Prescription Abbreviations Explained

Learn what all the confusing abbreviations and short forms on prescriptions mean so you understand exactly how to take your medicines.

Indian doctor prescriptions are filled with Latin abbreviations and medical shorthand. Most people do not know what these mean. You see "T.D.S." on a bottle and do not know if it means once, twice, or three times daily. You see "A.C." and wonder: after food? Before food? You see "O.D." and guess at the meaning.

These abbreviations matter. Taking medicine at wrong frequency or with/without food changes how well it works.

Common abbreviations for frequency (how many times per day)

O.D. or OD = Once Daily

Meaning: One time per day
Example: "Levothyroxine 50mcg O.D." = take 1 tablet once per day
Best time: Usually morning, often on empty stomach

B.D. or BD = Twice Daily

Meaning: Two times per day
Example: "Lisinopril 10mg B.D." = take 1 tablet twice per day
Typical timing: Morning and evening (approximately 12 hours apart)

T.D.S. or TDS = Thrice Daily

Meaning: Three times per day
Example: "Amoxicillin 500mg T.D.S." = take 1 tablet three times per day
Typical timing: Morning, afternoon, evening (approximately 8 hours apart)

Q.I.D. or QID = Four Times Daily

Meaning: Four times per day
Example: "Antacid T.I.D./Q.I.D." = take 3-4 times per day
Typical timing: Before meals and bedtime

Q.H. or QH = Every Hour

Meaning: Every hour (rare, usually for urgent situations)
Example: "Pain medicine Q.H." = take every hour as needed
Use: Usually temporary, not long-term

Q.4H. = Every 4 Hours

Meaning: Every 4 hours (usually not exceeding 6 times per day)
Example: "Cough syrup Q.4H. as needed"
Use: "As needed" medicines, usually temporary

Q.6H. = Every 6 Hours

Meaning: Four times per day at regular 6-hour intervals
Example: "Antibiotic Q.6H." = 12:00 AM, 6:00 AM, 12:00 PM, 6:00 PM
Use: Typically for antibiotics requiring consistent levels

S.O.S. or PRN = As Needed, When Required

Meaning: Only take when you need it (not regularly)
Example: "Pain tablet S.O.S." = take only when pain develops
Use: For occasional symptoms, not routine

H.S. = At Bedtime

Meaning: At night before sleeping
Example: "Sleeping tablet H.S."
Note: "H.S." stands for "hora somni" (hour of sleep in Latin)

STAT = Immediately, Right Now

Meaning: Take immediately without delay
Example: "Pain medication STAT" = take this tablet right now
Use: Emergency situations only

Common abbreviations for timing relative to food

A.C. = Before Food

Meaning: Take on empty stomach, 1 hour before eating
Example: "Take A.C." = eat breakfast at 9:00 AM, take medicine at 8:00 AM
Why important: Food reduces absorption of some medicines

P.C. = After Food

Meaning: Take after eating
Example: "Iron supplement P.C." = take after lunch
Why important: Food may reduce side effects or help absorption

With Meals = With Food

Meaning: Take during a meal
Example: "Ibuprofen with meals"
Why important: Food protects stomach from irritation

Empty Stomach = No food

Meaning: At least 1-2 hours before or after eating
Example: "Levothyroxine on empty stomach"

Abbreviations for medicine dose and quantity

T. or Tablets = Tablet

Meaning: Solid pill form
Example: "T. means 1 tablet"

Cap. = Capsule

Meaning: Capsule form (softer, usually powder inside)
Example: "Cap. Doxycycline 100mg"

ML = Milliliters

Meaning: For liquid medicines
Example: "Cough syrup 5 mL three times daily"

GM = Gram

Meaning: Weight measure for some medicines
Example: "Powder 1 GM"

MG = Milligram

Meaning: Weight measure for tablets
Example: "Aspirin 500 mg"

MCG = Microgram

Meaning: Very small weight measure (1/1000 of milligram)
Example: "Vitamin B12 1000 mcg"

IU = International Units

Meaning: Standard unit for vitamins and hormones
Example: "Vitamin D 1000 IU"

Abbreviations for body system or route

I.M. = Intramuscular (injection into muscle)

Meaning: Injection given into the muscle (usually in arm or buttock)

I.V. = Intravenous (injection into vein)

Meaning: Injection given directly into vein (in hospital usually)

S.C. = Subcutaneous (injection under skin)

Meaning: Injection given under the skin (like insulin injection)

P.O. = Per Oral (by mouth)

Meaning: Take by mouth (swallow tablet or liquid)
Most common: This is the usual route for home medicines

Inhalation = Breathe in

Meaning: Use asthma inhaler or nebulizer

Topical = On the skin

Meaning: Apply cream or ointment to skin surface
Example: "Antibiotic ointment topical"

Real example: Reading a complete prescription

Doctor's prescription reads:

1. Aspirin 75 mg T. O.D. A.C.
2. Lisinopril 10 mg T. B.D. P.C.
3. Vitamin B12 1000 mcg I.M. weekly ×4 weeks
4. Cough syrup 5 mL T.D.S. P.C.
5. Pain tablet 500 mg S.O.S.

Decoded:

1. Aspirin 75 mg tablet: One time daily, before food
   → Take 1 aspirin tablet once per day in morning, on empty stomach

2. Lisinopril 10 mg tablet: Twice daily, after food
   → Take 1 lisinopril tablet two times per day (morning and evening), after eating

3. Vitamin B12 1000 mcg injection: Intramuscular, weekly for 4 weeks
   → Get B12 injection once per week for 4 weeks (go to clinic for injections)

4. Cough syrup 5 mL three times daily, after food
   → Take 5 mL of cough syrup three times per day (morning, afternoon, evening), after meals

5. Pain tablet 500 mg: As needed
   → Take 1 pain tablet only when pain develops (not routine)

Common confusing abbreviations

"OD" confusion

In India: O.D. usually means "Once Daily"
In some countries: O.D. can be confused with "Right Eye"
Safer: Write "Once daily" instead of "O.D." to avoid confusion

"mane" vs "nocte"

Mane = in the morning
Nocte = at night
Example: "Tablet mane" = take in morning
Example: "Tablet nocte" = take at night

"nocte + mane"

Meaning: Take one in morning AND one at night (=twice daily, but using old Latin terminology)

"alt. die" or "alternate days"

Meaning: Take every other day (day 1 yes, day 2 no, day 3 yes, etc)
Example: "Oral iron alt. die" = take day 1, skip day 2, take day 3, etc

"sos" vs "prn" (both mean "as needed")

SOS (Latin: Si Opus Sit) = if necessary
PRN (Latin: Pro Re Nata) = as circumstances arise
Both mean: Take only when symptom develops

What if abbreviation is unclear?

If you see abbreviation you do not understand:

Ask pharmacist: "What does this mean?"
Ask doctor: "How many times should I take this?"
Call clinic: "Can you clarify this abbreviation?"

Do NOT guess. Guessing at "once daily" vs "three times daily" completely changes treatment.

Recording abbreviations properly in your medicine list

When creating your own medicine list, avoid confusion by WRITING OUT full words:

Not clear:

Lisinopril 10mg T.D.S.
Aspirin 75mg O.D.

Clear:

Lisinopril 10 mg: Three times daily, after food (morning, noon, evening)
Aspirin 75 mg: Once daily in morning, on empty stomach

This way, even if you forget abbreviations, the full information is there.

FAQ

What does "Tab 1-2" mean?

Take 1-2 tablets. Usually means if pain mild take 1, if severe take 2.

What if prescription says "Twice a day" instead of "B.D."?

Same meaning. "Twice a day" = twice daily = B.D. = 2 times per day.

Can I take "three times daily" at any times of day?

Ideally evenly spaced (approximately 8 hours apart). But some flexibility OK. Main is to take 3 times rather than exact timing.

What if I missed the exact timing by 30 minutes?

Usually no problem. Take the dose when you remember. Do not double next dose.

Is "bedtime" medicine required at exactly 10 PM?

Flexible. Anywhere from 8-11 PM fine. Key is to take at night, 30 minutes before sleep.

What if label says "Take one twice daily"? How much?

Means 1 tablet, twice per day. Total = 2 tablets per day (morning and evening).