When your doctor hands you a prescription, it may seem unreadable. But knowing what the abbreviations mean is important – and may even save your life in case of an error. Here are some basic abbreviations to know before handing a prescription to a pharmacist.

• ā or ante-before
• alt – alternate
• amp – ampule
• amt – amount
• aq or h20 – water
• bol (bolus) – ball
• c̄ (cum) – with
• daw – dispense as written
• d/c – discontinue or discharge
• hr – hour
• liq – liquid
• Hx – history of
• OTC – over the counter
• p̄ (post) – after
• per – through or by
• q (quaque) – every
• rep – repeats
• Rx – prescription or treatment
• s̅ (sine) – without
• sol (solutio) – solution mixture
• sos (si opus sit) – if necessary
• susp – suspension mixture
• Tx – treatment
• UD or ut. dict. (ut dictum) – as directed
• w – with
• w/o – without
• x – multiplied by
• yo – years old

If a doctor wants you to take the medication in a particular way, that will be indicated in the subscription part of the prescription. It details which bodily route the patient will use for the medication and how the medication should be dispensed. Some examples include:

• AAA – apply to the affected area
• AD (auris dextra) – right ear
• AS (auris sinistra) – left ear
• cap – capsule
• comp – compound
• CD – controlled delivery
• CR – controlled release
• cr or crm – cream
• DR – delayed release
• emuls. – emulsion
• ER – extended-release (or emergency room)
• HS – half strength
• gt (gutta) – drop
• inf – infusion
• IJ or (inj.) – injection
• iv (intravenous) – by vein
• IM – intramuscular
• IN or NAS – intranasal
• IR – immediate release
• MR – modified release
• nebul (nebula) – a spray
• npo (nil per os) – nothing by mouth
• OD (oculus dexter) – right eye
• OS (oculus sinister) – left eye
• OU (oculus uterque) – both eyes
• po (per os) – by mouth
• pr (per rectum) – by rectum
• SR – sustained release
• supp (suppositorium) – suppository
• syr (syrupus) – syrup
• tab (tabella) – tablet
• top (topical) – by skin
• TR – timed release
• ung (unguentum) – ointment
• vag – vaginally

One important detail to know is how often you need to take your prescription. You also need to know whether your prescription should be taken with food, with water, or by itself. Read these common abbreviations for how and how often a patient should take their medication.

• ac (ante cibum) – before meals
• achs (ante cibum et hora somni) – before meals and at bedtime
• ad lib (ad libitum) as you desire or need
• alt. h. (alternis horis) – every other hour
• ap (ante prandium) – before a meal
• atc – around the clock
• bid (bis in die) – twice a day
• cc (cum cibos) – with food
• dieb. alt. (diebus alternis) – every other day
• hs (hora somni) – at bedtime
• n or noct (nocte) – during the night
• noct. maneq. (nocte maneque) – at night and in the morning
• pc (post cibum) – after meals
• prn (pro re nata) – as needed
• qam (quaque ante meridiem) – every morning
• qd (quaque die) – once a day
• qid (quater in die) – four times a day
• qh (quaque hora) – hourly
• q.2h. – every 2 hours
• q.3h. – every 3 hours
• q.4h. – every 4 hours
• qn (quaque nocte) – every night
• qs (quantum satis) – as much as needed
• t.i.d. (ter in die) – 3 times a day

Knowing the potential side effects of medication is important for patients. It can help them decide whether the benefits of taking the medication outweigh the risks. The following codes are used as a warning about side effects, especially for people with certain medical conditions that may be affected by the medication.

• ASA – contains acetylsalicylic acid (aspirin)
• C – caution
• D – drowsiness
• G – glaucoma
• H – habit-forming
• I – interaction
• N/V or N&V – nausea and vomiting
• S – diabetes
• X SOS – contains a substance that could cause problems

A prescription contains handwritten instructions for the dispensing and administering of medications. It can be more than an order for drugs, as it can also include instructions for a therapist, the patient, nurse, caretaker, pharmacist or a lab technician for orders for lab tests, X-rays, and other assessments.

Prescriptions have five main sections:

• Superscription – This heading includes the date and the patient’s name, address, age, and other important information.
• Symbol Rx – It’s the universal symbol for “prescription.”

• Inscription – This is the information about the medication itself. It has the name of the ingredients and the amount needed. It includes the main ingredient, anything that helps in the action of the drug, something to modify the effects of the main drug, and the vehicle which makes the medicine more pleasant to take.

• Subscription – The subscription section tells the pharmacist how to dispense the drug. This will have instructions on compounding the drug and the amount needed.

• Signature – The signature has the directions that are to be printed on the medicine. The word sig means “write-on label.”