How drug expiration dates are set

In 1979, FDA began requiring an expiration date on prescription and over-the-counter medicines, the agency says¹. The regulation behind it, 21 CFR 211.137², is short. A drug product "shall bear an expiration date determined by appropriate stability testing," and the date must be "related to any storage conditions stated on the labeling."

That date marks the end of the period a manufacturer has shown, with data, that a product stays within its specifications for identity, strength, quality and purity when stored as labeled. Federal testing has found that many properly stored products stay within specification well past their labels, and that the extra time varies so much from lot to lot that it can only be known by testing each lot.

That distinction matters most during shortages, when FDA has repeatedly allowed specific lots to be used past their labeled dates on the strength of new data. None of it applies to medicine in a household cabinet. FDA's consumer guidance says that once the date has passed "there is no guarantee that the medicine will be safe and effective," and questions about a specific medicine are for a pharmacist.

How a manufacturer arrives at a date

Expiration dating sits inside the current good manufacturing practice rules, the CGMP framework our explainer on CGMP covers. A companion regulation, 21 CFR 211.166³, requires a written stability testing program for every drug product, and says its results "shall be used in determining appropriate storage conditions and expiration dates."

That program has to specify sample sizes and test intervals "based on statistical criteria," storage conditions for retained samples, "reliable, meaningful, and specific test methods," and testing in the same container and closure the drug is sold in. A pill tested in a glass jar tells you little about the same pill in a plastic bottle.

Section 211.166 also allows a shortcut, with conditions. Accelerated studies, run at higher temperature and humidity, "may be used to support tentative expiration dates" while full-length studies continue. If the tentative date goes beyond what real-time data support, the manufacturer must keep testing until the date is verified or corrected.

The test conditions, in numbers

Most manufacturers follow the international stability guideline known as ICH Q1A(R2), which FDA publishes as guidance⁴. It sets standard storage conditions and the minimum time on test at the point an application is filed.

Source: ICH Q1A(R2) as published by FDA. The guideline calls for data on at least three primary batches.

Generic drugs follow the same science on a slightly shorter runway. A 2013 FDA guidance says applicants should submit data from "three pilot scale batches or two pilot scale batches and one small scale batch" and, at filing, "provide 6 months of data that include accelerated and long-term conditions," according to the document⁵. Our explainer on how a generic drug gets approved places stability data within the wider application.

A date can be lengthened later. A manufacturer of an approved drug may extend the expiration date "based on acceptable data from full, long-term stability studies on at least three pilot or production batches in accordance with a protocol approved in the NDA or ANDA," FDA says⁶.

What the Shelf Life Extension Program found

Federal agencies hold large stockpiles of drugs for military and public health emergencies. Replacing them every few years is expensive, so in 1986 the government set up the Shelf Life Extension Program, or SLEP. It is run by the Department of Defense; FDA does the testing and decides on extensions, according to FDA⁶.

SLEP is fee-for-service and "remains limited to federal stockpiles at this time." Testing focuses on military-significant products, drugs with little commercial use such as nerve agent antidotes, and drugs bought in very large quantities, such as ciprofloxacin and doxycycline.

SLEP's records are among the largest bodies of drug stability data anywhere. A 2006 paper by FDA scientists reviewed 122 drug products and 3,005 lots tested under SLEP. It found that 88 percent of lots were extended at least one year past their original date, with an average extension of 66 months. The authors added a caution that is easy to skip. "Due to the lot-to-lot variability, the stability and quality of extended drug products can only be assured by periodic testing and systematic evaluation of each lot," they wrote in the Journal of Pharmaceutical Sciences⁷.

Since 2013, section 564A(b) of the FD&C Act has also given FDA explicit authority to extend dating for stockpiled products meant for chemical, biological, radiological or nuclear emergencies, with conditions on storage, testing and labeling, FDA says⁶.

Extended use dates during shortages

Outside stockpiles, FDA's main tool is a public table. "Based on stability data provided by the manufacturers and reviewed by FDA," the agency lists specific lot numbers that may be used through a new date, on its extended use dates page⁸. FDA says it is not requiring or recommending relabeling, and if replacement product becomes available during the extension period, it "expects the lots in these tables will be replaced and properly disposed of as soon as possible."

GxRadar tallied the table as it stood on Oct. 20, 2026, grouping lots by product and measuring the gap between labeled and extended dates.

Source: GxRadar analysis of FDA's Search List of Extended Use Dates to Assist with Drug Shortages, content current as of Oct. 20, 2026. The three dextrose lots each appear under two package codes. Extensions rounded to whole months.

All four are injectables, the category that dominates FDA's shortage list for reasons our piece on sterile injectable shortages lays out. The same tool came into play during the IV fluid shortage that began in 2024. In August 2025 FDA's commissioner listed reviews to "extend product expiry" among the steps that ended the saline shortage, in his statement⁹. Our account of the 2024 IV fluid shortage has the full sequence, including the hurricane damage that set it off.

Storage, labels and the pharmacy counter

Every one of these extensions depends on storage. FDA's consumer page warns that improper storage, such as in a damp bathroom cabinet, "can contribute to decreased effectiveness in medicines that have not reached their posted expiration date," and suggests a cool, dry place. Our explainer on storage instructions on medicine labels decodes the wording. SLEP's results apply to climate-controlled federal warehouses.

The date on a pharmacy label can also differ from the manufacturer's date on the stock bottle, especially when a pharmacist repackages or mixes a product. Our guides on how to read a prescription label and where the lot number and expiration date sit on a package cover where each date appears, and a pharmacist can say which one governs a particular prescription.

Several lots on FDA's current extended-use list carry new dates running into 2027, the latest Oct. 31, 2027.