Most prescriptions in India are written in a shorthand that has not changed much in a century. It is not meant to confuse you, but it does — and getting the timing wrong is one of the commonest reasons a medicine does not work as it should. Here is what the abbreviations actually mean.

The symbols at the top

Rx comes from the Latin recipe, meaning “take”. Everything written after it is what the doctor wants dispensed. Sig or S introduces the instructions meant for you rather than for the pharmacist.

How often to take it

• OD — once a day
• BD or BID — twice a day, roughly 12 hours apart
• TDS or TID — three times a day, roughly 8 hours apart
• QID — four times a day
• HS — at bedtime
• SOS or PRN — only when needed
• STAT — immediately, one dose now

The gaps matter more than people think. BD does not mean breakfast and dinner if your breakfast is at 7 and dinner is at 9 — that is a 14-hour gap and a 10-hour one. For antibiotics especially, spacing doses evenly is what keeps the drug level steady enough to work.

Before or after food

• AC — before food, usually 30–60 minutes before
• PC — after food
• NPO — nothing by mouth

Some medicines genuinely need an empty stomach to be absorbed — levothyroxine and most proton pump inhibitors like pantoprazole are the usual examples. Others are written PC simply because they upset the stomach. If in doubt, ask; it is a two-second question with a real effect on how well the medicine works.

How it goes in

PO by mouth, IM into muscle, IV into a vein, SC under the skin, OD/OS/OU right eye, left eye, both eyes, PV and PR vaginal and rectal.

Note the trap: OD means “once daily” in a dosing instruction but “right eye” in an eye-drop instruction. Context decides, which is exactly why you should never guess.

Quantities

1 tab, 1 cap, 1 tsp (5 ml), 1 tbsp (15 ml). Use the measuring cup that comes with a syrup, not a kitchen spoon — household teaspoons vary between about 3 and 7 ml, which is a serious difference for a child.

“Continue for 5 days” means five days

The commonest and most damaging habit we see is stopping an antibiotic once the fever settles, usually around day three. The bacteria that survive that partial course are the hardest ones to kill, and the next infection is harder to treat. Finish the course unless the doctor tells you otherwise.

If you cannot read it, ask

Handwriting is a genuine safety issue, and no pharmacist worth the licence will guess at an unclear prescription. We phone the prescriber when something is ambiguous. If you would like your prescription explained — what each medicine is for, when to take it, what to watch out for — bring it in or send a photo on WhatsApp. There is no charge for that.

Written by Roshan Kumar Gupta, registered pharmacist (Reg. No. 38441/OPC, Odisha Pharmacy Council) and proprietor of Gupta Meds, CDA Sector 13, Cuttack.

This article is general information, not a substitute for a consultation. Always follow the advice of your own doctor or pharmacist for your specific situation.

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