How to read a prescription: common abbreviations explained
Last reviewed 23 October 2026
Short answer: Doctors often write prescriptions in shorthand, such as Tab for tablet, BD for twice a day and SOS for "if needed". This page explains the most common abbreviations so you can understand what is written. It is for understanding only. Always confirm how to take your medicine with your doctor or pharmacist.
Why prescriptions use abbreviations
Many of the abbreviations come from Latin and have been used by doctors for a long time. They save writing time, but they can confuse patients, and handwriting can make them harder to read. Do not try to guess. If you cannot read or understand something on a prescription, ask the pharmacist to explain it before you leave the shop.
What the medicine is: form and route
| Written as | Meaning |
|---|---|
| Rx | "Take" or "prescription". It often appears at the top of the medicine list. |
| Tab | Tablet |
| Cap | Capsule |
| Syp or Susp | Syrup or suspension (a liquid medicine) |
| Inj | Injection |
| Oint or Cream | Ointment or cream, applied to the skin |
| Drops | Drops, for the eye, ear or nose, or to take by mouth. Check which. |
| mg, g, ml | Milligram, gram and millilitre, the units of strength and volume |
A strength such as "500mg" is part of the product. A different strength is a different product, so make sure the pack matches what is written. See how to read a medicine label.
How often: frequency
| Written as | Meaning |
|---|---|
| OD | Once a day |
| BD or BID | Twice a day |
| TDS or TID | Three times a day |
| QID | Four times a day |
| HS | At bedtime |
| SOS or PRN | Only when needed, for example for pain. Ask how often and how many in a day you may take. |
| Stat | Immediately, as a single first dose |
Take care with "OD". On eye medicines, "OD" can mean the right eye, so ask the pharmacist if you are unsure, especially with eye drops. Where a prescription gives a number of days, such as "x 5 days", that is how long to take the medicine.
When in relation to food
| Written as | Meaning |
|---|---|
| AC | Before meals |
| PC | After meals |
| With food or after food | Take with or just after a meal, which can reduce stomach upset for some medicines |
| Empty stomach | Usually means about an hour before or two hours after food. Ask the pharmacist to be precise. |
Reading a sample line
Suppose a prescription says: Tab X 500mg, 1 BD, PC, x 5 days. In plain words it means: one tablet of X, 500mg strength, twice a day, after meals, for five days. This is only an example of how to read the shorthand. It is not a recommendation for any medicine. "X" is a made-up name used for illustration.
Check these things before you leave the pharmacy
- The names, strengths and forms on the pack match what is written on the prescription.
- You know how many times a day to take each medicine, and for how many days.
- You know whether to take it before or after food.
- You know what to do if you miss a dose, and what side effects to watch for.
- The expiry date is well ahead. See medicine expiry dates explained.
Our list of 10 questions to ask your pharmacist will help you at the counter.
If you want to change a brand to save money
Do not change a brand, strength or form on your own. A pharmacist can often suggest a registered alternative with the same ingredient and strength, but for a prescribed medicine, check with your doctor first. Read brand vs generic medicines for what to compare.
Frequently asked questions
What if I cannot read my doctor's handwriting?
Ask the pharmacist, and if they are not certain, ask them to check with the doctor. Do not guess the name or the dose of a medicine.
Does "SOS" mean I can take as much as I like?
No. It means "if needed", not "without limit". Ask your doctor or pharmacist how often you may take it and the most you can take in a day.
Can a pharmacist explain my prescription to me?
Yes. Explaining how to take a prescribed medicine is an important part of a pharmacist's work.
Sources and further reading
- Your doctor or pharmacist, who can confirm how to take your own medicines.
- The label and leaflet supplied with each medicine.
- DRAP, dra.gov.pk, for official information on registered medicines.