BPC-157 and TB-500 are the two most-stacked research peptides for tissue and tendon support. They work via different mechanisms and have very different molecular weights, which matters for both dosing and for what a real Certificate of Analysis should look like.
BPC-157
TB-500 (Thymosin Beta-4)
Origin
Synthetic fragment of human gastric juice protein
Synthetic fragment of Thymosin Beta-4
Amino acid length
15 aa
17 aa (TB-500 fragment)
Molecular weight
~1419 Da
~1888 Da
Half-life
~4 hours (subcut)
2-3 days (long-acting)
Typical research dose
250-500 mcg/day
2-2.5 mg twice/week
Common stack
Often stacked with TB-500
Often stacked with BPC-157
Primary research focus
GI lining, tendon, ligament
Soft tissue, cardiac, systemic recovery
Identity test (LC-MS) expected mass
~1419 Da
~1888 Da
HPLC purity benchmark
≥ 98%
≥ 97%
Common adulterant risk
Under-fill (less than label)
Mislabel as full TB-4 (TB-500 is a fragment)
Verdict
BPC-157 and TB-500 are complements, not substitutes. They are frequently stacked because BPC-157 is short-acting and localised while TB-500 is long-acting and systemic. When testing either, confirm the exact mass on the LC-MS report - TB-500 vendors sometimes ship full-length Thymosin Beta-4 by mistake, which is a different molecule (~4963 Da).
Frequently asked questions
Can I run both at once?
They have different mechanisms and half-lives so the literature describes them as compatible. Always confirm purity for each vial independently - a stack is only as clean as its dirtiest component.
Why does my TB-500 CoA show a different mass?
TB-500 is a 17-amino-acid fragment of Thymosin Beta-4, not the full 43-aa parent peptide. If the LC-MS reports ~4963 Da you have full TB-4, not TB-500.
Which one should I test first?
Test whichever vial you bought most recently, or whichever vendor you have least experience with. Both samples are A$549 each - LabDoc charges one flat rate per vial, with no volume discount.