How do I properly collect a 24-hour urine sample?

How to Properly Collect a 24-Hour Urine Sample

Empty your bladder completely at the start time and discard this urine, then collect every single void for exactly 24 hours, including the final void at the end time. 1

Critical Starting Procedure

• Discard the first void completely - When you begin at your chosen start time, urinate and throw away this urine entirely, then note the exact time 2, 3
• This discarded void represents urine that accumulated in your bladder before the collection period began 2
• All subsequent urine from this point forward must be collected for exactly 24 hours 1, 3

Collection Technique During the 24-Hour Period

• Collect 100% of every void - Every single time you urinate during the 24-hour period, collect all the urine in the provided container 1, 3
• Store the collection container in a cool location or refrigerator between voids 1
• If you accidentally miss even one void or spill urine, the entire collection is invalid and must be restarted 3, 4

Critical Ending Procedure

• Include the final void - At exactly 24 hours after your start time, empty your bladder completely and collect this final urine 1, 2
• This final void must be included in the collection, as it represents urine produced during the 24-hour period 2
• Record the total urine volume accurately before bringing the sample to the laboratory 3

Fluid and Diet Considerations

• Maintain your usual fluid intake based on thirst - Do not artificially increase or restrict your fluid intake during collection, as this should reflect your normal physiological state 2
• Avoid collecting during acute illness, fever, urinary tract infections, or uncontrolled medical conditions, as these transiently alter urine output 1
• If instructed to measure sodium excretion simultaneously, maintain your typical dietary sodium and protein intake 1

Common Pitfalls to Avoid

• Failure to record total volume - This was the single most common error (48.5% of incidents) before standardized instructions were implemented 3
• Using inappropriate containers - Nearly half of patients incorrectly used plastic soft drink bottles instead of proper collection containers 4
• Incomplete collection - Studies show that 50.7% of patients supply inadequate samples, with females nearly 50% less likely to provide adequate collections compared to men 5
• Changing drinking habits - Almost one-third of patients inappropriately altered their fluid intake to "collect more urine," which invalidates the test 4

Verification of Adequate Collection

• The laboratory will verify adequacy by measuring 24-hour creatinine excretion, which should fall within expected ranges based on your body weight 5
• If creatinine excretion is outside reference ranges, the collection may be deemed inadequate and require repeating 3, 5
• A reference change value of >54.5% variation in urine volume between collections suggests incomplete collection 3