What We Screen Peptide Companies For Before Purchasing

1. Endotoxin Testing

Purity isn't enough. A peptide can be chemically pure while still containing bacterial endotoxins, which aren't detected by standard purity testing. We look for companies that perform endotoxin testing (typically using the LAL assay), especially for products intended for sterile applications. Given we're working the gut angle with our clients we certainly don't want to add to their endotoxin load.

2. Fillers & Excipients

We want to know exactly what's in the vial besides the peptide.
Questions we ask:

• Does the product contain any fillers?

• If so, which ones? (Usually will be Trehalose or Mannitol)

• Why were they added?

• Are the quantities disclosed?

Given the type of clients we work with, we generally prefer products without unnecessary excipients whenever possible. If someone has weak kidneys under no circumstances should they be using peptides full of filler. And those with MCAS/MCS may need to test their sensitivity.

3. Batch-Specific Third-Party Testing

A COA means very little if it isn't tied to your specific vial.
We look for:

• Independent third-party testing (not in-house)

• HPLC purity testing

• Mass spectrometry confirming identity

• Batch or lot numbers on the COA that exactly match the vial

• Testing that is recent and traceable

4. Traceability

Can the company demonstrate where the product came from and how it moved through the supply chain?

The more transparent the chain of custody, the more confidence we have that the tested product is the one being sold. Traceability is becoming an increasingly important quality marker.

5. Real-World Customer Experience

Lab testing tells you what's in the vial. Customer feedback tells you how consistently the company performs.

We look for:

• Long-term reputation

• Consistent reviews across multiple platforms

• How the company handles problems

• Whether customers continue buying from them over time

One glowing review means very little. Hundreds of consistent experiences are much more meaningful. Having worked with peptides going on 6 years we consistently receive feedback that CanLab and Limitless are noticeably superior when clients try out multiple companies. Likely due to them producing products with the least % filler on the market.

6. Transparency

Companies that are proud of their quality usually make it easy to verify.
We appreciate when companies openly publish:

• Batch-specific COAs

• Testing methodology

• Manufacturing standards

• Endotoxin or sterility testing (if performed)

• Complete ingredient lists

If obtaining basic quality information requires multiple emails or evasive answers, that's a red flag.

7. Consistency Over Marketing

Fancy branding doesn't guarantee quality.

We're generally more interested in:

• Consistent testing

• Honest documentation

• Transparent communication

• Repeatable quality

than marketing claims like "pharmaceutical grade" or "99.9% pure" without supporting evidence.