How to Read a Certificate of Analysis for Your Compounded GLP-1 Medication

A Certificate of Analysis (COA) is the single most important document for verifying the quality of compounded GLP-1 medication. It tells you whether the semaglutide or tirzepatide in your vial is the right strength, free of contamination, and properly manufactured. Yet most patients have never seen one, let alone know how to read one.

This guide walks you through exactly what to look for — and what red flags should make you switch pharmacies immediately.

What Is a Certificate of Analysis?

A COA is a document issued by a laboratory (ideally an independent, third-party lab) that reports the results of testing performed on a specific batch of compounded medication. It's essentially a report card for your medication, verifying that what's on the label matches what's actually in the vial.

For compounded GLP-1 medications, a COA should test for at least three things: potency (is the dose accurate?), sterility (is it free of microorganisms?), and endotoxins (are bacterial toxins absent?).

The 7 Things to Check on a COA

1. Potency / Assay Result

What to look for: The measured concentration of semaglutide or tirzepatide compared to the labeled concentration. Acceptable range: 90-110% of label claim (USP standards). Ideal: 95-105%.

Red flag: Potency below 90% means you're underdosed — your medication won't work as expected. Above 110% means you're getting more than prescribed, increasing side effect risk. The FDA has documented compounded GLP-1 products testing as low as 42% potency.

2. Sterility Testing

What to look for: The COA should show sterility testing results with a clear "Pass" or "No growth detected" notation. The test should follow USP <71> methodology.

Red flag: If sterility testing is absent from the COA, or if results say "not tested" or reference an incomplete testing method, do not use the product. Injectable medications must be sterile — there is no acceptable shortcut.

3. Endotoxin Testing (BET/LAL)

What to look for: Bacterial endotoxin test results showing levels below the USP limit (typically <5 EU/mL for injectable products). The test should follow USP <85>.

Red flag: Missing endotoxin testing. Endotoxins are fragments of bacterial cell walls that can cause fever, inflammation, and in severe cases, septic shock when injected. Endotoxin testing is a minimum requirement for any injectable product.

4. Testing Laboratory Identification

What to look for: The COA should clearly identify which laboratory performed the testing. Ideally, this is a third-party, independent lab (not the pharmacy's own in-house lab). The lab should be ISO 17025 accredited or DEA-registered.

Red flag: No lab identified, or testing performed only in-house. Third-party testing provides an independent verification that the pharmacy can't manipulate.

5. Batch/Lot Number

What to look for: A specific lot number that matches the lot number on your vial. The COA should test the exact batch you received, not a "representative" batch from months ago.

Red flag: Lot number on COA doesn't match your vial, or the pharmacy provides a "general" COA not tied to a specific batch.

6. Date of Testing

What to look for: Testing should be recent — within 30-60 days of the batch's compounding date. For compounded GLP-1 injections, beyond-use dating (expiration) is typically 30-90 days depending on the pharmacy's stability data.

Red flag: Testing date is many months old, or the COA predates your batch by a significant margin.

7. pH and Appearance

What to look for: pH should be within the specified range for the formulation (typically 7.0-8.0 for semaglutide injections). Appearance should note "clear, colorless solution" or similar.

Red flag: pH outside the specified range can affect stability and bioavailability. Any cloudiness, particulates, or discoloration is a safety concern.

Sample COA Checklist

COA Element	Acceptable	Red Flag
Potency	90-110% (ideal: 95-105%)	Below 90% or above 110%
Sterility	Pass / No growth (USP <71>)	Not tested or incomplete
Endotoxins	<5 EU/mL (USP <85>)	Not tested
Lab	Third-party, accredited	In-house only or unidentified
Lot match	COA lot = vial lot	Mismatched or generic
Test date	Within 30-60 days	Months old
pH	Within spec range	Out of range

How to Request a COA

Step 1: Find the lot number on your vial (usually printed on the label or on the packaging).

Step 2: Contact your pharmacy's customer service or your telehealth provider's support team.

Step 3: Request the COA for your specific lot number. Specify that you want third-party testing results, not just an in-house analysis.

Step 4: Review the COA against the checklist above. If anything is missing or concerning, ask follow-up questions.

A pharmacy that responds promptly and transparently to COA requests is one that takes quality seriously. A pharmacy that deflects, delays, or refuses is telling you everything you need to know about their standards.

503A vs 503B: Different COA Standards

503B outsourcing facilities are FDA-registered and must follow current Good Manufacturing Practices (cGMP), including batch testing requirements. Their COAs tend to be more comprehensive and standardized.

503A traditional pharmacies operate under state pharmacy board oversight and are not required to follow cGMP. COA practices vary significantly between 503A pharmacies — some voluntarily test every batch through third-party labs, while others may test infrequently or only in-house.

When evaluating a compounding pharmacy, the COA is one of the clearest indicators of quality. A pharmacy that provides detailed, timely, third-party-verified COAs for every batch is demonstrating a level of quality assurance that protects you as a patient.