How to Read Peptide Vial Labels: Lot Numbers, Concentrations, and Expiration

The Core Information You'll Find

Peptide name: The compound itself (e.g., "Semaglutide," "BPC-157," "TB-500"). Some labels use abbreviations—know which ones apply to your protocol.

Total quantity: Usually listed as "mg" (milligrams) or "mcg" (micrograms). This is the total amount of peptide powder in the vial. Example: "10 mg Semaglutide."

Vial volume: The total liquid capacity (typically 10 mL). This is the amount of bacteriostatic water (BAC water) you'll add if reconstituting.

Concentration after reconstitution: Some pre-filled vials state this (e.g., "100 mcg/mL"). This tells you how many micrograms are in each milliliter after the vial is prepared.

Lot number: A unique identifier (alphanumeric) assigned by the manufacturer. Example: "LOT# AB12345." This links your vial to a specific production batch and is essential for tracking.

Expiration date: Listed as "EXP" followed by month/year. This indicates shelf life of the sealed, stored vial.

Reconstitution date: Once you've mixed the vial with BAC water, write this date on the label. Most reconstituted peptides remain stable for 30 days refrigerated, though this varies by compound.

Understanding mg vs. mcg (The Critical Distinction)

Milligrams (mg) = 1,000 micrograms (mcg)

A vial containing "10 mg" of semaglutide contains 10,000 mcg. If you reconstitute this 10 mg vial in 10 mL of BAC water, the concentration becomes:

If your dose is 0.5 mg (500 mcg), you'd draw 0.5 mL.

Common error: Confusing the total amount with the dose amount. Your vial might contain 50 mg (enough for many doses), but each injection might be just 1 mg. Always verify which unit (mg or mcg) is used in your dosing instructions.

Lot Number Tracking

The lot number isn't just a random code—it's your safety link. Keep a record:

If you experience unexpected reactions, the lot number allows you and your healthcare provider to check whether other users reported issues with that production batch. This is how contamination or stability problems get identified.

Expiration Date Interpretation

Pre-reconstitution (sealed vial): The printed expiration date assumes proper storage (room temperature, away from light). Unopened vials should be discarded after this date.

Post-reconstitution: Once you add BAC water and open the vial, the reconstituted peptide has a shorter shelf life:

If you're unsure, discard by 30 days to be safe. Using expired peptides risks reduced potency or increased contamination risk.

Reading the Concentration Line

A vial might state: "100 mcg/mL after reconstitution in 10 mL BAC Water"

This means:

If you add more or less BAC water than specified, the concentration changes. Adding only 5 mL would create 200 mcg/mL, doubling the concentration.

Manufacturer and Pharmacy Information

Most vials include:

This information matters if you need to contact the source about questions or issues.

Storage Instructions on the Label

Look for lines like:

Follow these exactly. Storage errors can degrade peptides or promote bacterial growth.

Reconstitution Instructions

Pre-reconstituted vials often include directions like:

Shaking rather than rolling can denature peptides and create bubbles. Always read and follow the manufacturer's reconstitution method.

Red Flags on a Label

Be cautious if:

When in doubt, contact your pharmacy or healthcare provider before using the vial.

Creating a Personal Vial Log

Using tools like MyProtocolStack, create an entry for each vial including:

This creates a complete audit trail and catches dosing errors quickly.

This article is for informational and educational purposes only and does not constitute medical advice. Always consult a licensed healthcare provider before starting, adjusting, or stopping any peptide protocol. MyProtocolStack is a protocol tracking and blood work analysis platform — it is not a medical device and does not provide clinical recommendations.