Prescription Writing 101

Prescription writing is something that I used to worry so much about in my 3rd year of medical school. I probably killed a whole tree tearing up prescriptions that were wrong. Why did I worry so much about it? Prescription writing was not covered very well at my medical school. And with the amount of material that needs to be covered in those 4 years, I’m sure writing prescriptions is not that well covered at any medical school. Maybe that’s one of the reasons there are so many medication errors in medicine. Look at some of these commonly quoted statistics:

  • Medication errors occur in approximately 1 in every 5 doses given in hospitals.
  • One error occurs per patient per day.
  • 1.3 million people are injured and approximately 7000 deaths occur each year in the U.S. from medication-related errors
  • Drug-related morbidity and mortality is estimated to cost $177 billion in the U.S.

While these are just estimates from various studies and statistical models, the numbers are staggering. If there are 800,000 physicians in the United States, each physician accounts for $221,250! Do you still wonder why malpractice insurance is so expensive?

Hopefully if you are reading this, you are interested in NOT making mistakes. Even though I don’t think I caused any major harm to any of my patients with prescription errors, I wish that I had read something like this when I first started writing prescriptions when I was in my 3rd year of medical school.


A prescription is an order that is written by you, the physician (or medical student with signature by a physician) to tell the pharmacist what medication you want your patient to take. The basic format of a prescription includes the patient’s name and another patient identifier, usually the date of birth. It also includes the meat of the prescription, which contains the medication and strength, the amount to be taken, the route by which it is to be taken and the frequency. Often times, for “as needed” medications, there is a symptom included for when it is to be taken. The prescriber also writes how much should be given, and how many refills. Once completed with a signature and any other physician identifiers like NPI number or DEA number, the prescription is taken to the pharmacist who interprets what is written and prepares the medication for the patient. Let’s break it down.

Patient Identifiers

According to the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) national patient safety goals, at least two patient identifiers should be used in various clinical situations. While prescription writing is not specifically listed, medication administration is. I think prescription writing should be considered in this category as well. The two most common patient identifiers are full name and date of birth. These are the FIRST things to write on a prescription. This way you don’t write a signed prescription without a patient name on it that accidentally falls out of your white coat and onto the floor in the cafeteria.


This is an easy one. This is the medication you want to prescribe. It generally does not matter if you write the generic or the brand name here, unless you specifically want to prescribe the brand name. Remember, if you do want the brand name, you specifically need to tell the pharmacist – “no generics.” There are several reasons why you would want to do this, but we won’t get into that here. On the prescription pad, there is a small box which can be checked to indicate “brand name only” or “no generics”.


After you write the medication name, you need to tell the pharmacist the desired strength. Many, if not most, medications come in multiple strengths. You need to write which one you want. Often times, the exact strength you want is not available, so the pharmacist will substitute an appropriate alternative for you. For example, if you write prednisone (a corticosteroid) 50 mg, and the pharmacy only carries 10 mg tablets, the pharmacist will dispense the 10 mg tabs and adjust the amount the patient should take by a multiple of 5.


Using my previous example for prednisone, the original prescription was for 50 mg tabs. The prescriber would have written “prednisone 50 mg, one tab….” (I’ll leave out the rest until we get there). The “one tab” is the amount of the specific medication and strength to take. Again using my previous example, the instructions would be rewritten “prednisone 10 mg, five tabs….” You can see that “one tab” was changed to “five”. Pharmacists make these changes all the time, often without any input needed from the physician.


Up until this point, we have been using plain English for the prescriptions. The route is the first opportunity we have to start using English or Latin abbreviations. A NOTE: it is often suggested that to help reduce the number of medication errors, prescription writing should be 100% English, with no Latin abbreviations. I will show you both and let you decide. There are several routes by which a medication can be taken: By Mouth (PO), Per Rectum (PR), Sublingually (SL), Intramuscularly (IM), Intravenously (IV), Subcutaneously (SQ)

As you can see, the abbreviations are either from Latin roots like PO – per os – or just common combination of letters from the English word. Unfortunately when you are in a hurry and scribbling these prescriptions, (there is a truth behind never being able to read a physician’s hand writing) many of these abbreviations can look similar. For example, intranasal is often abbreviated “IN,” which, when you are in a hurry, can be mistaken for “IM” or “IV.” Check this out:

Common Route Abbreviations:

  • PO (by mouth)
  • PR (per rectum)
  • IM (intramuscular)
  • IV (intravenous)
  • ID (intradermal)
  • IN (intranasal)
  • TP (topical)
  • SL (sublingual)
  • BUCC (buccal)
  • IP (intraperitoneal)

The frequency is simply how often you want the prescription to be taken. This can be anywhere from once a day, once a night, twice a day or even once every other week. Many frequencies start with the letter “q.” Q if from the Latin word quaque which means once. So it used to be that if you wanted a medication to be taken once daily, you would write QD, for “once daily” (“d” is from “die,” the Latin word for day). However, to help reduce medication errors, QD and QOD (every other day) are on the JCAHO “do not use” list. Instead you need to write “daily” or “every other day.”

Common Frequencies Abbreviations:

  • daily (no abbreviation)
  • every other day (no abbreviation)
  • BID/b.i.d. (Twice a Day)
  • TID/ (Three Times a Day)
  • QID/q.i.d. (Four Times a Day)
  • QHS (Every Bedtime)
  • Q4h (Every 4 hours)
  • Q4-6h (Every 4 to 6 hours)
  • QWK (Every Week)
The “Why” Portion

Many prescriptions that you write will be for “as needed” medications. This is known as a “PRN” (from the Latin pro re nata, meaning as circumstances may require). For example, you may write for ibuprofen every 4 hours “as needed.” What is commonly missed is the “reason.” Why would it be needed? You need to add this to the prescription. You should write “PRN headache” or “PRN pain” so that the patient knows when to take it.

How Much

The “how much” instruction tells the pharmacist how many pills should be dispensed, or how many bottles, or how many inhalers. This number is typically written after “Disp #.” I highly recommend that you spell out the number after the # sign, though this is not required. For example: I would write “Disp #30 (thirty).” This prevents someone from tampering with the prescription and adding an extra 0 after 30, turning 30 into 300.


The last instruction on the prescription informs the pharmacist how many times the patient will be allowed to use the same exact prescription, i.e. how many refills are allowed. For example, let’s take refills for oral contraceptives for women. A physician may prescribe 1 pack of an oral contraceptive with 11 refills, which would last the patient a full year. This is convenient for both the patient and physician for any medications that will be used long term.

Prescription Writing Examples:
Prescription Writing 101 - Example

This example is a common medication prescribed when people are leaving the hospital. It is one 100 mg tablet, taken at bedtime. The prescription is for 30 pills and no refills.

Prescription Writing 101 - Example 2

Zofran is a very popular anti-nausea medication used after surgery. You’ll notice this script is missing the “amount.” IV medications are a little different in that the amount and strength are kind of mixed together. This is not always the case though. You also see that this is an “as needed” or “PRN” medication. When the patient complains of nausea, the nurse can give this medication because it has been prescribed.

Prescription Writing 101 - Example 3

This example shows a common way to write prescriptions for liquids, especially for children. Obviously “liquid” isn’t the medication, but you get the idea. Liquids come in specific strengths per amount of liquid. Here, the strength is 10 mg per 5 mL. We only want to give 5 mg though, so the “amount” that we prescribe is only 2.5 mL per dose. It’s given by mouth every 4 hours. We are dispensing “1 (one) bottle”. You could also just write “1 (one)” as the pharmacist would know what you meant.

To finish up, here is a list of the JCAHO “Do Not Use” List:

  • U or u (unit) – use “unit”
  • IU (International unit) – use “International Unit”
  • Q.D./QD/q.d./qd – use “daily”
  • Q.O.D./QOD/q.o.d./qod – use “every other day”
  • Trailing zeros (#.0 mg) – use # mg
  • Lack of leading zero (.#) – use 0.# mg
  • MS – use “morphine sulfate” or “magnesium sulfate”
  • MS04 and MgSO4 – use “morphine sulfate” or “magnesium sulfate”

Did we miss an example you are looking for?  Give us a comment below and let us know!

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  • Cat

    Today I have wrote a prescription for lorazepam 0.5 mg following ECT for post ICTAL irritability. The ECT occurs once every 3 weeks.

    I wrote the RX as follows: Lorazepam 0.5 mg po upon return from ECT session 1x every 3 weeks.
    The nursing home director wants me to an add a prn after the order as on holidays, ECT schedules can change to other days. To me if you place a prn after the order it makes it an “as necessary” RX. I want it scheduled following the ECT. How can I write this to allow for varying schedules?

    • Ryan Gray, MD

      Great Question!

      You would write the script for Lorazepam 0.5mg po every ECT prn irritability.

      The “as needed” is for post ictal irritability so thats the prn you would write. The frequency is every ECT.


      • Francisco Mata

        I just want to ask. I am a pharmacist and I had this hot argument with a physician with regards to her prescription writing of Valium 10 mg tablet.

        She prescribed Valium 10 mg tablet 1 tablet at bedtime as needed for insomnia #20. I made a suggestion to revise the signa to 1 tablet every bedtime as needed for insomnia, in order to fill the whole quantity.

        She got mad after correcting her and she said she is a doctor she doesn’t need to be corrected since the signa is already correct..

        I’d love hearing from your answer. Thanks!

  • Cat

    Oops “wrote” ….

  • jnilebarnes

    IF you update this, please include INDICATION EVERY TIME. This is a great check for pharmacists to be sure the drug is appropriate for the indication, to avoid errors. In some states this is actually law (Texas, makes it law, but has a weasel out clause when “knowing the indication is not in the patient’s best interest” A left over from more paternalistic days.

    • Ryan Gray

      @jnilebarnes I like it. I’ll try to find a list of states that do require it and put that as well! Thanks!

  • Individual with Interest

    You might write another article to clarify “dispense as written.”  The article could include brand necessary, generic substitution allowed, and generic DAW (for example: generic by specific manufacturer).  The generic DAW information would include whether it would be more clear to write (BRAND NAME) generic DAW or (GENERIC NAME) DAW and why a generic daw would prevent brand being dispensed when the pharmacy might be able to dispense brand as generic.

  • stephen

    could you do a sample for desmopressin (DDAVP) 10 mcg IN. patient takes 2 times daily (morning and evening) with 3 repeats. it comes in a bottle, does the Rx need to say one bottle? thanks

  • Ginny

    I have a prescription for Percocet 7.5/325, ‘y: 1 tab q 4-6 hrs PRN mod-severe pain #30 Thirty 1 refill
    I was wondering what the “y” indicates? I have been in the medical field many years but this is a new one on me. Thanks

    • Ryan Gray, MD

      Not sure – that’s interesting

  • Lucky

    I was wondering how a prescription for 90 2mg Xanax 1 three times daily would look could you please help me with that?

    • justanMT

      Xanax 2mg one tablet three times daily, #90.

      I’m an MT and type these for a psychiatrist every day.

    • Erik Parsons

      Alprazolam 2mg P.O. T.I.D. P.R.N #90 (most docs put PRN for benzodiazapines [unless for seizures] or pain meds. It means as needed. So there you go that says Xanax 2mg by mouth three times a day as needed dispensed as 90 tablets.) I see a psychiatrist and am on a ton of psych meds. I always read my scripts before I leave. Too many mix ups.

      • DR DAN

        John Doe DOB 1/2/89

        Alprazolam 2mg tablet
        SIG: T PO TID PRN Anxiety
        Refills 0 SIGNATURE OF MD

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  • Tammy

    I write multiple scripts on one script pad, at the end though where is says refills I don’t know how to write refill for all or just put the number 1 down, does that mean all four meds can be refilled or just the last med. written on the list, or do I specify refill 1 for lithium, refill 1 for ambien…. How do you do that correctly. I write using Latin and always and . 0 after the dosage amount. Also if, I’m hurry, as always am I legally allowed to changed the meeting date and put my initials ne t to it or change qhs

  • Rhonda

    When writing a prescription fro quantities what is an appropriate amount to prescribe:
    one arm 360 grams
    entire body 90 grams
    trunk 360 grams
    hands or feet 45 grams

    • Ryan Gray, MD

      Not sure – would need more info

  • Cecily Johnson

    I regularly see physicians write prescriptions as 1/2/60 While I understand this to mean 1 tablet twice a day for 60 days (2 months) is this a recognized/acceptable way of writing a presciption

    • Ryan Gray, MD

      Not that I know of!

  • txgal

    What is the XT number on prescription under the dea lic and npi for?

    • Ryan Gray, MD

      Not sure I’ve seen that before.

  • Heather

    Can you add an example for inhalers?

    • Ryan Gray, MD

      It’s very similar.

      Instead of 1 tab by mouth, you would do 1 puff twice a day. Instead of # of pills, you would usually just do #1 or #3 for how many inhalers you want to give. Great question!

  • S Kennedy

    what does a prescription look like for a topical cream, Acitin or Elimite, 30 g, taken at bedtime…and a spray for the linens, if there is one…

  • Danette

    What is the best way to describe the amount to apply for TP medications? Thin layer, pea sized… nothing seems adequate.

  • Tammy

    what is the “two-line Rx Format”?

    • Tammy

      figured it out. sorry about the lame question….. obviously not my field…..

  • bob

    Can someone help me I’m in a taking classes to be a nurse and I’m having a hard time in my pharmacology class writing prescriptions, if anyone is willing to help please let me know by email or this page
    thank you, no bs

  • nate

    Can you post an example on how to write IV antibiotic? thanks!

  • Jessica

    Can you give an example of how to write for a medication taper, such as with Predisone?

  • JLAllen

    Very good page. It would be good to see some more types of medications in the examples. Ones that would have helped when I was an intern include: insulin (esp the quantity dispensed), diabetic supplies (like BG strips), albuterol, steroid taper (the worst to write), Z-pak (actually the easiest to write), antibiotics (with a finite duration), topical meds, and sublingual nitroglycerin.

    And it might be good to point out that the frequency on PRN medications is typically the most frequent something is allowed. (A frequency of 4-6h makes sense on scheduled meds but not on PRNs).

  • Kris

    Thank you so much for this!! This was extremely helpful!! I started my 3rd year rotations yesterday and when my doc handed me the prescription pad and told me to write a prescription I had no idea what to do. This will be a good start for today! Thanks!

  • New nurse

    What is the correct way,in which to write an Rx prescription for the pain medication Roxicodone 30mg tabs. (#120 ) 2daily as need for pain

  • addy

    how do u write a 3 month script for lortab 260 a month for 3 refills equals 780 total? my uncle is on this but it looks weird the way it is written .it doesnt say 260 just 780! thx