Sig code: frequency

PRN medical abbreviation

PRN means "as needed", from the Latin "pro re nata".

Each meaning matched at least two public references (5 in all for PRN), checked October 23, 2026. The table lists them.

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Meaning	Latin origin	Where used	Checked against
as needed	pro re nata	Prescriptions, Medication labels	MedlinePlus Appendix B: Some Common Abbreviations (NLM) NCI Thesaurus, including CDISC SDTM terminology (NCI EVS) NLM SPECIALIST Lexicon abbreviations file (LRABR) FDA Acronyms and Abbreviations Army Regulation 40-66, Appendix B: Authorized Medical Records Abbreviations

Also written: p.r.n.

Sig line on a practice handout: "take by mouth PRN."

A made-up line that shows the abbreviation in place. It is not about any patient and is not an instruction.

What does PRN mean in medical terms?

PRN means "as needed", from the Latin "pro re nata".

What does PRN stand for in Latin?

PRN comes from "pro re nata", meaning "as needed".

Where is PRN used?

PRN shows up in prescriptions and medication labels. Its category here is sig code: frequency.

Is PRN on the Joint Commission Do Not Use list?

No. PRN is not on the Joint Commission Do Not Use list or the ISMP error-prone list as checked on October 23, 2026.