Research-context information only. Thymosin beta-4 is a research peptide. It is on the FDA 503A bulks Category 2 list. Protocols, doses, and reactions reported below come from published research and self-reported community sources. This article reports what has been documented, not what should be done. Consult a licensed physician for personal medical decisions.
The buying problem is that "TB-500" and "thymosin beta-4" are used interchangeably by vendors despite originally referring to slightly different products. Verifying 4,963 Da on mass spec is the only reliable distinction — full Tβ4 at 43 residues vs truncated synthetic fragments.
This guide covers documented per-mg pricing, COA verification, vial size selection, and red flags. For dosing context, see the TB-500 dosing guide. For the alternative TB-500 buying guide, see TB-500 buying guide.
Tβ4 ships as a lyophilized powder in sealed glass vials. Three factors drive price: vial size, vendor markup, and synthesis quality (full Tβ4 vs truncated fragments).
Current Market Pricing (2026)
Vial Size
Typical Price Range
Price Per mg
Best For
2mg
$15-30
$7.50-15/mg
Tolerance testing only
5mg
$30-60
$6-12/mg
Standard short cycles
10mg
$50-100
$5-10/mg
Standard 250-500mcg/day — best all-around
10mg × 5 (kit)
$220-450
$4.40-9/mg
Extended cycles
The pattern: 10mg vials are the most-cited size for cost efficiency. Per-mg pricing is similar to BPC-157 despite Tβ4 being a longer peptide — vendor competition is high in this category.
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How to Verify Thymosin Beta-4 Quality
Tβ4 is a 43-amino-acid peptide. At 43 residues, solid-phase peptide synthesis yields drop sharply, and truncated byproducts are common synthesis impurities.
What a COA Should Include
Identity Confirmation
Mass spec confirming 4,963 Da for full Tβ4
Sequence verification — 43-residue full sequence
Truncation byproducts (Tβ4 fragments at 2,000-4,000 Da) noted as separate peaks if present
Purity Testing
HPLC purity at 98%+ (challenging at 43 residues — 95-98% is more common)
Single dominant peak; truncation byproducts visible as smaller secondary peaks
10mg · sold research-use-only · we may earn a commission
Choosing the Right Vial Size
The 28-Day Stability Rule
Tβ4 reconstituted with bacteriostatic water and refrigerated is documented stable for roughly 28 days in published peptide-stability data. With sterile water (no preservative), the window collapses to ~24 hours.
Practical implication: A 10mg vial at 500mcg/day loading fits the window. At lower 250mcg/day or 3×/week maintenance, staged reconstitution or smaller 5mg vials are common.
Vial Size by Protocol
Tolerance testing:
A 2mg or 5mg vial is the smallest unit cited
1-3 weeks at standard doses
Standard 500mcg/day loading + 250mcg maintenance protocol:
10mg vial during loading (20 days at 500mcg)
5mg vial during maintenance (with staged reconstitution)
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Frequently Asked Questions
Is thymosin beta-4 legal to buy?
Thymosin beta-4 (Tβ4) is sold as a research peptide labeled 'not for human consumption.' It is not FDA-approved. As of 2024-2026, Tβ4/TB-500 has been added to the FDA 503A bulks Category 2 list, restricting compounding pharmacy production. Purchasing research peptides is legal in most US jurisdictions.
How much does thymosin beta-4 cost per month?
Community subcutaneous protocols use 250-500mcg/day. Monthly mass at 500mcg/day is 15mg. Research-vendor 5mg vials run $30-60 and 10mg vials run $50-100. Monthly cost ranges from $90-300 depending on protocol and vial size.
What's the difference between TB-500 and full thymosin beta-4?
Most research-vendor 'TB-500' is full thymosin beta-4 (Tβ4) — 43 amino acids, 4,963 Da. The original TB-500 trademark referred to a specific synthetic fragment, but in practice the labels are used interchangeably and most vendors ship full Tβ4. Always confirm 4,963 Da on the COA — partial fragments at lower mass are common substitutes.
What vial size should I buy?
5mg and 10mg vials are the most-cited sizes. 10mg fits standard community protocols within the 28-day reconstitution stability window. 5mg vials are common for tolerance testing or shorter cycles.
What purity should I look for in thymosin beta-4?
Third-party HPLC at 98%+ purity, plus mass spec confirming 4,963 Da. Tβ4 is a 43-residue peptide — at the upper end of cost-effective synthesis. Truncated byproducts (Tβ4 fragments at 2,000-4,000 Da) are common synthesis impurities visible on HPLC.
Can I buy thymosin beta-4 from a compounding pharmacy?
Not legally as of 2024-2026. Tβ4 is on the FDA 503A Category 2 bulks list. Research vendors are the documented option for buyers in this category.
This article is for educational and informational purposes only. It is not medical advice and should not be used to diagnose, treat, or prevent any condition. Consult a licensed healthcare provider before using any peptide.
