TB-4 vs TB-500 — Clearing Up the Confusion

Today we’re tackling a question I hear all the time: What’s the difference between thymosin beta-4 and TB-500? These two names often get tossed around like they’re the same thing — but they’re not. I’ve touched on this before, but because it can get pretty confusing, I want to break it down in more depth today.

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We’ll break down how each peptide works, the potential benefits and side effects we know about, what their half-lives look like, and why dosing often ends up being two to three times a week — even though technically you could dose daily at lower amounts. 

I also want to note that we’ll talk specifically about subcutaneous use, since that’s how these peptides are most often used in practice.

What is Thymosin beta-4 and TB-500? 

Let’s start simple.

Thymosin beta-4, or Tβ4, is the full-length natural peptide — it’s 43 amino acids long, and your body actually makes it. You’ll find it in platelets, white blood cells, and tissues all over the body. It helps with wound healing, new blood vessel growth, reducing inflammation, and keeping cells moving where they need to go.

On the other hand, TB-500 is a synthetic (man-made) fragment of Tβ4 — basically, chemists figured out that a small part of the Tβ4 sequence, specifically the section that binds actin, or the 17-23 fragment, that seemed to carry a lot of the healing and regenerative activity. 

The tricky part is, TB-500 isn’t always just that one fragment. Let me try to explain this very confusing concept. 

Most of the time, when people say TB-500, they’re talking about the 17–23 fragment — the piece linked to actin binding and tissue repair. But full-length thymosin beta-4 can actually break down into several different active fragments, like Ac-SDKP, the 1-4 section, the 4-10 section, and even the 20–35 region — and each of those has its own unique effects on healing, inflammation, or fibrosis. Something we can discuss in another podcast. 

The focus today will be on the full-length, naturally occurring 43-amino acid peptide and the common N-acetylated 17-23 fragment often referred to as TB-500.

So think of it this way: Tβ4 is the whole book, TB-500 is one powerful chapter.

How does thymosin beta-4 and TB-500 work?

Both thymosin beta-4 and TB-500 are best known for their role in tissue repair and recovery — but the way they work isn’t identical.

They both help guide cells to where they’re needed after an injury, a process called cell migration. They also help prevent or limit scar tissue, improve blood flow by encouraging angiogenesis — the growth of new blood vessels — and help settle down excessive inflammation so healing can happen.

Where they start to differ is in their scope.

The full-length thymosin beta-4 is like the master version. Because it’s the entire 43–amino acid chain, it has more binding sites and interacts with more pathways. That gives it a broader range of effects — it’s been studied not just for wound healing, but also for heart repair after a heart attack, corneal healing in eye injuries, nerve and brain protection after trauma, and even immune system modulation.

TB-500, on the other hand, is a synthetic fragment that contains the ‘active core’ sequence responsible for actin binding. This means it still boosts cell migration and new blood vessel growth, which are huge for recovery, but it doesn’t have all the extra regulatory sections of the full Tβ4 molecule. Because of that, TB-500 tends to be seen as more targeted — very good at tissue and tendon repair, wound closure, and improving circulation, but without the same wide-ranging effects on the heart, brain, or immune system that you see with the complete Tβ4 peptide

Half-Life and Dosing

 Okay, let’s talk about half-life, because this confuses people all the time.

Tβ4 has a short plasma half-life in humans — about one to two hours after IV dosing. That sounds super quick, right? But here’s the kicker: just because it clears from the blood doesn’t mean the effects are gone. Once it gets into tissues, it kicks off repair programs that can last for days.

TB-500 hasn’t been studied as thoroughly in humans, so we don’t have published plasma half-life numbers you can point to. What we do know from animal and lab st