The PO medical abbreviation means by mouth: a medicine, food or fluid marked PO is swallowed. It comes from the Latin per os, "through the mouth," and appears as PO, po or p.o. on prescriptions, hospital orders and nursing notes.
PO is a route, meaning it tells you how the medicine enters the body. Alternatives include IV into a vein, IM into a muscle and SL under the tongue. PO is also half of a very common pair, NPO, nothing by mouth. Below, you will see PO in real lines, learn how the oral route differs from the others and find the extra meanings PO picks up in nursing notes.
At a glance
Stands for
By mouth, orallyLatin origin
Per os, through the mouthWritten as
PO, po, p.o.Kind of term
Route of administrationOpposite
NPO, nothing by mouthDo not confuse with
SL (under the tongue) and buccal (inside the cheek), which are not swallowedWhere you see it
Prescriptions, hospital orders, diet orders, intake records
What the PO medical abbreviation means in an order
A medication order has a fixed pattern: drug, dose, route, frequency. PO fills the route slot. "Ondansetron 4 mg PO q8h PRN nausea" says to give the tablet by mouth no more often than every 8 hours when nausea occurs. On a pharmacy label the same idea becomes "take by mouth," because PO is a pharmacy abbreviation that technicians convert into plain words.
PO covers tablets, capsules, liquids, chewables and powders mixed into fluid, as long as the medicine is swallowed. A dissolving tablet placed on the tongue and then swallowed with saliva is usually still written PO, though some orders name it more precisely.
PO in common orders
| As written | Plain wording |
|---|---|
| Metformin 500 mg PO BID | By mouth twice a day |
| Atorvastatin 20 mg PO QHS | By mouth every night at bedtime |
| Ibuprofen 400 mg PO q6h PRN pain | By mouth up to every 6 hours if needed for pain |
| Advance diet as tolerated, encourage PO fluids | Increase food and drink by mouth as the patient can manage |
The last line shows that PO is not only for medicines. Diet and fluid orders use it as well. These lines illustrate format only.
PO intake, PO trial and other nursing uses
As a nursing abbreviation, PO often stands for everything a patient eats and drinks. "Poor PO intake" means the person is not eating or drinking much. "Tolerating PO" means they can keep food and fluids down. A "PO challenge" or "PO trial" after surgery or illness checks whether someone can drink without vomiting before an IV is removed.
Progress note: "Pt tolerating PO, IV fluids stopped, switched antibiotics IV to PO." Here PO appears twice: first for food and drink, then as the route for the new antibiotic tablets.
The switch from IV to PO is a routine step before discharge for many patients, once they can swallow and absorb medicines normally.
By mouth compared with other routes
The route changes how fast a medicine works and how much reaches the blood, so it matters which one is written.
| Abbreviation | Route |
|---|---|
| PO | By mouth, swallowed |
| SL | Under the tongue, dissolved, not swallowed whole |
| PR | Into the rectum |
| IV | Into a vein |
| IM | Into a muscle |
| NG or per tube | Through a feeding tube |
Oral medicines pass through the stomach and liver before reaching the rest of the body, which is why an IV dose and a PO dose of the same drug can differ.
NPO and the Latin root
The os in per os means mouth, the same root found in oral. Add nil, nothing, and you get nil per os, the source of NPO. NPO orders appear before surgery, some procedures and when swallowing is unsafe.
Do not mix this up with OS, the older eye abbreviation for left eye. Same letters, different Latin word. In the prescription and dosing section you can compare these lookalike terms.
Safety notes for the oral route
No official ban applies to PO. The safety questions are practical: can the person swallow safely, can the tablet be crushed, and should it be taken with or without food? Some long acting tablets must never be crushed or chewed because that releases the whole dose at once.
Nurses check swallowing before giving PO medicines to patients after a stroke or with certain conditions. If a patient is NPO, PO medicines are held or changed to another route unless the prescriber says otherwise.
This is a plain explanation of a route abbreviation. If you have trouble swallowing a medicine or want to know whether it can be crushed, ask your pharmacist before changing how you take it.
Frequently asked questions
What does PO mean on a prescription?
PO means by mouth. The medicine is meant to be swallowed, and pharmacy labels usually print take by mouth.
What is the medical abbreviation for by mouth?
The abbreviation is PO, also written po or p.o., from the Latin per os.
What does PO intake mean in a hospital note?
It refers to what the patient eats and drinks by mouth. Poor PO intake means the person is taking in little food or fluid.
What is the difference between PO and NPO?
PO means by mouth, while NPO means nothing by mouth. NPO is often ordered before surgery or when swallowing is not safe.
What does PO daily mean?
PO daily means by mouth once a day. Older orders may show PO QD, but daily is now the safer way to write it.