What a lot number is
A lot number, also called a batch number, is a code that identifies one batch of a material: a quantity made in one process or series of processes so that it is expected to be uniform within set limits. Every container filled from that batch carries the same lot number, and the manufacturer files the batch records under it, from starting materials and test results to where the containers were sent.
The ICH Q7 manufacturing guideline defines a batch number as a unique combination of numbers, letters or symbols that identifies a batch and from which its production and distribution history can be traced. That is why the lot number, not the product name, is what connects a container to its documents.
Results from one lot do not carry over to the next. Purity, peptide content and water content can differ from batch to batch, so each lot has its own documents.
Lot number vs batch number
In most documents the two terms mean the same thing; ICH Q7 writes “batch (or lot)”. Labels abbreviate them as LOT, Lot No., Batch or B/N. Some companies use batch for one production run and lot for a quantity released or shipped together, which can be part of a batch or a blend of batches. If one document set uses both words, ask which one the certificate of analysis refers to.
A lot number is also easy to confuse with other codes printed nearby. The table shows what each identifies.
| Code | What it identifies | Changes from batch to batch? |
|---|---|---|
| Lot or batch number | One batch of one material. | Yes. Each new batch gets a new number. |
| Catalog number or SKU | A product entry in a supplier’s catalog, such as CU50. | No. The same code covers every batch of that product. |
| Report or COA number | One certificate or test report. | Each document has its own number. |
| Serial number | One individual unit, such as an instrument. | Each unit has its own number. |
| CAS number | A chemical substance, such as 89030-95-5 for GHK-Cu. | No. It belongs to the substance, not to a batch. |
Where the lot number is printed
The same lot number should appear on every record that describes the goods:
- The vial or container label, usually next to a manufacturing date and a retest or expiry date.
- The outer box or pack label.
- The certificate of analysis for that batch.
- A third-party test report, in the field for the submitted sample’s batch.
- The packing list or invoice, when the supplier records lots there.
Manufacturing, retest and expiry dates
Dates printed with a lot number refer to that batch. The manufacturing date is when the batch was made. ICH Q7 describes a retest date as the date when a material should be examined again to confirm that it is still suitable, and an expiry date as the end of the period during which it is expected to stay within its specifications if stored under the stated conditions.
A retest date is therefore not an expiry date: after it, the lot is tested again before further use rather than discarded automatically. Both dates assume the storage conditions on the label or in the lot documents.
Lot numbers on third-party test reports
On a manufacturer’s certificate of analysis, the lot number comes from the manufacturer’s own batch records. On a third-party test report, the batch field is usually copied from what the submitter wrote on the sample form: the laboratory tests the sample it receives and does not trace it back to a production batch. Some reports leave the field empty; in our report library such a field reads “Not printed on the report”.
Each report covers only the sample and batch printed on it. Verify it on the issuer’s website and check that the lot number matches the goods you receive.
Match the lot number from quote to receipt
Ask for the documents for the exact lot in your quote. A report describes only the batch it tested, so check that its lot number matches the lot you receive.
- Ask for the lot number with the quote, together with the documents for that lot.
- On receipt, compare the lot number on each vial and box with the documents and the packing list.
- Record the lot number in your inventory and in the laboratory notebook for each experiment, so that a change in results can be traced to a change of lot.
- Store and label containers from different lots separately.
- If a lot number is missing, unreadable or different between documents, ask the supplier in writing before you use the material.
For laboratory research. Not for human or animal use.