OD BD TDS meaning: prescription abbreviations decoded
The OD BD TDS meaning is simple: OD means once a day, BD means twice a day and TDS means three times a day. These Latin-based short forms tell you how often to take a medicine, while others like SOS (only if needed), HS (at bedtime), AC (before food) and PC (after food) tell you when. If any short form on your prescription is unclear, ask the doctor or pharmacist before the first dose.
OD BD TDS meaning: the core frequency codes
Prescription abbreviations come from Latin, the old language of medicine. Indian doctors still use them daily because they are quick to write. Knowing the OD BD TDS meaning is as basic to family health as knowing how to read medical reports, because the right medicine at the wrong frequency can fail or cause harm.
OD: once daily
OD comes from "omni die", meaning every day. Take the medicine once in 24 hours, ideally at the same time each day. Blood pressure, thyroid and cholesterol medicines are often OD.
Watch out: in eye prescriptions, OD can mean "oculus dexter", the right eye. "Eye drops OD" might mean "right eye", not "once daily". If you see OD on drops, confirm with the pharmacist. Many hospitals now write "once daily" in full to avoid this confusion.
BD (or BID): twice daily
BD comes from "bis die", meaning twice a day. Aim for about 12 hours apart, such as 8 am and 8 pm. Metformin, many antibiotics and some painkillers are often BD.
TDS (or TID): three times daily
TDS comes from "ter die sumendum", meaning to be taken three times a day. Space doses around 8 hours apart while awake, such as 7 am, 3 pm and 11 pm, or with breakfast, lunch and dinner if the medicine goes with food.
QID (or QDS): four times daily
QID means four times a day, about every 6 hours while awake. It is common for some antibiotics and cough syrups.
SOS, HS, AC and PC: the "when" codes
Frequency is half the story. The other half is timing. These prescription abbreviations tell you when to take each dose.
SOS meaning in prescription
The SOS meaning in prescription language is "si opus sit": only if needed. You take an SOS medicine when the symptom appears, such as fever, pain or vomiting, not on a fixed schedule. Doctors often add a maximum, such as "SOS, max 3 per day". PRN ("pro re nata") means the same thing and appears more on hospital charts.
HS meaning in medicine
HS meaning in medicine is "hora somni": at bedtime. Some medicines cause sleepiness, like certain antihistamines. Others work best overnight, like some cholesterol and acidity medicines.
AC PC meaning in prescription
The AC PC meaning in prescription terms is "ante cibum" (before food) and "post cibum" (after food). "Before food" usually means 30–60 minutes before a meal. "Empty stomach" usually means 1 hour before or 2 hours after eating. Many Indian doctors write "BBF" (before breakfast) or "AF" (after food) instead.
STAT and other urgent codes
STAT means immediately, as a single dose. You will see it more often in hospitals and emergency care.
In simple terms: OD is once, BD is twice and TDS is three times a day. SOS means only when you need it, and HS means at bedtime. If a short form could mean two things, ask the pharmacist before you take the medicine. |
Prescription abbreviations chart: the complete cheat sheet
Here is a practical chart covering the OD BD TDS meaning and every other common short form, which you can screenshot or print for the family medicine box.
Short form | Full form (Latin/English) | Meaning | Example clock times |
OD | Omni die | Once a day | 8 am |
BD / BID | Bis die | Twice a day | 8 am, 8 pm |
TDS / TID | Ter die sumendum | Three times a day | 7 am, 3 pm, 11 pm |
QID / QDS | Quater in die | Four times a day | 6 am, 12 pm, 6 pm, 12 am |
HS | Hora somni | At bedtime | 10 pm |
SOS / PRN | Si opus sit / Pro re nata | Only if needed | When symptom appears |
AC | Ante cibum | Before food | 30 min before meals |
PC | Post cibum | After food | Right after meals |
STAT | Statim | Immediately, once | Now |
PO | Per os | By mouth | — |
SL | Sub lingual | Under the tongue | — |
q6h / q8h | Quaque 6/8 hora | Every 6 or 8 hours | Strict clock spacing |
Tab / Cap / Syp | Tablet / Capsule / Syrup | Form of medicine | — |
x 5 days | — | Duration | Take for 5 days |
1-0-1 dosage meaning: the Indian pattern system
Many Indian prescriptions skip Latin and show the OD BD TDS meaning as a number code instead. The 1-0-1 dosage meaning is: one dose in the morning, none in the afternoon, one at night. The three positions stand for morning, afternoon and night.
• 1-0-0: morning only (same as OD in the morning)
• 0-0-1: night only (often written with HS)
• 1-0-1: morning and night (same as BD)
• 1-1-1: morning, afternoon and night (same as TDS)
• ½-0-½: half a tablet morning and night
Some doctors add a fourth digit for bedtime. If you see four numbers, ask what each position means.
Short forms that cause dangerous mix-ups
The Institute for Safe Medication Practices lists some abbreviations as "error-prone". In Indian homes, these cause the most trouble:
• OD on eye or ear drops: once daily, or right eye?
• BD vs TDS in poor handwriting: a 50% dosing difference
• "U" for units (insulin): can be misread as 0 or 4
• Trailing zeros: "5.0 mg" can be read as 50 mg
• Missing leading zeros: ".5 mg" can be read as 5 mg
In 2025, the Punjab and Haryana High Court called legible prescriptions part of the right to health. It directed doctors to write in capital letters until prescriptions are digitised. If you cannot read a line, it is your right to ask.
Where Seht helps
A photo of every prescription, saved by date and doctor, prevents most home mistakes. In the Seht app, you can store each family member's prescriptions next to their reports, so carers and grandparents always see the latest version. When the pharmacist offers a cheaper option, check our guide to generic vs branded medicines in India. To bring the right questions to your next visit, see 10 questions to ask doctor about test results.
When to see a doctor
Contact your doctor or pharmacist promptly if:
You cannot read a medicine name, dose or abbreviation clearly
You took a double dose or mixed up BD and TDS
A child's dose seems different from the label or earlier prescriptions
You develop rash, swelling, breathlessness or severe stomach upset after a new medicine
An SOS medicine is needed more often than the maximum written
An elderly parent is taking several medicines with overlapping timings
If someone has swallowed too much medicine, has trouble breathing, or swelling of the lips or face, call 112 or 108 immediately.
Related reading on Seht
FAQs
What is the OD BD TDS meaning in a prescription?
The OD BD TDS meaning is once a day, twice a day and three times a day. OD comes from "omni die", BD from "bis die" and TDS from "ter die sumendum". BD doses are usually about 12 hours apart, and TDS doses about 8 hours apart while awake. Always follow any specific timing your doctor writes.
What does SOS mean in a prescription?
SOS stands for "si opus sit", meaning only if needed. You take the medicine when the symptom appears, such as fever or pain, rather than at fixed times. Many prescriptions add a limit, like "maximum three times a day". If you need an SOS medicine very often, tell your doctor, because the cause may need treatment.
What does 1-0-1 mean on a prescription?
In the Indian number system, the three positions stand for morning, afternoon and night. So 1-0-1 means one dose in the morning and one at night, with nothing in the afternoon. It is the same as BD. Similarly, 1-1-1 means three times a day and 0-0-1 means only at night.
Is BD the same as every 12 hours?
Mostly, yes. BD means twice a day, and for most medicines, spacing doses about 12 hours apart works best, such as 8 am and 8 pm. Some medicines are linked to meals instead, such as after breakfast and after dinner. If your prescription says "q12h", follow exact 12-hour spacing, which matters for some antibiotics.
What is the difference between AC and PC in medicine?
AC means "ante cibum", or before food, usually 30–60 minutes before a meal. PC means "post cibum", or after food, usually right after eating. Some medicines, like certain acidity tablets, work best before meals. Others, like many painkillers, are taken after food to protect the stomach. Your doctor chooses based on the medicine.
Download Seht — free on iOS and Android
Seht keeps every family member's prescriptions, dated and organised, alongside their reports, so whoever is giving the medicine can check OD, BD or TDS in seconds.
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Sources and references
Institute for Safe Medication Practices (ISMP). List of Error-Prone Abbreviations, Symbols, and Dose Designations. https://www.ismp.org
National Medical Commission. Registered Medical Practitioner (Professional Conduct) Regulations, 2023 — Generic Drugs and Prescription Guidelines. New Delhi: NMC; 2023.
Medical Council of India. Indian Medical Council (Professional Conduct, Etiquette and Ethics) Regulations, 2002, clause 1.5 (as amended in 2016) on legible, generic-name prescribing.
Punjab and Haryana High Court. Order on legible prescriptions as part of the right to health under Article 21 (Justice Jasgurpreet Singh Puri), August–September 2025.
World Health Organization. Medication Without Harm: WHO Global Patient Safety Challenge. Geneva: WHO; 2017.
Disclaimer: This blog is for informational purposes only and is not medical advice. Seht helps families stay informed, but is not a substitute for professional healthcare guidance.
