When pharmacy students start reading prescriptions for the first time, one thing becomes obvious very quickly that abbreviations are everywhere. Doctors rarely write full instructions. Instead, they use short Latin-based terms to save time and space. This is fine for experienced professionals, but for students and interns, these abbreviations can be confusing. If misunderstood, they can lead to serious medication errors. That is why learning prescription abbreviations is not optional. Whether you are preparing for D. Pharmacy exams, GPAT, hospital training, or real-life dispensing, these terms appear again and again. Below are the 10 most important prescription abbreviations, explained in simple language with examples and clinical relevance.
1. OD (Once a Day): OD comes from the Latin term Omni Die, which means once daily.
Example: Take 1 tablet OD after food.
Important caution: OD can also mean right eye (oculus dexter) in ophthalmic prescriptions.
Always check the dosage form, route, and context. Confusing these meanings can cause serious errors.
2. BD (Twice a Day): BD is derived from Bis in Die, meaning twice daily. These doses are usually given 12 hours apart.
Example: Amoxicillin 500 mg BD (One tablet in the morning and one in the evening)
This abbreviation is extremely common in antibiotic prescriptions.
3. TDS (Three Times a Day): TDS stands for Ter in Die, meaning three times daily.
Example: Paracetamol TDS (Usually taken every 8 hours)
This abbreviation is frequently used for analgesics and antipyretics.
4. QID (Four Times a Day): QID comes from Quarter in Die, which means four times daily.
Example: Metronidazole QID (Approximately every 6 hours)
Because of frequent dosing, patients need proper counselling to maintain compliance.
5. HS (At Bedtime): HS is derived from Hora Somni, meaning at bedtime.
Example: Cetirizine 10 mg HS
Drugs that cause sedation or drowsiness are commonly prescribed at bedtime to minimize daytime side effects.
6. SOS (If Required): SOS comes from Si Opus Sit, meaning if required.
Example: Ibuprofen 400 mg SOS for pain.
Clinical note: Many patients misunderstand SOS as “emergency use.” Because of this confusion, several hospitals now prefer using PRN, which is clearer.
7. PO (By Mouth or Oral Route): PO is derived from Per Os, meaning by mouth.
Example: Tablet PO BD (Take orally, twice daily)
Before dispensing, always confirm that the patient can swallow and tolerate oral medication, especially in hospitalized patients.
8. IV (Intravenous): IV refers to drug administration directly into a vein.
Example: Inj. Ceftriaxone 1 g IV BD
The intravenous route provides rapid drug action and is commonly used in emergencies and severe infections.
9. PRN (As Needed): PRN comes from Pro Re Nata, meaning as needed.
Example: Salbutamol inhaler PRN.
PRN vs SOS: PRN is generally used for ongoing conditions, while SOS is more situational. PRN is considered safer and clearer in modern clinical practice.
10. SC (Subcutaneous): SC means subcutaneous injection, given just beneath the skin.
Example: Insulin injections are administered SC before meals.
This route provides slow and sustained absorption, making it ideal for insulin and certain vaccines.
Why Prescription Abbreviations Are So Important in Pharmacy
Learning prescription abbreviations is not just about clearing exams. It is about patient safety.
A single mistake in understanding an abbreviation can result in:
1) Wrong dose
2) Wrong route
3) Wrong frequency
4) Serious patient harm
For pharmacy students, mastering these abbreviations helps you:
1) Reduce medication errors during internships
2) Read prescriptions confidently
3) Communicate effectively with doctors and nurses
4) Perform better in viva voce and case discussions
If you are serious about becoming a competent pharmacist, these abbreviations should be second nature to you.
For MCQ’s practice you can visit Pharma Unit MCQ’s section.