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What are the side effects of TB-500?
See what research and FDA's 2026 review report on TB-500 side effects, product quality, warning signs, and when to call a clinician.
Quick answer
TB-500's side-effect profile in people is still being defined. It is not FDA-approved and has no established labeled route. FDA's 2026 review identified no human studies, so most research comes from laboratory and animal work. FDA's 2026 review found no TB-500 adverse-event reports through March 26, 2025, and no published human case reports. The agency's stated concerns are possible immune reactions and impurities. The World Anti-Doping Agency prohibits TB-500 at all times.
- Published
- November 4, 2026
- Last updated
- November 4, 2026
How TB-500 safety has been studied
TB-500 side effects in people are still being defined. FDA's 2026 review identified no clinical studies or human exposure data. It concluded that potential safety risks in humans are unknown1. Most research is laboratory and animal work, much of it on thymosin beta-4 (Tβ4), the protein TB-500 is derived from. Reviewers describe TB-500 as a distinct fragment of Tβ42.
TB-500 began as a veterinary preparation3, and horse-racing labs built tests to detect it. Its record in people comes mainly from reports.
What TB-500 side effects have been reported?
No TB-500 side effects appear in the adverse-event reports or published human cases1 FDA reviewed in 2026. Three record sources held no safety finding:
- Adverse-event reports: FDA's Adverse Event Reporting System (FAERS) held no TB-500 reports through March 26, 20251.
- Case reports: FDA's literature search found no published human cases of TB-500 use.
- Food and supplement complaints: FDA's complaint database held two cases on blended TB-500 and BPC-157 products, neither with a safety assessment.
FAERS reporting is voluntary and incomplete1, so FDA cannot draw definitive safety conclusions from it. Studies add further detail.
What do studies show about TB-500 safety?
FDA's review found no standard animal toxicity studies of TB-500. These include repeat-dose, genotoxicity (DNA damage), and carcinogenicity studies1.
The nearest human safety data come from Tβ4, one of the thymosin peptides. In a placebo-controlled trial, 40 healthy adults received intravenous Tβ4 or placebo4 once, then daily for 14 days. Adverse events were infrequent and mild or moderate, with no serious adverse events. Those results come from the full-length molecule given into a vein.
Mouse research on Tβ4 and tumors points in two directions. Tumor cells engineered to make more Tβ45 grew and spread more. Administered Tβ4 slowed lung tumor growth6 in a second mouse model. The cancer concern for TB-500 is theoretical and a reason for individual review. Product quality is another part of TB-500 safety.
TB-500 product quality and safety
FDA found no public quality tests1 for TB-500 impurities, aggregates, microbial quality, or bacterial endotoxin.
- Identity: Products sold online as TB-500 have not always matched their labels7.
- Immune reactions: FDA notes that injected TB-500 may pose a risk of immune reactions8, heightened by clumping and impurities.
- Sterility: TB-500 products raise sterility and manufacturing consistency2 concerns.
- Storage: TB-500 stability depends on manufacturing, with the free base reported stable below -4°F (-20°C)1 and the acetate below 5°F (-15°C).
Knowing the warning signs after an injection rounds out the safety picture.
How can TB-500 side effects be managed?
The prescribing clinician reviews any new TB-500 side effects. Signs of a severe allergic reaction are an emergency that needs a 911 call9.
- Before starting: Clinicians are encouraged to ask about peptide use2, so share the TB-500 form and source.
- Injection-site reactions: Spreading redness, warmth, tenderness, or pus after TB-500 can signal cellulitis, a bacterial skin infection10.
- Contacting the clinician: Fever with chills or red streaks that spread10 from a TB-500 injection site need prompt clinician review.
- Calling 911: Trouble breathing; swelling of the face, eyes, or tongue; hives; chest tightness; or a racing heartbeat after TB-500 can signal anaphylaxis, which often develops within seconds or minutes9.
Some health histories call for a closer review before starting.
Who should talk to a clinician first?
A clinician reviews health history before TB-500 starts. Some histories deserve extra attention:
| Before using TB-500, discuss | Why it matters |
| Cancer or unexplained growths | Tβ4, the protein TB-500 comes from, has been studied in mouse tumor models5, so a cancer history deserves an individual risk review. |
| Pregnancy or breastfeeding | FDA found no developmental or reproductive studies1 of TB-500. |
| Allergies or past reactions to injected medicines | FDA notes injected peptides like TB-500 may trigger immune reactions8. |
| Other medicines, supplements, or peptides | FDA found no human pharmacokinetic studies1 of how the body absorbs and clears TB-500, so the clinician reviews each combination. |
For athletes, TB-500 also carries limits in competitive sport.
TB-500 is prohibited in sport at all times11 by the World Anti-Doping Agency (WADA). Athletes subject to drug testing can face sanctions and should check current WADA and league rules.
Getting TB-500 in 2026
Superpower will offer TB-500 formulated in FDA-registered facilities in the US, backed by third-party lab testing, and distributed from US-licensed pharmacies. A licensed clinician will review each person's health history to decide whether TB-500 fits their health care. The Superpower peptide waitlist is open now.
TB-500 is not an FDA-approved drug. Under an interim policy announced in October 2026, the Department of Health and Human Services does not intend to take enforcement action12 against state-licensed pharmacies that compound TB-500 and certain other peptides while the 503A Bulks List, the list of ingredients pharmacies may use in compounding, is finalized. The policy applies to six peptides, TB-500 among them13, with conditions that include ingredients from FDA-registered facilities and a patient-specific prescription. Its announcement came after a July 2026 FDA advisory committee recommendation to add TB-500 to the list14, with rulemaking still in progress.