The UOP medical abbreviation means urine output, the amount of urine a person produces over a stated period, usually recorded in milliliters per hour or per shift. Nurses track it closely in hospitals because it is one of the simplest signs of how well the kidneys and circulation are working.
You will see it on intake and output records, in ICU flowsheets and in progress notes, usually paired with a figure, for example UOP 30 mL/hr. Below is how output is measured, what the numbers in a note mean, and the related shorthand such as I and O that surrounds it.
At a glance
Stands for
Urine outputUnits
Milliliters (mL) per hour, per shift or per 24 hoursCommon adult guide
Often at least about 0.5 mL per kg of body weight per hourWhere you see it
Intake and output records, ICU flowsheets, surgical notesLow output term
Oliguria; no output is anuriaRelated terms
What the UOP medical abbreviation measures
Urine output is simply how much urine comes out. The kidneys filter blood all day, and when blood flow, hydration and kidney function are adequate, a steady stream of urine results. When any of those falter, output often drops before blood tests change, which makes UOP an early warning sign.
For that reason, output is charted for patients after surgery, people with infections such as sepsis, people with heart or kidney disease, and anyone getting IV fluids or medicines that affect fluid balance, such as furosemide.
How nurses measure urine output
- Indwelling catheter. Urine drains into a bag with marked volumes. In intensive care a meter attached to the bag allows hourly readings.
- Collection hat or urinal. A plastic container placed in the toilet or a handheld urinal lets staff measure each void.
- Weighing diapers or pads. In infants and some adults, the dry weight is subtracted from the wet weight. One gram is treated as about one milliliter.
- Bladder scan. An ultrasound check shows how much urine is sitting in the bladder, useful when output seems low.
Each measurement is added to the intake and output record, often called I and O, so the team can compare fluids in with fluids out.
Reading UOP numbers in a note
| Entry | Meaning |
|---|---|
| UOP 45 mL/hr | 45 milliliters of urine per hour |
| UOP 350 mL this shift | Total urine over the shift, often 8 or 12 hours |
| I/O: 2.1 L / 1.6 L | 2.1 liters in, 1.6 liters out over 24 hours |
| UOP down, 15 mL/hr x 2 hrs, MD notified | Output has fallen and the doctor has been told |
ICU handoff: "UOP has been 20 to 25 mL an hour since midnight, team aware, fluid bolus given at 0400." The nurse is flagging lower than expected output and the response the team chose.
What counts as low urine output
A widely used rule of thumb for adults is at least about 0.5 mL per kilogram of body weight per hour, which for a 70 kg adult is about 35 mL an hour. Output below that for several hours is one of the criteria used to define acute kidney injury. Low output over a day, often cited as under about 400 mL in adults, is called oliguria, and almost no urine is anuria.
Children have their own targets based on weight. Hospitals and care teams set their own thresholds and alert rules, so the numbers in any one chart reflect local practice and the person's condition.
Why output changes and what teams check
Low output can come from dehydration, blood loss, low blood pressure, a blocked catheter, an enlarged prostate blocking flow, or kidney damage. High output can follow diuretic medicines, high blood sugar or recovery from some kidney injuries. Nurses usually check the simple things first: is the catheter kinked, is the bag draining, is the bladder full on scan.
Doctors then look at blood pressure, lab results such as BUN and creatinine, and fluid balance before deciding what to do.
UOP charting for students
Record the volume, the time period and the method, and describe the urine's color and clarity. Report changes promptly rather than waiting for the end of the shift. Many units also expect a running 24 hour total.
More flowsheet and handoff terms are listed on the nursing abbreviations hub.
Urine output targets depend on age, weight and health. Anyone worried about how much they or a family member is urinating should speak with a doctor or nurse.
Frequently asked questions
What does UOP mean in nursing?
UOP means urine output. Nurses measure it in milliliters and chart it per hour, per shift or per day.
What is a normal urine output per hour?
A common adult guide is at least about 0.5 mL per kilogram per hour. Targets vary by age and condition, and each hospital sets its own alert levels.
Is UOP the same as I and O?
No. UOP is one part of I and O, intake and output. I and O also counts fluids taken in by mouth, IV and tube feeding.
Why is my family member's urine being measured?
Measuring output helps the team judge hydration, blood flow and kidney function. It is routine after surgery and in many hospital stays. The nurse can explain the reason for a specific patient.