What GDF-8 is
GDF-8 is growth differentiation factor 8, better known as myostatin: the protein made by muscle that stops muscle growing. Animals and one child born without working myostatin have roughly twice the normal muscle mass, which is why drugs that block it have been tested in muscular dystrophy, sarcopenia, inclusion body myositis and obesity. What research stores sell as GDF-8 is either the myostatin protein itself, which would if anything reduce muscle, or a propeptide, antibody or follistatin product meant to block it. No myostatin inhibitor is an approved medicine and all of them are prohibited in sport. Read the full GDF-8 guide, with the published research and references.
Before you choose a GDF-8 supplier
Price per mg is only half the comparison. Check that the supplier publishes a certificate of analysis for the batch it is selling, ideally from an independent laboratory, and that the certificate confirms identity as well as purity: our guide on how to read a COA shows what to look for. A price far below the rest of the list is more often a warning than a bargain; peptide prices explained sets out why.
For what GDF-8 is and what published studies have found, see our GDF-8 guide. Handling questions are covered in how to store peptides, and the peptide calculator converts a vial size and water volume into concentration and syringe units. Rules on buying and importing differ by country: read are peptides legal in the US? and see all suppliers serving the US.
Checking a GDF-8 certificate of analysis
- The certificate names a laboratory you can find independently, and ideally one with no stake in the result.
- It carries a batch or lot number that matches the product page or the vial label, and a test date.
- It confirms identity by mass spectrometry, not only purity by HPLC. Purity alone does not show the vial contains GDF-8.
- It includes the chromatogram and mass spectrum, not just a summary table.
- Where the laboratory offers online verification of its reports, the report number checks out.
Red flags
- No certificates at all, or certificates available only “on request”.
- The same certificate used for several products or several years of stock.
- Payment only by cryptocurrency or bank transfer, with a discount for paying that way.
- A price far below every other supplier on this page.
- No company name, address or way to contact the business other than a web form.
- Vials labelled only with a code rather than the product name and strength.
How to spot a fake peptide supplier explains each of these in more detail, and third-party peptide testing covers what independent results can and cannot prove.
Vials, capsules and pre-mixed products
Most research peptides are sold as freeze-dried (lyophilised) powder in sealed vials, which is mixed with a diluent such as bacteriostatic water before use in the lab. Some suppliers also sell pre-mixed solutions, nasal sprays or capsules under the same name. These are different products with different stability and dosing, so compare price per mg only between the same form, and check which form a listing is before comparing it with the rest of the table.
How this list is built: suppliers appear because they list GDF-8 on their own website, read by our catalogue checks; nobody pays to be included or to move up. Ranking is by PepFinder Score. Prices, sizes and stock are as each site listed them when checked and may have changed. Provisional scores are based on incomplete research.
