TB-500 Fragment 17-23
Taken for injury recovery
Thymosin β4 actin-binding region
Match every finding to its exact substance, formulation, route and study population. A related molecule or approved medicine does not validate a catalog vial.
Color key
At a glance
Why people take it. And what backs it up.
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Heal injuries faster
Lab and animal studies, mixed
Buyers inject it after muscle, tendon or bone injuries, hoping it heals like the full TB4 protein it comes from.
Sources (6)
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“I find that the isolated TB-500 fragment does a much better job at injury repair, than the full spectrum TB-4 that is used in blends.”
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“The first tb-500 vial I purchased was the frag 17-23 which was $66 for 10mg.”
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ForumReddit r/Peptides: same post (July 2024), what it is taken for (opens in a new tab)
“I’m currently taking bpc-157, tb-500, ghk-cu, Ipamorelin and CJC-1295 No Dac for tennis elbow, frozen shoulder and distal biceps tendonitis and for arthritis in my shoulder and hips.”
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“marketed online for use in a variety of conditions including promoting tissue repair and regeneration; healing damage to tendons, muscles, ligaments, and bones; wound healing, promoting angiogenesis; reducing inflammation”
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“a seven-amino acid synthetic peptide, LKKTETQ, was able to promote repair in the aged animals comparable to that observed with the parent molecule.”
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“TB-500 (free base) appeared to be devoid of wound-healing properties in an in-vitro study (Rahaman et al. 2024).”
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Evidence briefing
Sources checkedWhat the sources support.
The listed fragment is the seven-residue LKKTETQ sequence, while commercial and FDA use of TB-500 is inconsistent and cannot verify seller-vial contents. No human trial evidence for this exact fragment was identified. The 2026 PCAC recommendation is not drug approval.
FDA review of nominated TB-500 bulk forms does not establish identity or evidence for this exact fragment.
The research. What’s been studied.
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Animal & lab studies
Laboratory and animal research
The LKKTETQ sequence has been studied in preclinical work related to actin binding and cell migration; this does not establish human healing benefit.
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Unverified
Human evidence
No human clinical trial of the seven-amino-acid fragment was identified.
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Unverified
Name and identity
The name TB-500 is used inconsistently; a product label does not verify that a vial contains the exact fragment or a particular salt.
What do these labels mean?
- Human evidence: approved-drug data or larger human studies, within the populations and uses studied.
- Early human studies: small, preliminary or limited human studies.
- Animal & lab studies: animal or laboratory findings that do not establish effects in people.
- Unverified: a proposed use or claim without verified supporting clinical evidence.
How each claim was reviewed (3)
Reported effects and evidence.
A citation may support, qualify or correct a claim. Read the study scope; a laboratory result is not an established benefit in people. Each review covers a claim as it was first collected; the tiles above show the collection’s current wording.
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Preclinical fragment experiment
Review of “Wound closure”
A synthetic LKKTETQ fragment promoted dermal repair in aged mice; specify whether the marketed material is acetylated.
Limitations and applicability. Unacetylated LKKTETQ, acetylated TB-500 and full-length protein are not interchangeable evidence targets.
Original collected claim and review history
Original title: Wound closure
Carries much of thymosin beta-4’s wound-healing activity in lab and animal studies.
Original label: animal. Preserved for traceability; the reviewed wording above qualifies this record.
Record tb500-frag:benefit:1 · Annotated 2026-10-01 · Review method
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Structure/function evidence; exact fragment match needed
Review of “Cell migration”
LKKTETQ lies within the actin-binding region; exact isolated-fragment binding and migration claims need form-specific evidence.
Limitations and applicability. Full-length actin-binding maps do not establish biological behavior of every isolated/acetylated fragment.
Original collected claim and review history
Original title: Cell migration
Binds actin, helping repair cells move into an injury.
Original label: animal. Preserved for traceability; the reviewed wording above qualifies this record.
Record tb500-frag:benefit:2 · Annotated 2026-10-01 · Review method
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Preclinical sequence-dependent finding
Review of “Blood vessel growth”
Angiogenesis has been reported for related short sequences; retain the exact tested sequence alongside the claim.
Limitations and applicability. This source describes LKKTETQ plus an additional Q; do not silently assign it to the 17–23 heptapeptide.
Original collected claim and review history
Original title: Blood vessel growth
May promote new blood vessels in healing tissue.
Original label: animal. Preserved for traceability; the reviewed wording above qualifies this record.
Record tb500-frag:benefit:3 · Annotated 2026-10-01 · Review method
The research in detail
Evidence category
Mostly animal and cell studies
Preclinical studies examine the seven-amino-acid fragment or full-length thymosin beta-4, which are different substances. No human clinical trials of the exact fragment were identified.
Evidence is assessed claim by claim above. Regulatory approval, study design, findings and relevance are separate questions; there is no single evidence score.
Risks and unknowns. What to know first.
Collected cautions follow. These are not an exhaustive or independently validated safety assessment; claim references do not automatically support every caution.
- Human safety unknown.
- Same theoretical tumor concern as other blood-vessel-promoting peptides.
What people report
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Regulator
FDA says compounded thymosin beta-4 fragment (LKKTETQ, ‘TB-500’) may cause immune reactions and that it found no human exposure data, so it cannot know whether the drug harms people.
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Regulator
In July 2026 an FDA advisory committee voted 8–6 (one abstention) to recommend allowing TB-500 for compounding, for wound healing, against FDA staff advice. The vote is not binding.
Source: AJMC, FDA Panel Backs 6 Peptides for Compounding (July 2026) (opens in a new tab)
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Regulator
Thymosin beta-4 and its derivatives, naming TB-500, are banned in sport at all times (World Anti-Doping Agency category S2).
Source: World Anti-Doping Agency Prohibited List (opens in a new tab)
Show all 5 cautionsShow fewer cautions
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Study
FDA’s review found a lab study in which the fragment itself did not help cells close a wound, while one of its breakdown products did. FDA’s adverse-event database had no reports for TB-500.
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User reports
Users report mislabeling in both directions: vials sold as ‘TB4’ that tested as the fragment, and vials sold as ‘TB-500’ that tested as full-length thymosin beta-4. One user who realised his ‘TB-500’ was full-length TB4 believed he had overdosed.
Source: Reddit r/Peptides thread ‘Dosing for TB500 (not TB4)’ (opens in a new tab)
Published dosing records. No established dose.
Historical label and trial records for the named product, route, population and indication. These records are not a personal schedule or a validated regimen for a catalog vial. Source attribution does not establish applicability.
This 7-amino-acid piece of thymosin beta-4 (LKKTETQ) has only been studied in lab, animal and drug-testing work. The FDA says it has found no human exposure data, and no trial or label sets a dose.
Any dose you see online for it is a guess, not a tested dose.
Community protocols. Reported online. Not clinically validated.
Community reports Collection date: 30 Sep 2026People who knowingly buy the 17–23 fragment mostly inject 1–3 mg under the skin every day (a vocal minority uses 5–10 mg), while others keep the classic ‘TB-500’ schedule of about 2–3 mg twice a week.
More about this
Evidence is thin, mostly one long MESO-Rx thread and scattered Reddit posts, and sources often cannot tell the fragment from full-length thymosin beta-4.
Daily milligram dosing
Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.
- Forum: MESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025)
- Forum: MESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025)
- Forum: MESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025)
Frequency labels describe this collection, not a measured population. Contradictory records remain available.
Details and sourcesHide details
- Dose
- 1–3 mg a day (2 mg is often called the minimum that helps)
- How often
- Once a day, often in the morning
- Route
- Injection under the skin
- How long
- About 1 month, then a lower maintenance dose
- Ramp
- Some drop gradually from 2 mg to 1 mg to 500 mcg as pain improves
- Mixing
- Research vials (often 10 mg) mixed with bacteriostatic water; some want 30 mg of fragment plus BPC-157 in one 3 mL pen cartridge
- Forum users identify the real fragment by a lab test result of about 889 daltons and say most ‘TB-500’ vials test as full-length thymosin beta-4 instead.
- One poster argues 1 mg of fragment equals about 5 mg of full-length thymosin beta-4, based on molecular weight.
Sources (3)
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ForumMESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025) (opens in a new tab)
“zero sides, been on frag now for nearly a month straight, 1mg ED AM”
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ForumMESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025) (opens in a new tab)
“sweet spot for me is around 2mg, joints dont hurt at all, going lower they hurt. 3mg is best but atleast 2mg.”
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ForumMESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025) (opens in a new tab)
“Starting my experiment with 3mg/day of Tb500 frag”
Twice-weekly ‘TB-500’ schedule
Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.
- Forum: Reddit r/Peptides, thread ‘Dosing for TB500 (not TB4)’ (2025)
- Forum: Reddit r/Peptides, thread ‘I overdosed on TB 500 because it’s actually TB4’ (2025)
Frequency labels describe this collection, not a measured population. Contradictory records remain available.
Details and sourcesHide details
- Dose
- About 2–3 mg per shot; 4–8 mg a week
- How often
- 2–3 times a week
- Route
- Injection under the skin
- Users who keep this schedule say the fragment lasts longer in the body than full-length thymosin beta-4. Others say the fragment clears within hours and needs daily or several-times-daily doses.
Sources (2)
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ForumReddit r/Peptides, thread ‘Dosing for TB500 (not TB4)’ (2025) (opens in a new tab)
“A good dose for TB500 would be 2-3mg x2 week”
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“The guidelines for TB 500 is 4-8 mg per week divided over 2 to 3 doses.”
Show all 4 protocolsShow fewer protocols
High dose after surgery or serious injury
Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.
- Forum: MESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025)
- Forum: MESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025)
- Forum: Reddit r/Peptides, thread ‘Dosing for TB500 (not TB4)’ (2025)
Frequency labels describe this collection, not a measured population. Contradictory records remain available.
Details and sourcesHide details
- Dose
- 5–10 mg a day (or 2–3 mg three times a day)
- How often
- Once to three times a day; one poster suggests 2–10 mg every other day
- Route
- Injection under the skin
- How long
- Weeks, around surgery or until the injury settles
- Usually combined with similar milligram doses of BPC-157.
Sources (3)
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ForumMESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025) (opens in a new tab)
“I guess 6 mg of TB 500 frag and 6 mg of BPC 157 is doing the trick”
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ForumMESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025) (opens in a new tab)
“i suggest somewhere around 2-10mg eod depending on injury.”
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ForumReddit r/Peptides, thread ‘Dosing for TB500 (not TB4)’ (2025) (opens in a new tab)
“I like 2-3mg 3x day (that’s 6-9mg/day total). More is better with TB4 fragments.”
With ARA-290
Collected report · exact form and route are only as reported below. Source date and reporter identity are not separately verified. Collection checked 30 Sep 2026; presentation annotated 2026-10-01.
- Forum: MESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025)
- Forum: MESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025)
Frequency labels describe this collection, not a measured population. Contradictory records remain available.
Details and sourcesHide details
- Dose
- Fragment 2.5–5 mg a day plus ARA-290 2–4 mg a day
- How often
- Once a day
- Route
- Injection under the skin, in separate syringes
- How long
- About 1 month
- Users say ARA-290 should not be mixed in the same syringe as other peptides.
Sources (2)
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ForumMESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025) (opens in a new tab)
“5mg TB frag / 2mg ARA daily. Separate pins as you can’t mix ARA with anything.”
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ForumMESO-Rx forum, ‘A comprehensive tb500 frag thread’ (2025) (opens in a new tab)
“starting 4mg ARA and 2.5mg tb frag ED today.”
Where the numbers come from
There is no documented source. ‘TB-500’ began as a veterinary product for racehorses around 2011, which doping labs showed to be this acetylated 17–23 fragment. Today users either reuse the twice-weekly TB-500 schedule or convert full-length thymosin beta-4 doses by molecular weight. FDA says it found no human exposure data for this fragment.
Research notes
Which molecule a source means is often unclear. FDA and doping labs call this fragment ‘TB-500’, but most vendors sell full-length thymosin beta-4 under that name, so general ‘TB-500’ dosing advice (see the tb4 entry) may not apply here. Forum claims about the fragment’s half-life contradict each other (lasting days versus clearing within hours), which drives the split between twice-weekly and daily or several-times-daily dosing. The July 2026 FDA advisory vote on ‘TB-500’ concerned this fragment, not full-length thymosin beta-4. Almost all fragment-specific dosing comes from one 2025 MESO-Rx thread.
What it is. In plain English.
A seven-amino-acid fragment marketed as TB-500; human trial evidence for this exact fragment has not been established.
The site identifies this product as the seven-amino-acid sequence LKKTETQ, corresponding to positions 17–23 of full-length thymosin beta-4. The commercial name TB-500 is used inconsistently, so the label alone does not verify product identity.
Preclinical work proposes that the fragment can bind actin and affect cell movement. Human effects have not been established.
Reviewed 2026-10-01.
Structure. A close relative’s structure.
Related structure
The seven amino acids LKKTETQ (coral), which are amino acids 17–23 of thymosin beta 4, inside a longer piece of thymosin beta 4 (amino acids 4–25, gray) bound to skeletal-muscle actin (gray). A second actin molecule and the piece of the hybrid peptide bound to it are not drawn.
How it differs. This is not the 7-amino-acid fragment on its own, which has no structure. It is a stretch of thymosin beta 4 inside an engineered hybrid peptide, crystallized with rabbit actin (rabbit and human skeletal actin have identical sequences).
4PL8, Xue et al., 2014. Rendered with Mol* (Sehnal et al., 2021) from RCSB PDB data (Berman et al., 2000).
Specs. The facts at a glance.
- Length
- 7 amino acids
- Sequence
- LKKTETQ
- Sold as
- TB500 Frag 17-23 10 mg
- Regulatory status
- Not FDA-approved. In July 2026 the Pharmacy Compounding Advisory Committee recommended certain nominated TB-500 bulk forms for 503A-list inclusion; FDA has not issued a final determination. This does not verify or approve a seller’s seven-amino-acid fragment. prohibits TB-500.
- Also known as
- Thymosin β4 actin-binding region
Sources. What this page rests on.
Every source behind this page, with what it says and when it was checked, is in the Source library.
TB-500 Fragment 17-23 in the Source library
Original overview and research notes · annotated 2026-10-01
Historical collection text. Read alongside the claim corrections above; identity or evidence qualifications may supersede this wording.
Recovery (the active piece of TB4)
The seven-amino-acid “active” region of thymosin beta-4.
Positions 17–23 of thymosin beta-4. This stretch is the actin-binding motif, believed to carry much of the full protein’s wound-healing activity. “TB-500” is used loosely for both this fragment and the full protein.
It binds actin, helping cells move toward and close a wound. It may also promote .
Lab and animal wound-healing studies of the fragment and full protein. No human clinical trials of the fragment. It turns up regularly in horse-racing and human doping tests.
Original status record: Not approved. In July 2026 an FDA advisory panel voted to recommend allowing pharmacies to compound it (as TB-500), against FDA staff advice; the FDA has not decided. Banned by WADA.