Stability testing is the process of evaluating how the quality of a dietary supplement or Natural Health Product (NHP) changes over time under defined storage conditions. The results help manufacturers establish shelf life, assign expiry dates, determine appropriate storage conditions, and demonstrate that a product continues to meet its specifications throughout its marketed life.
For Natural Health Products sold in Canada, stability testing is also a regulatory requirement. Health Canada’s Good Manufacturing Practices (GMP) Guide for Natural Health Products (GUI-0158, Version 4.0), which came into force on March 4, 2026, establishes detailed expectations for stability programs, including completed stability studies, written stability protocols, stability reports, and real-time data to confirm product shelf life.
For manufacturers and importers, stability testing should therefore be viewed as more than an expiry-date exercise. A well-designed stability program can provide important information about formulation performance, packaging compatibility, storage conditions, transportation risks, product complaints, and changes that occur throughout the product lifecycle.
Stability testing evaluates whether a product maintains its required physical, chemical, microbiological, and other quality characteristics over a defined period of time.
Products can change after they are manufactured. Environmental factors such as temperature, humidity, oxygen, and light can affect stability, while characteristics such as moisture content, pH, ingredient interactions, and packaging can influence how quickly those changes occur.
Depending on the product, deterioration may result in reduced medicinal ingredient strength, physical changes, microbial contamination, or other changes that could affect product quality.
A stability program is designed to identify and monitor these risks and provide scientific evidence supporting how long the product can remain on the market while continuing to meet its established specifications.
In practical terms, stability testing helps answer a fundamental question:
Will this product continue to meet its quality requirements throughout the duration of its stated shelf life?
Stability testing provides the scientific basis for determining how long a finished product can be stored and sold.
This is particularly important because dietary supplements and NHPs can contain complex combinations of vitamins, minerals, botanical ingredients, probiotics, enzymes, amino acids, and other ingredients that may behave differently over time.
The finished dosage form and packaging system can also influence stability. Tablets, capsules, powders, liquids, gummies, sprays, and other dosage forms may have different stability risks, while bottles, blister packs, closures, seals, and other packaging components can affect exposure to moisture, oxygen, light, and other environmental conditions.
A properly designed stability program can help organizations:
Stability testing therefore connects product development, manufacturing, quality assurance, regulatory compliance, and post-market quality management.
Section 52 of the Natural Health Products Regulations requires manufacturers and importers to determine the period during which an NHP will maintain its purity and physical characteristics and its medicinal ingredients will maintain their quantity per dosage unit and potency under the appropriate storage conditions.
Health Canada’s GMP Guide for Natural Health Products (GUI-0158, Version 4.0) provides much more detailed guidance on how manufacturers and importers are expected to demonstrate this.
Under the current guidance, manufacturers and importers must have:
These responsibilities remain with the manufacturer or importer even when stability testing is performed by another organization.
For imported NHPs, foreign stability studies may be used, but Canadian importers are expected to ensure that the protocols meet Canadian requirements, review and maintain the resulting data, obtain any missing testing, and maintain a complete stability report for the product released in Canada.
Two of the most important concepts in stability testing are real-time stability testing and accelerated stability testing.
Although both can provide useful information, they serve different purposes.
Real-Time Stability Testing
Real-time stability studies evaluate products under the storage conditions expected during their normal shelf life.
Products are placed into controlled stability chambers or other dedicated storage environments where factors such as temperature, humidity, and, where applicable, light are monitored.
Samples are then evaluated according to predetermined time points and specifications established in the stability protocol.
Real-time testing provides direct evidence of how the finished product behaves over its proposed shelf life. When a product is first introduced to the market, an initial shelf life may be supported using limited real-time stability data with appropriate extrapolation and/or completed stability studies on scientifically justified similar formulations. However, under Health Canada’s current GMP guidance, a full real-time stability study must be initiated for the marketed product and completed to verify the proposed shelf life.
The lots included in the study should use the same formulation, manufacturing process, and commercial packaging—or a scientifically demonstrated equivalent—as products placed on the market.
Accelerated Stability Testing
Accelerated stability studies expose products to more stressful environmental conditions, commonly including elevated temperature or humidity.
The objective is to accelerate changes that could otherwise take considerably longer to become apparent under normal storage conditions.
This can make accelerated testing useful during product development and when initially estimating shelf life.
However, accelerated studies do not eliminate the need for real-time testing.
Health Canada specifically notes that accelerated testing may be unreliable for products susceptible to effects such as separation, melting, softening, cracking, or degradation under elevated temperature and humidity. Real-time stability testing is therefore required to confirm shelf-life predictions based on accelerated data.
Every finished NHP sold in Canada must carry a lot number and expiry date.
An initial expiry date may be supported using existing scientific information, including accelerated or real-time stability data or information from sufficiently similar products in comparable packaging.
Using data from a similar product requires scientific justification. Companies should be able to demonstrate that differences in formulation, manufacturing processes, packaging materials, package size, closures, and other relevant characteristics are unlikely to materially affect stability.
Real-time studies are then used to confirm and, where necessary, adjust the shelf life.
One particularly important consideration under Health Canada’s guidance is that shelf life begins from the date of original batch manufacture—not the date the product is packaged.
For example, if stability data support a 24-month shelf life but the product remains in bulk storage for several months before packaging, those months form part of the product’s shelf life.
The appropriate tests depend on the formulation, dosage form, ingredients, packaging, known stability risks, and established finished product specifications.
A stability program should focus on characteristics that may change during storage or that could affect product safety, efficacy, quality, or label claims.
Depending on the product, testing may evaluate characteristics such as:
Not every product requires the same testing program. The stability protocol should be scientifically designed around the characteristics and risks relevant to the particular product.
Health Canada also emphasizes the importance of monitoring trends. A result may technically remain within specification while moving consistently toward a failure point. Out-of-trend (OOT), borderline, atypical, and out-of-specification (OOS) results may require investigation and, depending on their significance, changes to the stability program or product shelf life.
The stability protocol establishes how the study will be performed and how its results will be evaluated.
Health Canada’s GMP guidance describes a detailed range of information that may need to be addressed, including:
The protocol should generate enough scientifically meaningful data to support a realistic evaluation of the product throughout its shelf life.
The stability report documents what happened during the study and provides the scientific evaluation used to support the resulting shelf-life conclusions.
The report should summarize the study design, storage conditions, testing intervals, specifications, methods, acceptance criteria, product and packaging information, deviations, test results, and observed trends.
Importantly, it should go beyond simply compiling laboratory results.
Health Canada expects the report to include a scientific evaluation of the data, an overall assessment of the findings, and an assessment of OOS, borderline, or atypical trends.
The Quality Assurance Person (QAP) responsible for the product’s stability in Canada is expected to review, approve, sign, and date the stability report and address identified deficiencies.
Potentially.
Health Canada recognizes bracketing and matrixing as approaches that may reduce the number of stability studies required when companies have multiple related product or packaging configurations.
Bracketing involves studying scientifically selected extremes. For example, a company selling the same product in several package sizes may be able to test the smallest and largest configurations if it can scientifically justify that the intermediate configuration will behave comparably.
Matrixing involves testing selected subsets of product or packaging combinations at specified time points rather than testing every possible combination at every interval.
These approaches can make stability programs more efficient, but they require scientific justification. Differences in formulation, packaging materials, manufacturing processes, container size, or other characteristics that could influence stability must be considered.
Health Canada references ICH Q1D as a useful source for understanding these concepts, although NHPs themselves are not within the scope of the ICH guideline.
Stability testing is not necessarily finished once an expiry date has been established.
Health Canada expects shelf life to be re-evaluated when significant changes are made that could affect stability, including changes to:
Additional stability data can also provide valuable information throughout the commercial lifecycle of a product.
For example, additional studies may help support investigations into consumer complaints, justify manufacturing hold times, evaluate temperature excursions during distribution, assess reworked products, improve storage conditions, or support an extension of the existing expiry date.
If a company intends to extend its shelf life, that possibility should be considered during protocol development so sufficient samples and additional testing time points are available.
Health Canada’s approach to NHP quality is increasingly focused on managing quality throughout the entire product lifecycle.
The GMP Guide for Natural Health Products Version 4.0 established substantially more detailed expectations for stability programs, documentation, quality systems, and oversight.
Health Canada’s proposed 2026 Quality of Natural Health Products Guide builds on this direction. The draft provides more detailed guidance around stability studies, packaging configurations, transportation, storage conditions, in-use periods, and consumer use after opening.
It also places greater emphasis on the relationship between stability testing and Finished Product Specifications, analytical methods, packaging compatibility, and ongoing post-market quality management.
Taken together, these developments reinforce an important shift: stability should not be treated simply as testing performed to print an expiry date on a product. It is part of the scientific evidence demonstrating that a product continues to meet appropriate quality standards throughout its commercial life.
Manufacturers, importers, and product licence holders should review their existing stability programs against Health Canada’s current GMP expectations and consider how the proposed Quality Guide could further affect their programs if finalized.
Organizations may wish to evaluate whether:
Companies developing new NHPs should consider these requirements early in product development. Stability studies can take months or years to complete, making early planning important for avoiding gaps in data later in the product lifecycle.
Stability testing is becoming an increasingly important component of Natural Health Product quality management in Canada. With Health Canada’s updated GMP requirements now in force and additional stability guidance proposed through the draft Quality of Natural Health Products Guide, manufacturers and importers are expected to maintain increasingly robust scientific evidence supporting product shelf life.
A well-designed program can do more than demonstrate compliance. It can help organizations understand how formulations, manufacturing processes, packaging, storage, and distribution affect product quality and provide evidence to support decisions throughout the product lifecycle.
dicentra supports Natural Health Product manufacturers, importers, and product licence holders with regulatory strategy, quality compliance, product licensing, Finished Product Specifications, GMP requirements, and stability program planning.
Whether you are developing a new product, reviewing an existing stability program, responding to Health Canada’s updated GMP expectations, or assessing how the proposed Quality Guide could affect your products, dicentra can help you identify gaps and develop a practical path forward.
Have questions about stability testing requirements for Natural Health Products? Contact dicentra to discuss your stability program and regulatory strategy.