Safeguard Use of Sig Codes and Mnemonics

Author: Michael J. Gaunt, PharmD

Sig codes and mnemonics save time behind the counter, but careless mistakes and misinterpretation can lead to serious medication errors.


Many pharmacies use sig (or speed) codes and mnemonics to ease and accelerate the data entry process. Sig codes are programmed into the pharmacy computer system and used to represent a specific set of directions. For example, a computer system could be programmed so that the sig code “1TBID” will produce “Take 1 tablet by mouth twice daily” on the pharmacy label. Mnemonics are programmed to represent a specific drug and dosage strength combination. For example, “LIP20” could be used to represent Lipitor 20 mg.

Although these codes can save time, they are not without risk. Below are 2 examples reported to the Institute for Safe Medication Practices (ISMP) National Medication Errors Reporting Program that illustrate how processes involving sig codes can contribute to medication errors.

A physician prescribed the nonsteroidal anti-inflammatory drug diclofenac 75 mg with instructions to “Take 1 tablet twice daily with food for shoulder and elbow pain.” However, the pharmacy dispensed the prescription with the instructions to “Take 1 tablet daily with food for shoulder and elbow pain.” The error was discovered when dispensing the first refill. Luckily, the patient had been taking the prescription correctly despite the incorrect label.

The reporter noted that distractions during the original verification phase contributed to the error. More significantly, the pharmacy identified that the sig code that was used did not produce the expected translation. Instead of producing “Take 1 tablet twice daily with food” the sig code placed “Take 1 tablet daily with food” on the label. When the sig code had been originally programmed into the pharmacy computer system, the wrong directions were associated with it.

In a similar report from a different pharmacy, the directions for the oral contraceptive Tri-Sprintec (ethinyl estradiol and norgestimate) were entered incorrectly. The directions should have been “Take 1 tablet daily for dysmenorrhea,” but instead the prescription was labeled “Take 1 tablet daily for dyspepsia.” Upon investigation, the pharmacy discovered that the sig code “dys” had been created as a short cut for dyspepsia. However, the technician believed it to represent dysmenorrhea. The technician entered “dys” during data entry and the translation to dyspepsia was not caught by the verification pharmacist, nor was it caught during 2 subsequent refills.

Safe Practice Recommendations

In order to reduce the risk of medication errors resulting from vulnerable sig codes and mnemonics, consider the following strategies:


Dr. Gaunt is a medication safety analyst and the editor of ISMP Medication Safety Alert! Community/Ambulatory Care Edition.