	5 mg/mL	500 mcg
10 mg	3 mL	3.33 mg/mL	333 mcg

10 units is 0.1 mL on a U-100 insulin syringe, whatever is in it. For any other combination, or to see the arithmetic worked out, use the calculator.

Everything on this page is a summary. The citations, the studies and the reasoning live in the full entry.

Read the full entry on TB-500

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