What Does '5 mg qd' Mean on a Prescription?
On a prescription, "5 mg qd" is a shorthand instruction that means the patient should take 5 milligrams of the specified medication once a day [1.2.1, 1.2.3]. The "mg" stands for milligrams, a standard unit of mass for the dosage, while "qd" is a traditional medical abbreviation derived from the Latin phrase quaque die, which translates to "every day" or "once a day" [1.2.2, 1.2.9]. While historically common, the use of "qd" is now strongly discouraged by safety organizations to prevent medication errors.
The Dangers of Ambiguous Abbreviations: Why 'qd' is Risky
Patient safety organizations like The Joint Commission and the Institute for Safe Medication Practices (ISMP) have identified "qd" as an error-prone abbreviation and have placed it on their official "Do Not Use" lists [1.3.2, 1.6.1, 1.3.3]. The primary reason for this is the high potential for misinterpretation, which can lead to serious dosing errors [1.4.7].
The handwritten abbreviation "qd" can be easily mistaken for:
- q.i.d. (or QID): This stands for quater in die, the Latin term for "four times a day" [1.2.3]. Mistaking a once-daily medication for one that should be taken four times a day can lead to a dangerous overdose [1.5.8]. For example, a prescription for furosemide 40 mg once daily was misinterpreted as four times a day, resulting in a serious medical error [1.5.8].
- q.o.d. (or QOD): This stands for quaque altera die, meaning "every other day" [1.5.8]. Taking a medication daily when it should be taken every other day can also cause harmful side effects or toxicity.
- OD: This abbreviation can mean "once daily" but is also the Latin abbreviation for oculus dexter, meaning "right eye" [1.6.1]. This has led to cases where oral liquid medications were incorrectly administered into a patient's eye [1.6.1].
One study of medication errors reported between 2004 and 2006 found that the use of "QD" for "once daily" was the most common abbreviation associated with errors, accounting for 43.1% of all reported abbreviation-related mistakes [1.4.1, 1.4.4].
Best Practices: From 'qd' to 'Daily'
To enhance patient safety and ensure clarity, healthcare providers are now urged to write out the full word instead of using the abbreviation. The recommended best practice is to use "daily" or "once daily" [1.2.5, 1.3.3]. This eliminates ambiguity and significantly reduces the risk of a pharmacist, nurse, or patient misreading the prescription instructions. The Joint Commission has made compliance with its "Do Not Use" list a requirement for accredited healthcare organizations [1.3.2, 1.3.5].
Comparison of Similar-Looking Abbreviations
Understanding the distinctions between common but easily confused dosing frequency abbreviations is key to medication safety. Here is a table comparing them:
| Abbreviation | Latin Origin | Intended Meaning | Potential for Error |
|---|---|---|---|
| qd | quaque die | Once a day / Daily | Can be misread as 'qid' (four times a day) or 'qod' [1.2.5]. |
| qid | quater in die | Four times a day | Handwriting can make the 'i' look like the tail of a 'q' [1.6.1]. |
| qod | quaque altera die | Every other day | The 'o' can be mistaken for an 'i', leading to a 'qid' error [1.6.1]. |
| bid | bis in die | Twice a day | Less ambiguous, but clarity is always preferred [1.2.3]. |
| tid | ter in die | Three times a day | Less ambiguous, but clarity is always preferred [1.2.3]. |
Other Common Prescription Abbreviations
Besides dosing frequency, prescriptions often contain other shorthand. Here are a few common ones:
- po: From the Latin per os, meaning "by mouth" or "orally" [1.2.6, 1.5.9].
- prn: From the Latin pro re nata, meaning "as needed" [1.5.9]. This is used for medications taken only when symptoms are present, such as pain relievers.
- ac / pc: From the Latin ante cibum ("before meals") and post cibum ("after meals") [1.5.9].
- hs: From the Latin hora somni, meaning "at bedtime" [1.5.9]. This is also an error-prone abbreviation, as it can be confused with "half-strength" [1.5.8].
- Rx: An abbreviation for the Latin word recipere, meaning "to take." It symbolizes a medical prescription [1.5.8].
Conclusion: Your Role in Medication Safety
While healthcare systems work to phase out dangerous abbreviations, patients play a vital role in ensuring their own safety. Always review your medication labels. If you see an abbreviation you don't understand or instructions that seem unclear, do not hesitate to ask your doctor or pharmacist for clarification. Confirming the medication's name, dose, frequency, and route of administration is a simple but powerful way to prevent errors and ensure you get the full benefit of your treatment. When in doubt, always ask.
For more information on safe medication practices, you can visit the Institute for Safe Medication Practices (ISMP).
