In brief
A stability study has no fixed price, because it consists of many individual building blocks that differ greatly from product to product. Anyone who puts two quotations side by side and looks only at the total is therefore often comparing two different studies. It is more helpful to know the cost drivers and to give the laboratory a study protocol, or at least a precise description, so that all providers calculate on the same basis.
Roughly speaking, the costs fall into three parts: storage of the samples over the entire duration, testing at the individual time points, and the work before and after, that is, methods, protocol and reports. Which part dominates depends on the product and the purpose of the study.
Study design as the biggest lever
Most costs are already fixed before the first sample goes into the climatic chamber, namely with the study design. For registration studies, the ICH guidelines set the framework, and this determines the main quantities. In 2025, ICH published a draft revision that consolidates the previous Q1 guidelines; until it enters into force, the guidelines listed here apply.
Number of batches
Each batch is tested at every time point and under every condition. The number of batches therefore has a direct effect on almost all other items. For a marketing authorisation, ICH Q1A(R2) requires data from at least three batches; for a development study or a study following a minor change, fewer may be sufficient. If several strengths or pack sizes are added, the scope multiplies accordingly, unless bracketing or matrixing under ICH Q1D is used.
Storage conditions
A long-term condition and an accelerated condition are usual, and depending on the results also an intermediate condition. If the product is to be marketed in countries with a hotter or more humid climate, other long-term conditions are added. Every additional condition occupies space in a qualified climatic chamber and generates its own time points. Refrigerated or frozen storage and photostability testing under ICH Q1B are separate items.
Time points and duration
The duration depends on the shelf life you want to claim and can be several years. For long-term storage, ICH Q1A(R2) generally provides for a time point every three months in the first year, every six months in the second year and annually thereafter. Storage costs accrue over the entire period, and many laboratories charge them monthly or per time point. The number of time points is usually the strongest single driver, because at each time point the planned test programme is run for every batch and every condition.
What is tested at each time point
The test scope at each time point follows from the product specification. For a tablet, this typically includes appearance, assay, degradation products, dissolution and water content; for a sterile solution, sterility, particulate matter or endotoxins are added, for example; and for a biological active substance, more complex methods for purity and potency. The more tests and the more complex the individual method, the more expensive each time point becomes.
It is worth discussing with the laboratory whether all parameters really need to be tested at every time point. Some tests can be limited to selected time points on a justified basis. This should, however, be scientifically justified and recorded in the protocol, because the authority will later see the design in the marketing authorisation dossier.
Methods, samples and reports
Method development and validation
If you provide validated, stability-indicating methods, the laboratory usually only has to adopt them and document the transfer. If such methods are lacking, development and validation under ICH Q2(R2) are added, often including stress studies that show the method reliably detects degradation products. For new products this part can account for a large share of the total costs, and it is often shown separately in quotations, but sometimes simply assumed to be in place.
Sample quantity
The required sample quantity follows from the test scope, the time points and a reserve for repeat tests. For you, this is mainly a cost factor with expensive material or small batches; for the laboratory, it concerns storage, labelling and sample management. Clarify how much reserve material is planned and what happens to unused samples at the end.
Protocol and reports
The study protocol, interim reports after individual time points, trend analyses and the final report take time. Some laboratories provide only certificates of analysis for each time point and charge separately for detailed reports or a statistical evaluation of shelf life under ICH Q1E. If you need the results in a specific format for the marketing authorisation dossier, say so in your request.
Changes during the study
A stability study runs over a long period, and during this time things often change. A specification is adjusted, a method is revised, an additional time point is needed or an out-of-specification result has to be investigated. Each of these changes means work that is usually not included in the original quotation. Ask, therefore, how the laboratory charges for protocol amendments, additional tests and investigations of deviations, and whether there are conditions for terminating the study early.
Making quotations comparable
Quotations can only be compared if all laboratories work with the same assumptions. A three-step approach has proven useful:
Finding suitable providers
Laboratories offering stability studies can be found in our directory under Stability testing. If you also need methods developed or validated, it is worth looking at the providers of Contract analytical testing.