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Some human trialsIn clinical trials

Thymosin beta-4

Also known as: Thymosin beta 4 · Tβ4 · TB4 · TB-4 · Full-length thymosin beta-4 · TMSB4X · RGN-259 · RGN-137 · NL005

Updated 26 sources

Thymosin beta-4 is the full 43 amino acid protein (about 4,963 Da) that cells use to hold actin in reserve for movement and repair. It has real human trials: IV safety studies, wound gels and eye drops. TB-500 is a 7 amino acid piece of it, and sellers use the names interchangeably. No trial has tested it as a subQ injection.
Calculate with Thymosin beta-4Dosage chart

Quick facts

Half-life
  • 0.5 to about 2 hours after IV recombinant thymosin beta-4 in healthy volunteers; no subQ data.
  • Rose with dose after IV synthetic thymosin beta-4 in healthy volunteers.
Routes
  • Intravenous (IV)
  • Topical
  • Subcutaneous injection
Forms
  • Vial (powder)
  • Topical
Reported dose ranges
  • 42 to 1,260 mg (intravenous (iv))
  • 0.05 to 25 mcg/kg (intravenous (iv))
  • 0.01 to 0.1% (topical)
  • 750 mcg (subcutaneous injection)
Vial sizes
  • 5 mg, 10 mg
Chemistry
  • 4,963 g/mol · C212H350N56O78S · CAS 77591-33-4
FDA status
  • In clinical trials
WADA
  • Prohibited

What people use Thymosin beta-4 for

  • Soft-tissue and injury recovery, as an alternative to TB-500
  • Wound and skin healing
  • Eye surface healing (dry eye, neurotrophic keratopathy) in trials
  • Heart repair after a heart attack, in IV trials
  • Hair regrowth and anti-scarring, from animal work

How it is thought to work. Thymosin beta-4 binds single actin units (G-actin) and releases them on demand, which lets cells rebuild their skeleton to crawl into a wound. Outside the cell it supports new blood vessels, cell survival and lower inflammation. Enzymes clip its first four residues into Ac-SDKP, which has effects of its own. In mice it activated ILK and Akt and improved heart function after injury.

Thymosin beta-4 dosing

10 protocols from studies, guides and community reports, grouped by goal. Tap a source badge to see where a number came from.

Intravenous (IV)4

IV safety study (synthetic protein)

Amount
42 to 1,260 mg
How often
One dose, then the same dose daily for 14 days
Route
Intravenous (IV)
Cycle
14 days
Timing and details

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IV single dose (recombinant NL005)

Amount
0.05 to 25 mcg/kg
How often
One dose
Route
Intravenous (IV)
Timing and details

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IV daily (recombinant NL005)

Amount
0.5 to 5 mcg/kg
How often
Once daily for 10 days
Route
Intravenous (IV)
Cycle
10 days
Timing and details

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IV after a heart attack (recombinant NL005)

Amount
0.5 to 1.5 mcg/kg
How often
First dose 12 hours after PCI, then daily on days 2 to 7
Route
Intravenous (IV)
Cycle
7 days
Timing and details

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Topical, topical2

Venous stasis ulcer gel (trial)

Amount
0.01 to 0.1%
How often
Once daily on the ulcer
Route
Topical, topical
Cycle
Up to 84 days
Timing and details

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Pressure ulcer gel (trial)

Amount
0.01 to 0.1%
How often
Once daily
Route
Topical, topical
Cycle
Up to 84 days
Timing and details

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Injected4

Guide convention (subQ)

Amount
750 mcg
How often
Twice weekly, Monday and Thursday (1,500 mcg a week)
Route
SubQ, vial (powder)
Timing and details

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Off-label loading (borrowed from TB-500)

Amount
2 to 5 mg
How often
Twice weekly
Route
SubQ, vial (powder)
Cycle
4 to 6 weeks, then weekly maintenance
Timing and details

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Off-label maintenance

Amount
2 to 2.5 mg
How often
Once weekly after loading
Route
SubQ, vial (powder)

Off-label high weekly

Amount
10 mg
How often
Once weekly for 6 weeks, then monthly
Route
SubQ, vial (powder)
Cycle
6 weeks, then monthly
Timing and details

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Doses shown are what sources report, labelled by origin. Not medical advice.

Full Thymosin beta-4 dosage guideEvery titration step in syringe units, missed doses and how to mix.

Vial strengths and syringe units

Every Thymosin beta-4 vial size with the water volumes sources use. Units are what to draw on a U-100 insulin syringe, worked out exactly.
Thymosin beta-4: concentration and U-100 syringe units for each vial size and water volume
WaterStrength750 mcgdose, units2 mgdose, units5 mgdose, units
5 mg vial
2 mLCompetitor guide2.5 mg/mL300.3 mL800.8 mL2002 mL2 draws
10 mg vial
2 mLCompetitor guide†5 mg/mL150.15 mL400.4 mL1001 mL
Units are on a U-100 insulin syringe (100 units = 1 mL). U-50 and U-30 barrels read the same units.† Water volume sourced for a different vial size. The math is exact either way.Water volumes from

Doses shown are what sources report, labelled by origin. Not medical advice.

Calculate with this peptideYour vial, your water, your dose: Thymosin beta-4 in syringe units, with the math shown.

Thymosin beta-4 side effects

What trials and labels report, kept apart from what users and guides report. Frequencies are worded as each source states them.

Reported in studies and labels3

From clinical trials and regulatory documents.

  • Adverse events in IV trials

    Infrequent, mild or moderate at 42 to 1,260 mg IV; mild to moderate with recombinant Tβ4. No dose-limiting toxicity or serious events in either.

  • Adverse events with topical gel

    Safety of all gel strengths acceptable and comparable to placebo in 73 venous ulcer patients

  • Adverse events with eye drops

    Safe and well tolerated in dry eye; no significant adverse effects in neurotrophic keratopathy

Reported by users and guides4

From community reports and dosing guides. Not measured rates.

  • Injection-site redness or irritation

    Typically mild, per one guide

    How people manage it

    • Rotate injection sites

  • Fatigue or mild headache

    Transient; reported by some users of the peptide class

  • Flu-like feeling

    Occasional, temporary

  • Eye stinging with drops

    Transient, on application

All 7 Thymosin beta-4 side effects and how people manage themEvery management tip, who should not use it, and side-effect questions.

Who should avoid it

  • Active or past cancerCondition

    Thymosin beta-4 drives cancer cell migration and metastasis in lab and tissue studies, and guides advise caution with any history of cancer. No human data.

  • Tested sportCondition

    Prohibited by WADA at all times under S2.3.

  • Pregnancy or breastfeedingCondition

    No safety data; guides say check with a clinician first.

Storage

Powder (before mixing)

Temperature
-20 °C

Freezer at -20 C. One seller states up to 24 months at -20 C. One guide says room temperature or fridge, away from light.

Mixed vial

Temperature
2 to 8 °C
Use within
7 to 10 days

Fridge at 2 to 8 C, use within 7 to 10 days, avoid freeze-thaw.

Mixed vial

Temperature
2 to 8 °C
Use within
30 days

Fridge at 2 to 8 C, use within 30 days, never freeze, per another guide.

Mixed with: Bacteriostatic water

Mixing. Water volumes for TB-500 vials are not assumed to apply. Check what your vial actually contains before using any TB-500 table.

Stacks people report

Combinations from guides and community posts, with the reason given.
  • BPC-157

    Used in place of TB-500 in a Wolverine-style stack with BPC-157. The pairing comes from TB-500 practice and has not been tested with the full protein.

Related versions

  • TB-500

    TB-500 is the 7 amino acid fragment Ac-LKKTETQ (residues 17 to 23). This entry is the full 43 amino acid protein. FDA's compounding list names only the fragment, and sellers use the two names interchangeably.

Compare Thymosin beta-4

Evidence and legal status

Evidence: some human trials

Real human trials, mixed results, none subQ. Two IV Phase 1 safety studies were clean. A venous ulcer gel Phase 2 showed a signal at 0.03%. Eye drops: a small dry-eye Phase 2 and a small keratopathy Phase 3 trended positive; a second keratopathy Phase 3 is recruiting. Recombinant IV Phase 2 trials in heart attack have completed without published results.

FDA and WADA

In clinical trials

Under FDA-regulated trials; not approved yet.

Not FDA approved. FDA's orphan database lists two designations for thymosin beta 4 (epidermolysis bullosa, 2004; neurotrophic keratopathy, 2013), both not approved. Eye-drop Phase 3 trials are running. FDA's compounding risk list names only the fragment, TB-500.

WADA 2026 S2.3 names thymosin beta-4 and its derivatives, such as TB-500, under growth factors, prohibited at all times. FDA's Category 2 page lists "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" among nominations withdrawn; the full-length protein is not named there.

WADA: Prohibited

Thymosin beta-4 questions

What is the difference between TB4 and TB-500?

TB4 (thymosin beta-4) is the full 43 amino acid protein, about 4,963 Da. TB-500 is a 7 amino acid fragment of it, Ac-LKKTETQ, about 889 Da. All the human trials used the full protein, and their doses do not transfer to the fragment.

Is my TB-500 vial actually thymosin beta-4?

It depends on the seller. Anti-doping chemists found the fragment in a TB-500 product, while at least one seller states its TB-500 is full-length, N-acetylated thymosin beta-4. The label alone does not tell you; a lab report that names the sequence or mass does.

Is TB4 Frag the same thing?

No. Products sold as TB4 Frag are usually Ac-SDKP, the first four residues of thymosin beta-4, which the body clips off the protein and which has effects of its own.

What doses did human trials use?

Three very different ranges: 42 to 1,260 mg IV daily for 14 days in a 2010 safety study; 0.5 to 5 mcg per kg IV daily in the newer recombinant programme; and gels of 0.01 to 0.1% or 0.1% eye drops applied to the wound or eye. None were subQ injections.

What subQ dose do people use?

No subQ dose has been tested. One guide uses 750 mcg twice weekly. Off-label protocols borrowed from TB-500 run 2 to 5 mg twice weekly for 4 to 6 weeks, then 2 to 2.5 mg weekly.

How do I mix a 5 mg vial?

One guide adds 2 mL of bacteriostatic water for 2.5 mg/mL, so 750 mcg is 30 units on a U-100 syringe. Use the calculator for other mixes.

What is the half-life?

In the recombinant IV study, terminal half-life ran from 0.5 to about 2 hours, peaking 3 to 15 minutes after the dose with no build-up over 10 days. In the synthetic IV study, half-life rose with dose. Nobody has measured it after subQ injection.

Does it work for wounds?

Early signals, no proof yet. In a venous ulcer trial, 0.03% gel looked most promising and about 25% of patients healed completely within 3 months. Gel trials in pressure ulcers and epidermolysis bullosa also ran.

Does it work for eyes?

Results are mixed. In a small Phase 3 in neurotrophic keratopathy, 6 of 10 treated eyes healed fully at 4 weeks versus 1 of 8 on placebo, a trend rather than a clear win. A competitor reports two large dry-eye Phase 3 trials missed their main goal. A second keratopathy Phase 3 is recruiting.

What are the side effects?

In trials, mild: IV doses up to 1,260 mg a day caused infrequent mild or moderate events with no serious ones, and gels and eye drops matched placebo. Guides list mild injection-site irritation, fatigue, headache and flu-like feelings for injected use.

Does it raise cancer risk?

There is no human evidence either way. It drives cancer cell migration and metastasis in lab and tissue work, so guides say avoid it with active or past cancer.

How long does mixed thymosin beta-4 last?

Keep it at 2 to 8 C. One guide says 7 to 10 days, another 30 days. Do not freeze it.

Is it FDA approved?

No. FDA's orphan database lists it for epidermolysis bullosa and neurotrophic keratopathy, both not approved. FDA's compounding risk list names only the fragment, TB-500.

Is it banned in sport?

Yes. WADA S2.3 names thymosin beta-4 and its derivatives, such as TB-500, prohibited at all times.

Ask about Thymosin beta-4

Answers come from this site's pages only, with a link to each source.

Sources

26 sources, each checked by date. Record updated Oct 24, 2026. Numbers are restated in our own words and labelled by where they came from.

Reference work2

  1. Thymosin beta-4Wikipedia · checked Oct 24, 2026
  2. Thymosin Beta 4, CID 45382195PubChem · checked Oct 24, 2026

Vendor guide1

  1. TB-500 10 mg product page (sold as full-length thymosin beta-4)Vendor product page · checked Oct 24, 2026

Competitor guide4

  1. Thymosin beta-4 protocol guidepathtopeptides.com · checked Oct 24, 2026
  2. Thymosin beta-4 research guidepeptidedeck.com · checked Oct 24, 2026
  3. TB-500 dosage chart (TB-500 vs thymosin beta-4)peptidedeck.com · checked Oct 24, 2026

Community-reported1

  1. Thymosin beta-4 report (off-label anecdotal protocols)outliyr.com, via a competitor guide · checked Oct 24, 2026