The shelf life printed on a pack is a promise: until this date, the product will still meet its specification when stored as the label says. A stability study is how that promise is earned. For herbal and nutraceutical products it is also where many quality problems first show up: capsules that harden, powders that cake, syrups that ferment, markers that drift.
This guide explains what a sound stability programme covers and what to ask your manufacturer. It is general guidance for B2B buyers, not regulatory advice.
Why it matters even when the law is light
For US dietary supplements, FDA does not require an expiration date. Its Small Entity Compliance Guide is clear, though, that you should have data to support any expiration, shelf or "best if used by" date you place on the label. Many other markets expect stability evidence in a product file, and retailers and importers increasingly ask for it.
Medicinal-product rules are stricter. In Europe, specifications for herbal medicinal products apply "at release and during the shelf-life" (EMA guideline on specifications). Even where your product is a food supplement, that is a sensible standard to adopt.
The reference designs
Most supplement and herbal manufacturers borrow from pharmaceutical guidance:
- ICH Q1A(R2), the international guideline on stability testing of new drug substances and products, available from FDA (Q1A(R2)) and in ICH's quality guidelines.
- WHO's stability testing guideline (TRS 1010, Annex 10), which sets long-term storage conditions by climatic zone, including 30 °C / 75% relative humidity for hot and very humid regions.
These documents are written for medicines. Applying their structure to a supplement is good practice, not a legal requirement in most food-supplement markets.
What a sound study specifies
1. Storage conditions that match where the product will live
Long-term conditions should reflect the climate in which the product will be stored and sold. A product for hot, humid markets should be tested under conditions that represent them. Accelerated conditions (higher temperature and humidity) are used to reveal likely changes sooner and to support a provisional shelf life, but real-time data at long-term conditions is what ultimately confirms it.
2. The final pack
Stability belongs to the product in its pack. A capsule in an HDPE bottle with desiccant and the same capsule in a blister can behave very differently. Test in the commercial container and closure. If you change pack later, ask whether new data is needed.
3. Batches
Pharmaceutical guidance generally expects data on more than one batch. For supplements, buyers should at least ask whether the study used production-representative batches made with the commercial process and suppliers.
4. Time points
A typical programme tests at the start and at regular intervals across the proposed shelf life and beyond, with more frequent points in the first year. Agree the schedule in advance.
5. Parameters
Choose tests that would detect the changes most likely to matter for your product:
| Dosage form | Typical stability parameters |
|---|---|
| Capsules | Appearance, moisture, disintegration, assay or markers, microbiology |
| Tablets | Appearance, hardness, friability, disintegration, moisture, assay or markers, microbiology |
| Powders | Appearance, flow and caking, moisture, assay or markers, microbiology |
| Syrups and liquids | Appearance, pH, sediment, preservative content where relevant, assay or markers, microbiology |
For botanical products, a chromatographic fingerprint at start and end can show whether the overall profile has shifted, not only the single marker you assay.
6. Acceptance criteria
Stability results are judged against the same specification used at release, or a justified shelf-life specification. Agree in writing what counts as a failure.
Questions to ask your manufacturer
- Which conditions, and why do they fit my markets?
- Is the proposed shelf life based on real-time data, accelerated data, or both?
- Which batches, in which pack?
- Which parameters and methods, and what are the limits?
- What happens if a time point fails?
- Will the study be repeated if the formula, an ingredient supplier or the pack changes?
Red flags
- A shelf life with no study behind it, or one copied from a "similar" product.
- Accelerated data alone used to claim a long shelf life, with no real-time study running.
- Tests that cannot detect the likely failure (for example no moisture test on a hygroscopic extract).
- A study run in a different pack from the one you will sell.
How we approach this at Amulya Labs
Every Amulya Labs order is supplied with COAs and the supporting documentation buyers need, from a WHO-GMP certified facility, and our formulations are designed on a scientific basis from the start. If your markets or pack call for a specific stability programme, put it in your brief and we will discuss how best to support it before the first batch.
This guide is general information, not legal or regulatory advice.