TB-500
Thymosin Beta-4 (synthetic fragment)
Also known as: Tβ4, Thymosin Beta-4, RGN-352
Last updated May 4, 2026
What is TB-500?
If you’ve tried BPC-157 and it helped but didn’t finish the job, or you’re dealing with multiple injury sites and lingering inflammation, TB-500 is the compound you keep seeing mentioned alongside it.
TB-500 is a synthetic version of Thymosin Beta-4, a naturally occurring 43-amino-acid protein found in virtually every cell in your body except red blood cells. It’s present in high concentrations in platelets, white blood cells and wound fluid. It works by binding to actin (a structural protein critical for cell movement), helping cells migrate to injury sites, promoting new blood vessel formation, reducing inflammation and decreasing scar tissue. If you’ve read our BPC-157 profile, think of TB-500 as its complement — BPC-157 works through growth factor signaling and nitric oxide pathways; TB-500 works through actin regulation and stem cell mobilization. Different angles on tissue repair.
What Does the Research Actually Show?
Foundational study (Malinda et al., 1999) showed 42% faster re-epithelialization at 4 days and 61% at 7 days in rats, with increased collagen and angiogenesis. Confirmed across healthy, diabetic and aged animal models.
Most clinically advanced application. RegeneRx’s RGN-259 completed multiple clinical trials for dry eye syndrome and corneal wound healing. Phase 2 trials showed significant improvement. Strongest human trial data for any TB-500 application.
Animal studies show accelerated muscle fiber regeneration, increased satellite cell proliferation, reduced scarring. Strong practitioner consensus but human RCTs are the missing piece.
It’s worth noting: while TB-500 has human clinical trial data for ophthalmic applications (corneal repair), the musculoskeletal and tissue repair benefits that most consumers seek have not been tested in controlled human trials. The animal data is consistent and the practitioner consensus is strong, but animal data and practitioner consensus are not proof.
How Is TB-500 Administered?
| Route | Subcutaneous injection |
| Dosage range | 2.0–2.5 mg per dose |
| Frequency | Twice weekly during loading, less frequent during maintenance |
| Protocol | Loading and maintenance phases vary between providers; specific course lengths not established in controlled human trials |
| Access | Provider-prescribed via compounding pharmacies; no FDA-approved formulation for any human indication |
For injection supplies and self-administration basics, see our Injectable Peptide Supplies Guide →
What Are the Side Effects and Risks?
- Injection site reactions — mild and the most commonly reported side effect.
- Headache and lightheadedness — transient.
- Angiogenesis concern — TB-500 promotes new blood vessel formation, which theoretically could support tumor growth in someone with active cancer. No studies show TB-500 causes cancer, but people with active malignancies should avoid it.
- Contraindications: active cancer, pregnancy, breastfeeding.
- Banned by WADA. A positive test can end a season or career.
Who Should NOT Use TB-500?
If you have an active malignancy or recent cancer history: TB-500 promotes angiogenesis (new blood vessel formation). Theoretically, this could support tumor vascularization. No studies have shown that TB-500 causes cancer, but people with active cancers should avoid this compound. Like BPC-157, this conversation belongs with your oncologist, not your peptide provider.
If you are pregnant or breastfeeding: No safety data exists. Absolute contraindication.
If you are a competitive athlete in a tested league: TB-500 is prohibited by WADA and major equine racing authorities. Provider prescription is not a defense under anti-doping rules.
Before You Start: Get Baseline Labs
We recommend baseline lab work before starting any peptide protocol so you and your provider can track changes. Key markers include CBC, CMP, CRP (C-reactive protein) and inflammatory markers (ESR, ferritin).
Ask your provider about ordering these labs, or search for direct-to-consumer lab testing services in your area.
Order at-home labs from Everlywell →Lab recommendations are the same regardless of which service you use.
What You'll Need
If your provider prescribes an injectable protocol, you'll need basic supplies.
- Bacteriostatic Water (30ml)Link coming soon
- Insulin Syringes 29 gauge (100ct)Link coming soon
- Alcohol Prep Pads (200ct)Link coming soon
- Sharps ContainerLink coming soon
Supply links are affiliate links. We may earn a commission at no cost to you. We only link to commodity supplies, never to peptide products.
- 1For my specific injury, would you recommend TB-500 alone or combined with BPC-157? What’s the rationale?
- 2What loading and maintenance schedule do you recommend?
- 3Given TB-500’s angiogenic properties, is there anything in my health history that makes it inappropriate?
- 4Which compounding pharmacy sources your TB-500, and can they compound it legally right now?
- 5How will we measure progress and what timeline should I expect?
- 6What’s the total cost for a typical loading plus maintenance cycle?
Is TB-500 Legal in 2026?
Not FDA-approved. Removed from Category 2 effective April 22, 2026. PCAC review scheduled for July 23, 2026 — TB-500 is on the agenda alongside BPC-157, KPV, and MOTS-C, with the FDA reviewing it for wound healing. Compounding cannot resume until after PCAC review and a final FDA determination adds TB-500 to the 503A bulks list. The FDA accepts public comments through Docket FDA-2025-N-6895; comments received by July 9, 2026 will be provided to the committee.
How Do I Get TB-500 Through a Legitimate Provider?
No verified providers currently meet our evaluation criteria for this compound. Subscribe to be notified when that changes.
When provider links go live, we’ll disclose all affiliate relationships here.