How to read your prescription: a simple guide to common abbreviations
OD, BD, TDS, SOS. Doctors use shorthand on prescriptions. Here's what the most common terms mean so you take your medicines the right way.
Medisri Team22 October 2026 5 min read
Key takeaways
- Abbreviations tell you how often and when to take each medicine.
- "Before food" and "after food" matter: some medicines work differently with a meal.
- If anything is unclear, ask your doctor or pharmacist before you start.
Prescriptions are written quickly and often use short forms that come from Latin. Once you know the common ones, a prescription becomes much easier to follow.
How often to take it
- OD: once a day.
- BD (or BID): twice a day.
- TDS (or TID): three times a day.
- QID: four times a day.
- SOS (or PRN): only when needed, for example for pain or fever.
- Stat: immediately, as a single dose.
When to take it
- AC: before food.
- PC: after food.
- HS: at bedtime.
Reading the rest of the prescription
Next to each medicine you'll usually see the strength (for example 500 mg), the dose (for example 1 tablet) and the duration (for example 5 days). A pattern like 1-0-1 means one dose in the morning, none in the afternoon and one at night.
Not sure about a word or a dose? Don't guess. Your pharmacist can explain the prescription before you take the first dose.
A few good habits
- Keep your prescription until the course is complete.
- Tell your doctor about any other medicines or supplements you take.
- Don't change the dose or stop early without checking with your doctor.
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