Nursing Fundamentals: Intake and Output, Hydration Status, and Daily Weights

Why Intake & Output (I&O) and Daily Weights Matter

Intake and output tracking is more than “charting numbers.” It is a bedside decision-support tool that helps the team detect dehydration, fluid overload, kidney perfusion problems, medication effects (e.g., diuretics), and response to IV fluids or tube feeds. Daily weights are often the most sensitive indicator of overall fluid balance because fluid can shift into tissues (edema) without showing up immediately as measurable output.

Key idea: I&O measures what goes in and what comes out. Daily weights estimate the net result of fluid changes in the body. Use both together to recognize trends early and report them clearly.

Units and quick conversions used in practice

• Most I&O is recorded in mL. (Some facilities use “cc,” which equals mL.)
• 1 kg weight change ≈ 1 liter (1000 mL) fluid change. A 2 kg gain in 24 hours can indicate ~2 L fluid retention.
• Common container volumes: many water pitchers are 1000 mL when full; many cups are 240 mL (8 oz). Always verify your unit’s containers.

What Counts as Intake (and How to Record It)

Oral intake

Record all fluids the patient swallows that are liquid at room temperature or melt to liquid (depending on facility policy). When in doubt, follow your unit’s I&O guidelines and ask the nurse.

• Counts: water, juice, coffee/tea, milk, soda, oral nutrition supplements, broth, gelatin, ice chips (often charted as a fraction of volume; many units count ice chips = 50% of the measured amount because of air space).
• May count depending on policy: popsicles, soups, liquid medications (some units include; many do not unless large volume).
• Do not count: fluids used for mouth care that are not swallowed.

IV fluids (reporting perspective)

Beginners often do not program pumps independently, but you should understand what to observe and report so the RN can chart accurately.

• Continuous IV fluids: intake is the volume infused during the shift. If a pump displays “volume infused,” that number is often used for documentation (per facility policy).
• Intermittent IV medications/flushes: may be included as intake depending on policy and clinical context (e.g., strict I&O). If you are not charting IV intake, still report notable volumes or frequent boluses to the RN.
• What you can do safely: verify the bag label matches the order, note the rate displayed, note the volume remaining/infused, and report discrepancies. Do not silence alarms without addressing cause per policy; do not disconnect tubing.

Enteral tube feeds (as reported)

Tube feeding intake is typically documented by the RN, but you may be asked to measure and report volumes.

Continue in our app.

• Listen to the audio with the screen off.
• Earn a certificate upon completion.
• Over 5000 courses for you to explore!

Or continue reading below...

Download the app

• Continuous feeds: report the rate and the total volume delivered over the time period (pump “volume infused” if available).
• Bolus feeds: report the amount given and the time.
• Flushes: water flushes can be a significant fluid source; report the volume and frequency.
• Residuals: follow facility policy; do not independently aspirate/return unless trained and authorized.

What Counts as Output (and How to Record It)

Urine output

Urine is the most common measurable output and a key indicator of kidney perfusion and hydration status. Accurate measurement requires consistent technique and avoiding double-counting.

• Counts: urine in a hat, urinal, bedside commode collection, Foley catheter drainage bag or urometer, external catheter canister (if used).
• Do not count twice: if urine is measured in a hat and then poured into a toilet, chart only once. If urine is emptied from a Foley bag into a graduate, chart the emptied amount once.

Emesis (vomit)

• Measure when possible: use an emesis basin with volume markings or pour into a graduated container.
• If not measurable: estimate and document as “small/moderate/large” per facility policy, and describe appearance (e.g., coffee-ground, bright red, bilious) and time.

Stool (estimates when applicable)

Stool is not always measured in mL, but it matters clinically, especially with diarrhea, GI bleeding, or ostomies.

• Toilet stool: often charted as occurrence with consistency (formed/loose/watery) rather than volume.
• Liquid stool: may be estimated in mL if collected in a commode hat or bedpan and policy requires strict I&O.
• Ostomy output: can often be measured in mL; empty into a graduate if the pouch is not calibrated.

Drains (when present)

Many patients have surgical drains (e.g., JP), wound vac canisters, or other drainage systems. Output should be measured and recorded per device type and policy.

• JP/Hemovac: measure in mL; note color/character (serosanguinous, sanguineous, purulent).
• Chest tube systems: usually documented by the RN; report changes in amount or appearance promptly.
• NG/OG suction canisters: report volume and appearance; avoid disconnecting unless trained and directed.

Step-by-Step: Measuring Urine Accurately

General principles (apply to all methods)

• Use a calibrated container: a graduated cylinder/collection container with clear mL markings.
• Read at eye level: place on a flat surface and read the meniscus (curved surface) at eye level.
• Time-stamp your measurement: know whether you are recording per void, per shift, or per 24 hours.
• Avoid double-counting: once measured and documented, empty and reset the collection device as appropriate.
• Infection prevention: wear gloves; avoid splashing; clean equipment per policy.

Method A: Hat in toilet/commode

1. Prepare: place the hat securely under the toilet seat or in the bedside commode bucket before the patient voids.
2. After voiding: put on gloves and carefully remove the hat without spilling.
3. Measure: if the hat has clear mL markings and your facility allows, read directly at eye level. If markings are unclear, pour into a graduated container.
4. Document: record the volume in mL and time (or within the correct time block on the flowsheet).
5. Empty and rinse/replace: empty into toilet, rinse if policy allows, and set up for next void to prevent missed output.

Method B: Urinal

1. Before use: verify the urinal is clean and has readable markings.
2. After voiding: keep the urinal upright on a flat surface.
3. Measure: read mL at eye level. If the urinal is not well-calibrated, pour into a graduated container.
4. Document and empty: chart once, then empty and rinse per policy.

Method C: Foley catheter drainage bag (without manipulating sterile connections)

Safety note: Do not disconnect catheter tubing from the drainage bag. Maintain a closed system to reduce infection risk.

1. Identify the correct port: use the drainage spout at the bottom of the bag (not the tubing connection).
2. Position a clean graduate: place it below the bag outlet to allow gravity drainage.
3. Drain: open the spout and allow urine to flow into the graduate. Avoid touching the outlet to the container.
4. Close securely: close the spout to prevent leaks.
5. Measure: read volume at eye level and note urine characteristics (clear, cloudy, bloody, strong odor) for reporting.
6. Document once: record the emptied amount for the time period.

Method D: Urometer (hourly measurement device)

Some Foley setups include a urometer chamber for more precise hourly output.

1. Read the urometer scale: at eye level, using the chamber’s markings.
2. Record at ordered intervals: often hourly in higher-acuity settings.
3. Do not reset or drain without direction: follow unit policy; report low hourly outputs promptly.

Calibrating and Verifying Containers (Preventing Common Errors)

Common accuracy problems

• Unmarked cups or “guestimating”: leads to large errors.
• Ice chip confusion: counting full volume instead of melt volume per policy.
• Multiple containers: patient drinks from water pitcher, coffee cup, and family brings beverages—intake gets missed.
• Double-counting output: measuring in a hat, then later measuring again after pouring into another container.

Practical fixes

• Standardize the patient’s drinkware: use one marked cup/pitcher when possible.
• Mark starting volumes: if a pitcher is filled to 1000 mL, note the starting level and re-check later.
• Label “do not discard” when needed: for emesis or stool that must be assessed/measured.
• Clarify policy for ice chips and supplements: ask once, then apply consistently.

Daily Weights: Technique and Interpretation

Why daily weights are powerful

Fluid can be retained in tissues (edema) or third-spaced, so the patient may gain weight even if measured intake/output seems balanced. Daily weights help detect these hidden shifts.

Step-by-step: obtaining an accurate daily weight

1. Use the same scale: bed scale vs standing scale results are not interchangeable. Stick with one method when trending.
2. Same time each day: ideally early morning.
3. After voiding: reduces variability from bladder volume.
4. Similar clothing/linens: gown only when possible; remove heavy items (shoes, jackets). For bed scales, keep linen/blanket setup consistent.
5. Ensure safety: if standing, use appropriate assistance and mobility aids; if bed scale, ensure the bed is zeroed per manufacturer instructions.
6. Document precisely: record in kg if that is your facility standard; avoid rounding excessively.

Relating weight trends to fluid balance

• Rapid gain: consider fluid retention/overload, especially with edema or lung findings.
• Rapid loss: may reflect diuresis, dehydration, poor intake, or GI losses.
• Compare to I&O: if I&O suggests “net even” but weight rises, suspect unmeasured intake (flushes, hidden fluids) or third spacing; if I&O shows large negative but weight unchanged, suspect measurement gaps or scale inconsistency.

Beginner Cues to Recognize and Report: Dehydration vs Fluid Overload

Possible dehydration / volume depletion cues

• Dry mucous membranes (dry mouth, cracked lips), poor skin turgor (less reliable in older adults)
• Tachycardia or new dizziness/weakness
• Decreasing urine output (fewer voids, smaller volumes, darker urine)
• Concentrated urine or strong odor (not diagnostic alone)
• New confusion or lethargy (especially older adults)

Possible fluid overload cues

• Edema (ankles, sacrum), tight skin, rapid weight gain
• Crackles on lung assessment (report if heard/if patient develops new cough or shortness of breath)
• Increasing work of breathing, orthopnea, decreased oxygen saturation (report per policy)
• Rising blood pressure or bounding pulses (trend-based concern)
• Decreasing urine output can also occur in overload if kidney perfusion is impaired—report the pattern, not just the assumption

When to escalate promptly (examples)

• Urine output markedly decreased from baseline or very low over several hours (follow unit thresholds; commonly <30 mL/hr in adults is concerning depending on context)
• New/worsening shortness of breath, crackles, or rapid weight gain
• Persistent vomiting/diarrhea with poor intake
• Sudden change in mental status with poor intake/output pattern

Case-Based Documentation Exercises

Exercise 1: Complete an I&O flowsheet (day shift example)

Scenario: Adult patient on a medical unit. Strict I&O ordered. You are documenting from 0700–1900.

Your tasks:

• Calculate totals: Total intake = 240 + 237 + 100 + 200 + 180 = 957 mL
• Calculate totals: Total output = 350 + 150 + 200 + 40 + 300 = 1040 mL
• Compute net: Net = Intake - Output = 957 - 1040 = -83 mL
• Identify any documentation clarifications needed (e.g., confirm facility policy for counting ice chips; ensure stool volume estimation is acceptable for strict I&O).

Exercise 2: Identify concerning trends from 24-hour data

Scenario: Over 24 hours, the patient’s I&O shows net -1200 mL. Daily weight increased from 70.0 kg to 71.2 kg.

Questions:

• What mismatch do you see between I&O and weight trend?
• List two possible explanations (measurement gaps, unrecorded intake such as flushes, scale inconsistency, third spacing/edema).
• What focused observations should you check and report? (edema location, lung sounds/crackles, urine output pattern, presence of drains, accuracy of container measurements, whether weight was taken on same scale/time/clothing).

Exercise 3: Communicate changes using SBAR

Scenario: Since 0700, urine output has decreased: 0900 = 200 mL, 1200 = 100 mL, 1500 = 50 mL. Patient reports dry mouth and feels lightheaded when sitting up. Mucous membranes appear dry. Current shift intake is 400 mL.

Write an SBAR message:

S: I’m calling about decreasing urine output and possible dehydration signs in Room ___.  UOP has dropped over the shift and the patient feels lightheaded.  B: Strict I&O is ordered. No Foley; measuring with urinal. Intake so far is 400 mL.  A: Urine outputs: 0900 200 mL, 1200 100 mL, 1500 50 mL. Mucous membranes are dry; patient reports dry mouth and lightheadedness when sitting up.  R: Please assess the patient and consider orders/plan for hydration. Do you want orthostatic vitals, a bladder scan, or repeat urine measurement at a specific time?

Scenario (fluid overload): Patient gained 1.5 kg since yesterday morning, has new ankle edema, and you hear new crackles at the bases during routine care. Urine output is decreasing compared with yesterday.

Write an SBAR message:

S: I’m calling about possible fluid overload—weight is up 1.5 kg since yesterday and there are new crackles and edema.  B: Patient is receiving IV fluids (type/rate per MAR) and has been on strict I&O.  A: Weight increased from __ to __ kg. New bilateral ankle edema. New crackles at lung bases. Urine output is lower than yesterday (provide numbers/time).  R: Please evaluate for fluid overload and advise whether to adjust fluids/diuretics or obtain further assessment (e.g., lung assessment, oxygen needs, labs per provider).