Medical abbreviations and symbols
What the abbreviations on prescription labels and medical charts stand for, and the emblems of medical and emergency services.
This collection explains the shorthand and emblems people meet on prescription labels, in medical records and on ambulances: prescription abbreviations such as PRN and BID, medical chart abbreviations such as EtOH and PERRLA, and medical and emergency emblems such as the Star of Life. The pages say what each one stands for and who uses it, and give no doses and no advice.
The Latin shorthand on prescriptions and medicine labels, such as PRN, BID and PO, and what each one stands for.
Shorthand found in medical records and discharge notes, such as EtOH, PERRLA and ADL, and what each one stands for.
The emblems on ambulances, medical alert jewellery and in armed conflict, what each one marks, and who may use it.
Prescription abbreviations
Most prescription shorthand is abbreviated Latin. PRN is pro re nata, “as needed”, and BID is bis in die, “twice a day”, in the American Heritage Dictionary’s entries, and MedlinePlus lists PRN, BID, TID and QID as abbreviations a doctor may write on a prescription. Some forms are flagged as error-prone. QD, for every day, is on the Joint Commission’s “Do Not Use” list because it is mistaken for QOD, and the Institute for Safe Medication Practices’ list says it is mistaken for q.i.d., four times a day. The Rx page covers the ℞ sign, which the American Heritage Dictionary derives from the Latin recipe.
Chart abbreviations
Notes in a medical record use a different shorthand, and each institution approves its own list of it: Charleston Area Medical Center, the North Carolina College of Emergency Physicians, the Central California EMS Agency and California Correctional Health Care Services among them. Their meanings overlap and sometimes differ: ASA is aspirin on these lists, and also the American Society of Anesthesiologists, whose physical status classes run from ASA I to ASA VI. Each page names whose list gives which reading.
Emblems and their snakes
The Star of Life is the blue six-barred emblem that the US National Highway Traffic Safety Administration holds as a certification mark for emergency medical services. The medical alert symbol on ID jewellery tells first responders the wearer has health information to read. The red cross, with the red crescent and red crystal, protects medical services and relief workers in armed conflict, and the ICRC’s leaflet on misuse lists a pharmacy’s shopfront sign among the displays it does not authorize.
The snake on a staff at the centre of the Star of Life is the rod of Asclepius, EMS.gov says. The MedicAlert Foundation’s UK guide says the caduceus, two snakes crossing round a winged staff, is often mistaken for it. How the two came to medicine, and why the US Army took the caduceus, is on oldsymbols.com’s page on symbols of medicine.
Sources
- p.r.n. (American Heritage Dictionary entry), The American Heritage Dictionary of the English Language, Fifth Edition, HarperCollins Publishers, p.r.n., abbr.
- b.i.d. (American Heritage Dictionary entry), The American Heritage Dictionary of the English Language, Fifth Edition, HarperCollins Publishers, b.i.d., abbr.
- Appendix B: Some Common Abbreviations, MedlinePlus, U.S. National Library of Medicine, PRN
- Facts about the “Do Not Use” list, The Joint Commission, fact sheet: Official “Do Not Use” List, The Joint Commission, Official “Do Not Use” List table; Development of the “Do Not Use” List (page as archived 19 January 2022)
- ISMP List of Error-Prone Abbreviations, Symbols, and Dose Designations (2024), 2024 edition, Institute for Safe Medication Practices, Abbreviations for Frequency/Instructions for Use: o.d., QD, QOD, q1d
- Rx (American Heritage Dictionary entry), The American Heritage Dictionary of the English Language, Fifth Edition, HarperCollins Publishers, Rx, n.
- Abbreviations Approved for Medical Records, Charleston Area Medical Center, A
- Statement on ASA Physical Status Classification System, Last amended 13 December 2020 (original approval 15 October 2014), American Society of Anesthesiologists, Current definitions
- EMS Star of Life, EMS.gov, Office of EMS, National Highway Traffic Safety Administration, Page text
- Criteria for Use of Blue “Star of Life” for Emergency Medical Services, Federal Register vol. 59, no. 154, 11 August 1994 (FR Doc. 94-19562), National Highway Traffic Safety Administration, via GovInfo, NHTSA’s Authority; Other Issues Raised; Appendix A
- Medical Symbols and Their Meaning: The 2026 Guide, Reviewed by Emma Brewer, registered nurse, MedicAlert Foundation (UK), Article; FAQ
- Use of emblems, Law and policy, International Committee of the Red Cross, Page text
- Red Cross and Red Crescent Emblems: Safeguarding Their Power to Protect and Preventing Misuse, Leaflet, International Committee of the Red Cross, via the ICRC New Delhi resource centre, pp. 1, 4–5
Last reviewed September 30, 2026 by Rory Hansen. How we research