Sig codes and prescription abbreviations

1 · Look up a sig code

What does that abbreviation mean?

Type a code as it is written on a prescription or an order (qhs, NPO, q4h, gtt), or a word from its meaning (bedtime, drops, each eye). Each answer gives the plain meaning, the Latin where there is one, where it is written, and any Joint Commission “Do Not Use” or ISMP error-prone flag with what to write instead.

140 codes in the list. The ones people look up most are answered below; search for any other.

2 · Where each code is written

How a sig line reads

The sig (Latin signa, write on label) is the directions part of a prescription: what the pharmacy prints on the label. Its codes usually come in the same order, so once the slots are familiar a sig line is easy to read. The examples name no drug and are for study only.

1. 1

   How often

   After the route in the sig: 1 tab PO bid.

2. 2

   When, and on what condition

   Usually the last part of the sig: 1 tab PO bid pc, 1 tab PO qhs, 1 cap PO q8h prn.

3. 3

   Route: how it goes in

   After the form in the sig: 1 tab PO bid, 2 gtt OU qid.

4. 4

   Form: what it is

   Right after the amount in the sig: 1 tab, 2 gtt, 1 supp.

5. 5

   Amount and units

   The first part of the sig, and the strength on the drug line: 10 mg, 5 mL, 2 gtt.

Outside the sig, the instruction words and symbols fill the rest of the prescription: the label line (sig), the quantity (disp), refills (non rep), substitution (DAW), and the compounding words (q.s., aa, M.).

• 1 tab PO bid pc

  • 1Amount and units
  • tabForm: what it is
  • PORoute: how it goes in
  • bidHow often
  • pcWhen, and on what condition

  Reads: one tablet by mouth, twice a day, after meals.

• 2 gtt OU qid

  • 2Amount and units
  • gttForm: what it is
  • OURoute: how it goes in
  • qidHow often

  Reads: two drops in each eye, four times a day.

  ISMP: write “each eye”, not OU, which is mistaken for AU (each ear).

• 1 cap PO q8h prn

  • 1Amount and units
  • capForm: what it is
  • PORoute: how it goes in
  • q8hHow often
  • prnWhen, and on what condition

  Reads: one capsule by mouth, every 8 hours, as needed (a prn direction also names the reason).

• ss tab PO qhs

  • ssAmount and units
  • tabForm: what it is
  • PORoute: how it goes in
  • qhsWhen, and on what condition

  Reads: half a tablet by mouth, every night at bedtime.

  ISMP: write “half tablet” in words (a handwritten ss has been read as 55), and QHS or qhs for bedtime, never HS.

3 · How often and when

The frequency and timing chart

Every “how often” and “when” code, with its Latin and how many doses that is in a day. The counts are arithmetic, not a schedule: a facility sets its own standard times, and qid (four doses in a day) is not the same as q6h (one dose every 6 hours).

4 · The safety list

The Joint Commission “Do Not Use” list

Applies to all orders and all medication-related documentation that is handwritten (including free-text computer entry) or on pre-printed forms. A trailing zero may be used only where it is needed to show the precision of a value, such as a lab result, an imaging size or a catheter or tube size; never in a medication order. ISMP keeps a longer list of error-prone abbreviations; the lookup above flags both.

5 · Practice questions

20 practice questions

The codes people look up most, the Latin behind them, where each is written and the two safety lists, multiple choice, one at a time. Every answer is explained, and your result is free: no sign-up needed.