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Sig codes on the PTCE, and the ones you must never write

Sig codes appear in two domains and the exam wants different work from you in each. Order Entry and Processing asks you to translate them onto a label. Patient Safety and Quality Assurance asks which ones should never have been written at all, and several codes, including HS, OD and ud, sit on both lists at once.

Published September 4, 2026

A prescription reading 'caps ii PO q4h prn pain' is asking you to do one job. A medication order reading 'insulin 10 U' is asking you to do a different one, and that second job is to notice the order should never have been written that way. Both kinds of question appear on the PTCE, sitting in separate domains, and a candidate who studies only the translation half is leaving the safety half unprepared.

The translation half

Order Entry and Processing is where you turn shorthand into a label a patient can follow. The abbreviations divide into route, timing, form and quantity, and the quantity one catches people out because it is written in Roman numerals rather than digits.

Eye and ear abbreviations are their own trap because the two sets look alike and mean different organs. OD, OS and OU are the right eye, the left eye and both eyes. AD, AS and AU are the right ear, the left ear and both ears. A sig reading 'gtt iii AS bid' becomes three drops into the left ear twice daily, and a candidate who reads that S as an eye has produced a label that sends medication to the wrong place.

The safety half

Patient Safety and Quality Assurance asks a different question about the same shorthand. The glossary entry that matters here is error-prone abbreviations: shorthand that the Institute for Safe Medication Practices says to spell out because handwriting turns it into something else. The Joint Commission maintains a shorter official Do Not Use list covering the same ground.

Two decimal rules belong to the same family and get asked directly. A trailing zero is prohibited because warfarin 5.0 mg reads as 50 mg the moment the decimal point is lost. A leading zero is required for the opposite reason, so half a milligram is written 0.5 mg and never .5 mg, and both rules exist because a missing mark on paper multiplies a dose by ten.

Tall man lettering is the same idea applied to drug names rather than to doses. hydrALAZINE and hydrOXYzine, predniSONE and predniSOLONE, DOPamine and DOBUTamine: the capitals sit in the middle because that is where the names differ, and they do their work on shelf labels and selection screens at the moment somebody picks a product.

The codes that are on both lists

This is where the two halves collide, and it is worth knowing before you meet it in a question. HS, OD, OS, OU and ud all appear in the translation tables that every study guide prints, and all of them also appear on the ISMP error-prone list. HS can be read as half-strength. OD can be read as once daily rather than as the right eye. You are expected to know what they mean and to know they should not be written.

That is not a contradiction in the exam so much as a description of the job. Prescriptions arrive carrying shorthand that a pharmacy did not choose, and a technician has to read what came in while recognizing which parts of it need clarifying with the prescriber. An order written 'insulin 10 U' gets clarified rather than guessed, and that clarification is itself an answer the exam asks for.

How to study this without a list

The translation half rewards drilling because the codes are arbitrary and there are perhaps forty of them worth knowing. The safety half rewards understanding the failure instead, because every entry on the error-prone list has a specific misreading behind it and the misreading is the answer. Ask what this looks like in bad handwriting, and most of the list stops needing memorization.

Our free practice test draws from both domains in the proportions the 2026 outline sets, so sig questions and error-prone questions arrive mixed rather than grouped. The blueprint guide breaks down how much each domain is worth, and the glossary carries the full set of abbreviations with the ISMP notes attached.

Related

• The 2026 PTCE blueprint, domain by domain
• Pharmacy math for the PTCE: what is actually tested in 2026
• Federal Requirements is now nearly a fifth of the PTCE