Is The Expiration Date For A Drug The First Or Last Day Of The Month?
In our latest question and answer, the pharmacist discusses whether the expiration date listed on a drug bottle is the first of late day of the month.

Question
I'm hoping you can help me with a question that I just cannot find the answer to. I work in a pharmacy and I noticed that most drugs have an expiration date listed as month and year (e.g. 3/2023). Does this mean that the drug expired on the first of the month or on the last day of the month?

Answered by Dr. Brian Staiger, PharmD
Medical Content Reviewed By HelloPharmacist
Staff
Last updated Apr 09, 2025
Key points
- If a manufacturer's drug bottle lists an expiration date as a month and year (e.g. 3/2023), the expiration date is the last day of the listed month, per the USP (United States Pharmacopeia)
- The USP (United States Pharmacopeia) is the official compendia under federal law, and works closely with the FDA (Food and Drug Administration)
Quick Answer
In regard to drugs, if an expiration date only has the month and year listed (e.g., 03/2023), the intended expiration date is the last day of the month, not the first day. In other words, the drug would be 'good through 03/31/2023'.
Detailed Answer
Hello and thanks for reaching out! I've been answering questions from our readers and writing articles for many years now (since 2012) and the question I most often get from fellow pharmacists concerns the expiration date listed on drug bottles (i.e. manufacturer drug bottle).
Specifically, I get asked whether or not the expiration date listed (typically the month and year only) refers to the first day of the month or the last. For example, does an expiration date of 3/2023 mean it expires on March 1st, 2023, or March 31st, 2023?
The answer is that the expiration date on the manufacturer's drug bottle, when listed as a month and year, refers to the last day of the listed month. So, from the example above of 3/2023, the implied expiration date is March 31st, 2023.
Why Is There Confusion?
I can certainly understand the confusion. Unlike food products, which typically list a specific day, drug bottles often only list the month and year. I can't recall ever learning definitively in pharmacy school, or in practice for that matter when a drug actually expires based on the date listed.
Even the FDA Code of Federal Regulations Title 21, which discusses packaging and labeling, is ambiguous:
(a) To assure that a drug product meets applicable standards of identity, strength, quality, and purity at the time of use, it shall bear an expiration date determined by appropriate stability testing described in § 211.166.
(b) Expiration dates shall be related to any storage conditions stated on the labeling, as determined by stability studies described in § 211.166
So, if the FDA (Food and Drug Administration) doesn't provide definitive guidance, where do we turn to determine the exact expiration date? The answer is the USP (United States Pharmacopeia).
USP Defined Drug Expiration
The USP establishes standards for medicines and works in close collaboration with the FDA. This relationship dates all the way back to 1906 when the Pure Food and Drug Act listed the United States Pharmacopeia as the official compendia under federal law.
The USP states the following regarding drug expiration dates:
The expiration date limits the time during which the article may be dispensed or used. If an expiration date is stated only in terms of the month and the year, then the intended expiration date is the last day of the stated month.
So, there you have it, an expiration date on a manufacturer drug bottle, when only listed as the month and year, is the last day of the month.
I do want to point out that this only refers to a manufacturer's 'stock' bottle, stored in proper conditions, in a pharmacy or distributor. It doesn't necessarily apply to a drug that has been dispensed to a patient (which is usually one year from dispensing based on the laws in your state but can vary).
Final Words
Thanks again for reaching out to us!
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Dr. Brian Staiger, PharmD
- 28837 views