PO Medical Abbreviation: By-Mouth Orders and Common Prescription Shorthand

PO means “by mouth” in medical terms. It comes from the Latin per os. On a medication order, PO identifies the oral route; the dose and timing appear elsewhere in the instructions. The Institute for Safe Medication Practices (ISMP) lists PO, “by mouth” and “orally” as preferred alternatives to writing out per os.

For example, this fictional order excerpt says:

Acetaminophen 325 mg tablets: give 650 mg PO once at 08:00 for headache.

It specifies two 325 mg tablets by mouth, one time at 08:00. “PO” supplies neither the number of tablets nor permission to repeat the dose. The complete case below shows the order, administration and later response separately.

Sources checked November 6, 2026. Pharmacist and registered-nurse review: pending. The adult examples are fictional documentation exercises; their medicine choices and doses belong to those cases.

PO intake, poor PO intake and tolerating PO

PO also appears in notes about eating and drinking:

• PO intake: food and fluids taken by mouth.
• Poor PO intake: eating or drinking less than needed or expected. The phrase describes a concern without identifying its cause.
• Tolerating PO: managing the food or drink tried. Read the surrounding note for what was consumed and whether problems such as nausea or vomiting occurred.

A 2022 clinical review of reduced oral intake describes causes beyond swallowing difficulty, including dry mouth, taste changes, reduced appetite and psychosocial circumstances.

When charting, specify the amount, type of intake, time and source of the information. A fictional example is: “11:00: observed drinking 120 mL water; patient reports no nausea afterward.” Overall nutrition, hydration and swallowing safety still need assessment.

How to read a PO medication order

Read the entire instruction, starting with the medicine and its formulation. A tablet strength describes the amount in one tablet. The ordered dose describes the amount to give. In the opening example, 325 mg is the strength and 650 mg is the dose, so two tablets supply that dose.

Work through these fields when reading an order:

• Medicine and formulation: the named product, such as a tablet, capsule or oral liquid, including any release characteristics.
• Strength or concentration: the amount in each tablet or a stated volume of liquid.
• Dose: the amount prescribed for this administration.
• Route: PO means by mouth; IV, IM and SL have different meanings.
• Timing: a one-time instruction, schedule or specified interval.
• Reason and conditions: the indication, plus any as-needed criteria, limits or other instructions that apply.

Clinical systems also associate the order with a patient, prescriber, date, time and current status. A copied sentence in a note may be old, incomplete or discontinued. Check the active order before using it to guide administration, and resolve a discrepancy with the responsible prescriber or pharmacist.

For patients, the dispensing label and the pharmacist’s explanation should make these directions understandable without decoding abbreviations. If the label and a discharge list disagree, contact the pharmacy or treating team for clarification before the next dose. Have both documents and the medicine container available.

PO, IV, IM and SL: compare the routes

The FDA’s route-of-administration definitions distinguish oral, intravenous, intramuscular and sublingual administration. Route changes require the correct product and instructions; matching a medicine name or dose alone is insufficient.

Code	Route and meaning
PO	Oral: taken by mouth. Follow the product’s directions for swallowing, chewing or preparing it.
IV	Intravenous: delivered into a vein. An oral liquid is not an injectable product.
IM	Intramuscular: delivered into a muscle. The injection route must be specified.
SL	Sublingual: placed under the tongue according to the product instructions. Do not replace SL with PO in a copied order.

Buccal administration is another distinct route: the medicine is directed toward the inside of the cheek. Although oral, sublingual and buccal products all involve the mouth, the prescribed placement and formulation determine how they are used. “Put it in your mouth” loses that information.

An electronic medication list should retain the specified route when information is transferred between systems. A human-readable note and the structured route field should agree. If a route is absent from the source, leave it unresolved and obtain clarification; do not fill in PO because it is common.

Common prescription shorthand beside PO

Prescription abbreviations answer different questions. PO is the route. BID is twice daily. PRN means as needed. These meanings are listed in the University of Connecticut School of Pharmacy’s prescription-typing education guide. Read them together with the medicine and dose.

• PO BID: by mouth, twice daily. The medicine’s actual instructions establish when the doses should be taken. See the BID timing guide for the distinction between a daily frequency and a specified interval.
• PO every 6 hours: by mouth at the stated interval. This still requires the medicine, dose and any other conditions.
• PO PRN: by mouth as needed. This fragment does not identify the reason, dose, minimum interval or maximum permitted amount. The PRN guide works through those details.
• PO once: one administration by mouth. Check the date or time attached to it.

NPO means nothing by mouth and is a separate restriction. It can relate to fasting, swallowing safety or another clinical reason. The treating team must reconcile it with any oral-medication orders and specify medication exceptions or alternatives. University Hospitals Birmingham’s nil-by-mouth medication guidance calls for a clinical decision about omitted or continued medicines, with the decision documented and communicated. Its procedure-specific timings are local instructions, not a schedule to apply to every patient.

Why ISMP recommends PO over per os

ISMP’s 2024 list describes os being mistaken for OS, an abbreviation for the left eye. It recommends PO, “by mouth” or “orally” instead of the Latin phrase.

The list also identifies IN being mistaken for IM or IV, and SC for SL. Write “intranasal” and “subcutaneous,” or use the alternatives in the ISMP list, alongside the organization’s approved terminology.

For a patient-facing label, “by mouth” states the route directly. If an entry is unclear, record the verified clarification and retain the original in the correction history.

When a by-mouth order needs clarification

Difficulty swallowing or a request to crush a tablet

If someone has difficulty swallowing a tablet, ask whether the problem also affects food and drink, and discuss it with the pharmacist or treating clinician. The NHS patient guide to swallowing pills advises getting professional advice before crushing pills, opening capsules or otherwise altering medicines.

Crushing a modified-release tablet can change how quickly the drug is released; enteric-coated tablets have a coating intended to protect the medicine until it reaches the appropriate location. The UK NHS Specialist Pharmacy Service guidance explains why the exact preparation must be checked. A PO order alone does not authorize crushing or switching to a liquid.

Liquid medicines and feeding tubes

With a liquid, distinguish milligrams from milliliters. The concentration links the prescribed amount of medicine to the volume measured. Use the supplied or recommended medicine-measuring device and confirm the markings; MedlinePlus describes liquid-measuring devices and common errors. A kitchen spoon is not a dosing device.

Fictional interpretation exercise: an oral liquid is labelled 100 mg per 5 mL, and the case’s prescribed dose is 200 mg. These numbers illustrate a calculation, not a recommended dose.

1. Find the concentration per milliliter: 100 mg ÷ 5 mL = 20 mg/mL.
2. Calculate the corresponding volume: 200 mg ÷ 20 mg/mL = 10 mL.

Here, 200 mg is the amount of medicine and 10 mL is the volume containing it at that concentration. Confirm the actual bottle concentration and pharmacy directions, and use an appropriate medicine-measuring device marked in mL. A different concentration changes the volume.

Administration through a feeding tube needs its own route and preparation instructions. Record the actual tube route instead of calling the dose PO. Tube type, where it ends, formulation and interactions with feeds can affect the choice. The NHS Specialist Pharmacy Service’s enteral-tube guidance addresses these decisions. A product labelled “oral” is not automatically ready to administer through every tube.

A dose was offered or declined

A dose offered but declined was not administered. Record what happened, including the patient’s stated reason if they give one, and the agreed next action. Preparing a tablet or placing it at the bedside is not evidence that it was swallowed.

For professional documentation, the nursing notes guide explains how to separate observed events from patient reports. “Patient reports taking the tablet at home” and “tablet administered by this nurse” describe different sources of information.

PO-01: from an oral order to the administration record

This fictional adult outpatient case uses the opening order. The record identifies Avery, the prescriber Dr. Chen, and administering nurse Morgan. Patient identifiers, the active order, allergy information and earlier medication use have been checked; Avery reports no earlier acetaminophen use that day, consistent with the available record.

The source facts are:

1. At 07:55 on November 6, Dr. Chen enters and signs: “Acetaminophen 325 mg tablets: give 650 mg PO once at 08:00 for headache.”
2. At 08:00, Avery rates the headache 4/10. Morgan administers two intact 325 mg tablets by mouth and observes them being swallowed.
3. At the case’s agreed 08:40 reassessment, Avery reports headache 2/10 and no new symptoms since the dose. The one-time order contains no repeat-dose authorization.

An administration entry can show the facts without repeating the entire consultation:

The dose was given at 08:00, while the response belongs to 08:40. If the response note is entered later, retain the observation time as well as the system’s entry timestamp. Do not copy a planned reassessment into the record as a completed finding.

In a medical chart, the order, medication administration record and narrative may be separate views. Check that they describe the same medicine, amount, route and event. A signed order establishes what was prescribed; the administration record establishes what was actually given.

PO-02: correct a note about a dose that was not given

In this second fictional case, Rowan has a one-time order for an oral tablet at 09:00. At 09:02, before receiving any medicine, Rowan reports a longstanding difficulty swallowing that tablet size. The nurse does not crush or administer it. The prescriber and pharmacist are contacted at 09:05.

At 09:16, Dr. Chen discontinues the tablet order and accepts responsibility for reviewing an alternative during Rowan’s 09:30 assessment. No replacement order has been entered at the point this note is written. No dose has been administered. These times describe this fictional visit, not a standard response deadline.

A draft says:

“09:00: PO medication given crushed in food. Patient tolerated well. Liquid replacement arranged.”

Identify the unsupported claims before opening the answer. Include the difference between the scheduled time and an actual administration time.

Reveal the source check and corrected note

The draft turns a scheduled dose into an administered dose, invents crushing and tolerance, and treats a planned review as a completed replacement arrangement.

09:02: Rowan reported difficulty swallowing tablets of this size. Scheduled oral tablet not administered; no crushing attempted. Prescriber and pharmacist contacted at 09:05. At 09:16, Dr. Chen discontinued the tablet order and confirmed review of an alternative at the 09:30 assessment. No replacement order entered and no dose administered at time of entry.

The medication record should show the non-administration reason and discontinued order status according to the local system. A later prescription or administration needs a separate entry with its own time. The charting practice guide has further examples of correcting a draft against its source.

Copyable PO order and charting checklist

Use this blank record when reviewing an order or documenting a clarification. Keep the original instructions available and enter only facts that have been checked. It includes separate fields for prescribed treatment, actual administration and follow-up, so a requested change does not become a completed event.

Frequently asked questions

What does PO stand for in medical terms?

PO stands for per os, Latin for by mouth. In medication instructions it identifies the oral route. The medicine, dose and schedule must also be stated.

Do PO, po and p.o. mean different things?

They are commonly used for the same by-mouth route. ISMP’s recommended alternatives include uppercase PO and the plain-language terms “by mouth” and “orally.” Resolve unclear handwriting instead of relying on capitalization alone.

Does PO mean a medicine must be a tablet?

No. An oral medicine can be a tablet, capsule, liquid or another formulation intended for that route. The product and its directions establish how it should be prepared and taken.

Does PO mean take it with food?

No. Food instructions are separate. Check the dispensing label and product directions, or ask the pharmacist whether this medicine should be taken with a meal or on an empty stomach.

Does PO BID mean two tablets at once?

No. PO gives the route and BID gives a frequency of twice daily. The dose tells you how many tablets or how much liquid to take each time.

Is PO PRN a complete instruction?

No. It supplies only the oral route and “as needed.” The medicine, dose, reason for use, interval and applicable limits still need to be clear before administration.

Is PO the same as SL?

No. SL means sublingual, under the tongue. Preserve that route and follow the specific product directions; a sublingual instruction should not be rewritten as an ordinary swallowed dose.

Is a buccal medicine taken by mouth in the same way?

Buccal medicines are directed toward the inside of the cheek. Record “buccal” when that is the prescribed route, and retain the product’s placement instructions.

Can an oral liquid be injected if the dose is the same?

No. A product intended for oral use is not an injection. IV and IM administration require a suitable injectable product and an authorized order specifying the route.

Can PO medicine be given through a feeding tube?

That requires a formulation and tube-route review. The prescriber and pharmacist need to establish suitable instructions for the particular medicine and tube; document the route actually used.

Can I crush a PO tablet?

Ask a pharmacist about the exact product before altering it. Some tablets must remain intact, and even capsules that can be opened may contain granules that must not be crushed.

What if I am NPO but still have oral medicines listed?

Ask the treating team which medicines to take, omit or receive another way. Get explicit instructions for each affected medicine; neither the old medication list nor the abbreviation alone resolves the conflict.

Does PO on a medication list prove the dose was taken?

No. It describes the listed route. An administration entry, a patient’s report of home use and a prescription are different records and should be attributed accordingly.

What should I record when a patient declines an oral dose?

Record that it was not administered, the time, the patient’s stated reason if offered, and any notification or agreed follow-up. Do not mark the dose given simply because it was prepared or offered.

What if the route in a note differs from the dispensing label?

Ask the pharmacist or responsible prescriber to reconcile the discrepancy. Record who confirmed the correct instruction and when, then update the affected records through the approved correction process.