Thymosin beta-4 side effects and risks

Reported side effects

• Eye-drop pain: ARISE 3: 23/350 active versus 16/349 vehicle had instillation site pain., mild. Persistent pain or reduced vision needs eye assessment. (source)
• Eye-drop irritation: ARISE 3: 5/350 active versus 2/349 vehicle had instillation site irritation., mild (source)
• Reduced visual acuity during eye trials: ARISE 3: 12/350 active versus 7/349 vehicle. This does not establish drug causation., serious. New vision loss needs urgent eye care. (source)
• IV trial laboratory or ECG changes: NL005 repeat dose study: events in 16/24 active versus 5/6 placebo; one ECG related withdrawal in each group., moderate. Research infusions included ECGs and lab monitoring; these are not home-injection safety data. (source)
• Immune reactions from unregulated injections: Long term subcutaneous immune risk is not quantified. Product impurities and identity uncertainty add risk., serious (source)
• Itching after topical skin application: A review describes drug related pruritus in the 250 mcg skin cohort; complete primary safety counts were unavailable., mild (source)

Stop and get help if

• Throat or tongue swelling, breathing trouble, collapse: Stop use and call emergency services now.
• Spreading injection-site redness, heat, pain, pus or fever: Stop injections and get urgent same-day assessment. Confusion, fast breathing or fainting needs emergency care.
• New loss of vision, severe eye pain or a worsening corneal wound: Stop the eye product and get urgent ophthalmic care.
• Chest pain, collapse or persistent new palpitations: Stop use and seek emergency assessment.

Who should avoid it

• pregnant: Precaution: human fetal safety is unknown. Trial pregnancy exclusions do not establish safety.
• breastfeeding: Precaution: infant exposure and effects are unknown.
• tryingToConceive: Precaution: reproductive safety is not established.
• under18: Adult self-use only. Limited pediatric skin-trial eligibility does not establish an injection dose.
• activeCancer: Precaution: Tβ4 affects angiogenesis and cell migration. Whether dosing promotes human cancer is unknown.
• cancerHistory: Discuss prior cancer before exposure; long-term recurrence risk is unknown.
• other: A prior serious reaction to this peptide or an excipient should stop further exposure.
• kidneyDisease: No validated impairment dose adjustment is established for community injections.
• liverDisease: No validated impairment dose adjustment is established for community injections.
• heartCondition: Investigational cardiac use required hospital care. ECG changes occurred in healthy-volunteer trials.
• diabeticRetinopathy: Eye disease needs specialist review. Corneal trial results do not establish retinal safety of injections.
• surgeryPlanned: Tell the surgical team. Pain improvement does not prove structural healing or readiness for activity.
• immunosuppressed: Unregulated injections increase infection concerns; approved eye or wound care should not be delayed.
• bleedingDisorder: Injection-related bleeding is a concern, particularly intramuscularly.
• testedAthlete: WADA 2026 prohibits Tβ4 and derivatives at all times.

Interactions

• TB-500 and duplicate Tβ4 products: Products may duplicate exposure or contain different molecules despite similar names.
• Anticoagulants: Injection-related bruising or bleeding, especially with intramuscular injections. No specific Tβ4 interaction was established.
• BPC-157 and other repair peptides: No controlled human trial establishes a routine recovery stack. A tiny knee series cannot show added Tβ4 benefit.
• ACE inhibitors: ACE breaks down Ac-SDKP, a Tβ4 fragment; ACE inhibitors raise endogenous Ac-SDKP. Clinical effects with added Tβ4 are unknown.

Product quality risks

• In a 2018 study, all three sampled TB-labelled products contained full-length Tβ4; two claimed TB-500 fragment.
• Mass spectrometry detected Tβ4-related modifications despite no quantifiable impurity peaks by UV in those samples.
• The wider 27-product study found dose variation and some toxic-metal contamination. Its 5–75% purity range concerned cysteine-containing peptides, not Tβ4.
• Unauthorized injections have no assurance of sterile contents, correct dose or reliable expiry.