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Stability testing stores samples of a finished product under controlled heat, humidity and light. The lab then checks them at set intervals to see how long they stay safe, potent and unchanged. Accelerated studies give early results in about 3 to 6 months. Real-time studies run for the full shelf life you want to claim, often 24 months, and confirm the expiry date.
Founders often see stability testing as a box to tick before launch. In practice, it answers a question every retailer and customer will ask. Will this product still work, look and smell right on its expiry date? This guide explains how stability studies work for skincare and supplements, which conditions labs use, and how long studies take.
What stability testing checks
A stability study tracks the properties that matter for your product type. The list differs between a face cream and a capsule. Still, the idea is the same: measure at the start, store under set conditions, then measure again.
| Property | Skincare example | Supplement example |
|---|---|---|
| Potency | Vitamin C or retinol level | Label-claim amount of each active |
| Physical | Colour, odour, texture, separation | Hardness, colour, clumping, capsule brittleness |
| Chemical | pH, viscosity, oxidation | Moisture content, degradation products |
| Microbial | Contamination over time; preservative performance | Microbial limits; viable count for probiotics |
| Packaging | Pump function, reaction with the container | Moisture getting through the bottle or pouch |
A product passes when every property stays within its specification for the whole period. So if vitamin C drops below the claim at month 15, your shelf life is under 15 months.
Accelerated vs real-time stability testing
There are two main kinds of study, and most products use both.
Accelerated studies store samples at higher temperature and humidity to speed up ageing. They give early warning of problems and a first estimate of shelf life in months instead of years. Many formulators use a rough rule: chemical reactions run about twice as fast for every 10°C rise. However, it is only a guide. Real products don’t always follow it, especially emulsions and anything with natural ingredients.
Real-time studies store samples at normal storage conditions and test them until the end of the intended shelf life. They are slower, but they give the result regulators and retailers rely on.
For natural health products in Canada, Health Canada’s GMP guidance is direct about this. Accelerated testing gives preliminary data, but you must use real-time studies to verify any shelf life you extrapolate. You also count the expiry date from the day you first made the batch, not the day you packaged it. See Health Canada’s NHP good manufacturing practices guide for the full wording.
Standard stability testing conditions
Most stability programs borrow the conditions in the international ICH Q1A(R2) guideline. ICH wrote it for pharmaceuticals, but supplement and cosmetic labs widely use it as a reference.
| Study | Storage condition | Minimum period in the guideline |
|---|---|---|
| Long-term (real-time) | 25°C ± 2°C at 60% RH ± 5% (or 30°C/65% RH) | 12 months at submission, continued to full shelf life |
| Intermediate | 30°C ± 2°C at 65% RH ± 5% | 6 months, used if accelerated results show significant change |
| Accelerated | 40°C ± 2°C at 75% RH ± 5% | 6 months |
| Refrigerated products | 5°C ± 3°C long-term, 25°C/60% RH accelerated | 12 months and 6 months |
The guideline also sets a testing rhythm for long-term samples. Labs test every 3 months in year one, every 6 months in year two, then yearly. For accelerated studies, it recommends at least three time points, such as 0, 3 and 6 months. The full text is in the ICH Q1A(R2) guideline.
Health Canada’s NHP guidance is less prescriptive. It doesn’t fix the time points. Instead, it expects a written protocol, enough intervals to spot trends, and a stability report for every product.
Stability testing for skincare: what’s different
Creams, lotions and serums are more fragile than most supplements. Water, oils and emulsifiers can separate, and many actives react with air and light. A skincare stability program usually adds:
- Freeze-thaw cycling. Samples move between cold and room temperature several times to simulate winter shipping. Emulsions that split here would split in a delivery truck.
- Light exposure. Vitamin C, retinol and some botanical extracts darken or weaken in light. That decides whether you can use a clear bottle.
- Packaging compatibility. We store the formula in the actual jar, pump or tube, because some packaging absorbs fragrance or lets in air.
- Preservative efficacy (challenge) testing. This confirms the preservatives still protect the product through daily use.
Welsdom’s custom formulation work covers accelerated and real-time stability, photostability, temperature cycling and packaging compatibility. On a custom skincare project, stability and safety testing comes after the sample rounds. Then we lock the formula for production.
In most cases, Canadian cosmetics don’t need an expiry date. Even so, you need data behind any shelf life or “use within” period you print. Many brands use a period-after-opening symbol, such as “12M”, based on in-use testing.
Stability testing for supplements: what’s different
Capsules, tablets, powders and gummies are generally more stable than emulsions, but they have their own weak points:
- Moisture. Powders clump and gummies sweat or harden when humidity gets in. Container choice and desiccants matter.
- Sensitive actives. Probiotics, some vitamins and omega-3 oils degrade faster than minerals. Formulators often add a small overage to some actives so the label claim still holds at expiry.
- Probiotic counts. If the label shows a viable count, you must show it holds to the end of shelf life.
Our post on testing required for supplement products in Canada covers stability alongside identity, potency and microbial testing. Most supplements carry a shelf life of about 2 years.
How long does stability testing take?
Here is a realistic timeline for a new product, in 4 steps:
- Protocol and first samples: a few weeks, once you finalize the formula and packaging.
- Accelerated results: about 3 months for an early read, 6 months for a full accelerated study.
- Launch decision: many brands launch on solid accelerated data with a conservative expiry date, while real-time testing continues.
- Real-time confirmation: runs for the full shelf life claimed, such as 24 months. If real-time data supports it, you can extend the expiry date later.
The practical lesson is to start early. Stability testing should begin as soon as you settle the formula and packaging, not after the first production run. Changing the packaging or the formula later usually means testing again.
Frequently Asked Questions
What is the difference between accelerated and real-time stability testing?
Accelerated testing stores samples hot and humid, such as 40°C and 75% relative humidity, to predict shelf life quickly. Real-time testing uses normal conditions, such as 25°C and 60% RH, for the full shelf life.
How long does stability testing take for skincare?
An accelerated study usually gives early results in about 3 months and a fuller picture by 6 months. Real-time testing continues for the shelf life you claim, often 12 to 36 months for creams and serums.
Is stability testing required for supplements in Canada?
Yes. Health Canada requires a completed stability study for each natural health product sold in Canada. Also, real-time data must verify any shelf life estimated from accelerated results.
Do I need new stability testing if I change packaging?
Usually, yes. A new bottle, pouch or pump can change how much air, light or moisture reaches the product. Health Canada also advises re-evaluating shelf life after significant formula, process or packaging changes.
Can I launch before real-time stability testing finishes?
Many brands do, using accelerated data and a conservative expiry date, while real-time testing continues. The real-time results then confirm or adjust the date on future batches.
When you’re ready to build stability testing into a new formula from day one, start on our custom formulation page.