Prescription Writing (Latin Terms)

Category: Uncategorized.

This series has been presented in a webinar as well. 
Please go here to watch it: Drbeen Webinars


As much as I am not a fan of Latin terms for prescription writing, I understand that following holds true:

  • These are globally taught terms. This allows almost a universal understanding and administration of a prescriptions.
  • Our books, software, infrastructure, processes, and other existing systems already use these terms.

Clearly learning important terms and using them effectively is important for anyone who is part of the chain of drug administration (see first article in this series.)


In this article we will learn following categories of terms:

  • Count/quantity of drug
  • Administration
  • Formulation
  • Frequency


Count of a drug for example, 2 tablets at one time, or 2 capsules at one time, etc. were written originally as roman numerals. For example i for 1, ii for 2, and iii for 3. This then changed into T (which can be thought of the capital roman letter I) with a dot on it.

T with a dot


For example to prescribe Amoxicillin 250 mg tablets, taken 2 tablets orally three times a day for 7 days you will write (note the T with dots in red):

amoxicillin 250 mg two tablets 3 times a day for 7 days

You can write the Ts or ii. Don’t, however, put one T with two dots on it. It is error prone.

So what are some examples of the count/quantity?

  • ii tablets (two tablets)
  • i capsule or i cap (1 capsule)
  • 4 mL (suspension). See notes about the suspension below.

Suspension Administration

Administering table/tea spoons is error prone due to spilling and inaccuracy in filling. Putting quantity in measurable units is preferred. However, for the patient there has to be a way to measure this exact quantity and use. Syringes can be used. Problem with the syringes is the availability, and more importantly choking hazard by the syringe cap for small children.

My opinion is that metric units can be used where the administration is in expert staff’s hand. For a patient table spoon and tea spoon are still the most easy method for compliance.

Route of Administration

A drug can be administered by many routes or exactly only one route depending upon its chemical formulation and the intent of administration. Common routes of administration and their terms are following:

  • p.o. (per os) mouth
  • p.r. (per rectum)
  • SubQ (subcutaneous)
  • IV (intravenous)
  • IM (intramuscular)
  • IN (intranasal)
  • IT (intrathecal)
  • SL (sublingual)
  • Vag (vaginally)

In the Amoxicillin example above the p.o. is for oral administration.


There can be various formulations of the same drug. This is to allow administration of a drug to patients of various ages and state of health. Scope of a drug’s distribution also dictates the formulation. Some common formulations are following:

  • Tab (tablet)
  • Cap. (capsule)
  • Bolus (discrete amount)
  • Susp. (suspension)
  • Syr. (syrup)
  • fl. (fluid)
  • Cr. (cream)
  • Ung. (unguentum) ointment

In the Amoxicillin example above we used tablets, we could have used tab as well with the same clarity.

Frequency of Administration

Writing frequency is possibly the most commonly bothersome area. My approach is to teach the terms that make up the frequency. For example cibum in Latin is for meal, and anti is for before. So anything before meal will be said to be anti cibum and written as a.c.

Here are some terms for Frequency to keep in mind

  • Cibum: meal
    • a.c. (ante-cibum) before meal.
    • p.c. (post cibum) after meal.
  • Meridian (noon)
    • a.m. (ante meridian) in the morning.
    • p.m. (post meridian) in the evening.
  • Die: day
  • Hora: hour
  • Somni: sleep
  • Quque: every
    • qh: every hour
  • Sumendus (take)
  • p.r.n. (pro re nata) as needed

Frequency involving Days

  • o.d. (once a day). Note: this should be replaced with the word daily.
  • q.d. a.m. (quaque die ante meridien) every day after morning
  • b.i.d. (bis in die) two in a day. bds (bis die sumendus. Two in a day take).
  • t.i.d. (ter in die) three in a day. tds (tre die sumendus. Three in a day take)
  • q.i.d. (quarter in die) four in a day. qds (quarter die sumendus. Four in a day take.)
  • q.a.d. (quaque altera die) every alternate day
  • (bis in 7 d) every 7 days. Weekly.

Frequency involving Hours

  • q.i.d. a.m. a.c. (quque in diem ante meridien ante cibum). Once daily before meal. Again the preferred writing method will be to once daily before meal.
  • q.i.d. p.c. (once daily after meal). See above point.
  • h.s. (hora somni) at sleeping time.
  • hor. alt (hora alternis) every other hour.
  • q.h. (every hour).
  • q.1.h. (every hour) q1h.
  • q.2.h. (every two hour) q2h.

Hope these terms provide enough data to help you write prescriptions.



This article series has not covered the following:

  • How to prescribe injections/infusions?
  • How to prescribe Insulin/Steroids?
  • How to perform dosage calculation?

Let me know if you will like me to write about these as well?

When I get a chance I will add some example prescriptions.


Leave a Reply