Nursing care
Intake and Output: the method, the errors, and the exam
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Intake and output tracking records every fluid a patient takes in and every fluid that leaves the body, and it is accurate only when nothing is omitted. Ice chips count as half their volume, not the full amount, and a chart is usually wrong not because of a calculation error but because something was never recorded at all.
Why this skill decides answers
Intake and output, charted as I&O, is one of the few nursing measurements that turns directly into a clinical decision within hours. A negative fluid balance after diuretic therapy confirms the drug is working; a positive balance in a patient with heart failure or renal impairment signals fluid retention before it shows up as crackles or oedema. Because the numbers drive real decisions, whoever charts them has to treat every entry as clinically meaningful, not as paperwork completed after the fact.
This is also why I&O appears constantly on the NCLEX: it is a skill that exposes whether a candidate understands fluid balance as a whole, rather than memorising a definition. A question that asks you to total a shift's intake, or to identify what was left off a chart, is testing the same clinical reasoning a nurse uses at the bedside to decide whether to call a provider about a patient who has not voided in eight hours.
How to do it reliably
Record intake at the time it happens, not from memory at the end of the shift. Every oral fluid counts: water, juice, soup, gelatin once it has melted, and ice chips, which are recorded at half their measured volume because a cup of ice contains roughly half that volume in water once melted. Intravenous fluids, including piggyback medications and flushes, count as intake and are usually the largest and easiest-to-miss contributor if the nurse assumes the pump total is being tracked automatically.
Output includes urine, emesis, diarrhoea, wound drainage, chest tube output, nasogastric drainage, and blood loss estimated from dressings or surgical counts. Use a graduated container for urine rather than estimating, and weigh dressings or count pads for output that cannot be measured directly, converting weight to volume using the standard 1 gram equals 1 millilitre approximation for blood and serous fluid. Total both columns at the end of each shift and at 24 hours, and compare the balance against the patient's trend, not just the day's figure in isolation.
The common errors
The most frequent error is not a wrong number but a missing one. Ice chips melted at the bedside and never entered, a small volume of water used to take medication, or wound drainage absorbed into a dressing without being weighed, all disappear from the chart without anyone noticing, because nothing looks wrong until the total is compared against the patient's clinical picture. Because ice chips are counted at half volume, forgetting to halve the figure, or forgetting to record them at all, both distort the intake total in opposite but equally misleading directions.
IV fluids are another common gap, particularly when a bag is changed mid-shift or a patient receives several small-volume IV piggyback medications that are each easy to treat as too minor to log. Output is under-recorded when a patient voids in the bathroom rather than a hat or urinal and the volume is estimated rather than measured, or when incontinence episodes are not quantified at all. A chart with a suspiciously balanced or perfectly round total for several shifts running is a signal that entries are being estimated rather than measured.
Drills that build it
Practise converting common containers to millilitres until it is automatic: a standard hospital water cup, a soup bowl, an ice chip cup, a juice carton. Run through a mock shift on paper, listing every item a patient consumed or lost and building the running total by hand rather than relying on a calculator, since the exam tests recognition of what counts, not arithmetic speed.
Practise identifying omissions specifically. Take a completed I&O scenario and ask what is missing rather than what is wrong: a patient who received IV antibiotics, ate a full breakfast, and had one voiding recorded, but nothing charted for the ice water at the bedside or the emesis basin used once, is a realistic and testable scenario. This trains the habit of scanning a chart for gaps, which is the more common real-world failure than a miscalculated total.
Exam application
NCLEX questions on I&O typically take one of two forms: a calculation question asking for a total intake, output, or net balance from a list of entries, or a clinical judgement question asking what to do with an imbalance once it is identified. For the calculation form, work through every line item methodically, converting ice chips to half volume and confirming units match, since mixing millilitres and ounces without converting is a common trap.
For the judgement form, connect the imbalance to a cause and a nursing action rather than stopping at the number. A patient with output significantly below intake over eight hours needs assessment for urinary retention or renal impairment before anything else, and the correct answer usually involves assessment and escalation rather than an isolated intervention like forcing fluids. Read the scenario for context clues, recent surgery, diuretic therapy, fever, that explain why the balance looks the way it does.
Quick reference
Intake: oral fluids, ice chips at half their measured volume, IV fluids and flushes, tube feeds, and any liquid medication vehicle. Output: urine, emesis, liquid stool, wound and drain output, nasogastric output, and blood loss, with 1 gram of dressing weight approximated as 1 millilitre of fluid.
Chart at the time of the event, use graduated containers rather than estimates, and total every shift against the patient's running trend rather than in isolation. If a number on the chart cannot be traced to a specific measured event, treat it as unreliable rather than accepting it at face value.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our renal and genitourinary practice questions are the closest set to what this page covers.
Common questions
Do ice chips count as full intake volume?
No. Ice chips are recorded at half their measured volume, because a given volume of ice yields roughly half that volume once melted. Recording the full measured amount overstates the patient's actual fluid intake.
What is the most common mistake in intake and output charting?
Omission, not miscalculation. Small volumes like water taken with medication, melted ice chips, or drainage absorbed into a dressing are frequently never recorded at all, which skews the total more than an arithmetic error would.
How do you convert dressing weight to output volume?
Use the standard approximation that 1 gram of added dressing weight equals 1 millilitre of fluid. Weigh the dry dressing beforehand if possible, weigh it again once saturated, and record the difference as output.
What should a nurse do if output is much lower than intake over several hours?
Assess the patient for urinary retention, check for a distended bladder, and review recent renal function and vital signs before escalating to the provider. The nursing action is assessment first, not an isolated fix like increasing fluids.