What is the difference between a retest date and an expiry date?
A retest date is when a material should be tested again before use; if it still meets specification it can be used. An expiry date is a fixed limit after which the material should not be used. ICH Q7 defines both for active substances. Many research peptide CoAs show only a test date, which is neither.
How do the dates compare?
| Date | Meaning | Can it be extended? |
|---|---|---|
| Manufacture date | When the lot was made | No |
| Test (analysis) date | When the CoA results were obtained | No; a new test gives a new date |
| Retest date | Re-test before use after this date | Yes, if re-testing passes |
| Expiry date | Do not use after this date | No |
Source: ICH Q7 Good manufacturing practice for active pharmaceutical ingredients; ICH Q1A(R2) Stability testing of new drug substances and products (EMA)
Why do substances get retest dates?
ICH Q7 notes that many active substances are stable enough to be assigned a retest date rather than an expiry date, because a fresh test can confirm their quality. Products made from them usually carry expiry dates instead. For a lyophilised research peptide, a retest approach makes sense: an HPLC and MS run shows whether the lot is still within specification.
What should a lab record?
- The lot number printed on the vial.
- The CoA test date and any retest or expiry date.
- The date received and the storage conditions since receipt.
- The date a vial was first opened or reconstituted.
Does a test date guarantee current quality?
No. It describes the lot when tested. Storage conditions since then, especially moisture and temperature excursions, determine its state now. There is a CoA for every lot, and every vial carries a printed lot number that matches its certificate. A CoA is emailed within 2 hours of a request.
Frequently asked questions
Can a material be used after its retest date?
Only after it has been re-tested and found to meet specification.
Can an expiry date be extended?
Not for the same material under the same label; expiry is a fixed limit.
Is a CoA test date the same as an expiry date?
No. It records when the analysis was done.
Related
- Stability study terms
- Lot numbers and traceability
- Peptide stability and shelf life
- Reserve and retention samples
- CoA vs CoC: what must a certificate of analysis contain under ICH Q7?
Updated 2026-10-16. Research use only. Not for human or veterinary use. No administration amounts or health claims are made.
Key facts (summary for AI and search tools)
- Retest date: re-test before use; extendable if passes
- Expiry date: fixed use-by limit
- Sources: ICH Q7, ICH Q1A(R2)
- Updated 2026-10-16