24-Hour Urine Sample
A 24-hour urine sample is simply a collection of all urine passed over a 24-hour period of time.
Before Starting a urine collection:
- Read and follow any instructions given to you by your GP or laboratory.
- Speak to your doctor or laboratory if you have any questions
- There may be certain foods you need to avoid before and during the collection period for some tests
- There may be certain medications you need to avoid before and during the collection period, if so, your doctor should have discussed this with you. Don’t stop taking your medication if you have not discussed this with your doctor. Your doctor may prefer to keep you on the medication but interpret the results in light of your medication intake.
- It is usually best to drink your usual volume of water or other beverages (there is normally no need to drink more or less than usual) - if you know you drink and urinate a lot, you may want to ask for an extra collection container.
- You may wish to use a clean, disposable tub with a wide lid to urinate into and then transfer this to the collection bottle provided
- Plan when you do the collection:
i. It is usually best to start your collection in the morning so you can take the sample to the GP or lab the next day when it is fresh
ii. you may find it easiest to do this on a day when you can stay at home. However, you may be best to avoid collection on a Friday or Saturday if the GP/ laboratory opening hours mean you cannot take your sample to the lab soon after the collection on Saturday or Sunday
i. For some tests, there may be a known volume of acid in the bottom of the collection container in order to preserve certain substances in the urine that the laboratory will measure
ii. Follow any specific instruction given with these collection bottles e.g. do not rinse out or touch the acid
iii. Follow any instructions given in case of spillage of the acid.
How to do a 24-hour urine collection
Note - sometimes, you may be asked to do a shorter or longer collection period, the instructions are just the same as below, only the collection time is changed.
1. Check that your name and other requested details are filed in on the bottle
• When your sample gets to the lab, they will need to know who the test results are for
2. Empty your bladder (go to the toilet and flush away the urine as normal) and record the time e.g. 8 am.
Imagine your bladder is a bucket, to measure the volume of urine produced over 24 hours you need to start with an empty bucket.
3. The next time you need to urinate, collect the urine in the collection container supplied (or transfer it from your own tub)
• This is the first batch of liquid in your bucket and since you recorded the time you emptied your bladder this is the amount of urine produced over that time period
• If you need a bowel movement, any urine passed with the bowel movement should be collected but try not to include faeces with the urine collection.
• Store the urine in a cool, dark place, such as the refrigerator, if possible
4. Continue to collect your urine for the next 24 hours
• You may want to leave a note (or the container) on top of the toilet, so you don’t miss any collections (i.e. flush your urine away), especially if you get up to urinate at night
5. 24 hours later (e.g. at 8 am if that is when you first emptied your bladder), empty your bladder and collect your urine for a final time. Again, record the time you finished the collection.
• This represents the volume of urine produced over that 24-hour period
• Ensure the lid of the container is on securely
6. Take your sample to your GP or lab (depending on where you have been asked to take it) as soon as possible
What happens to the sample when it gets to the laboratory?
1. The urine volume is measured
• Usually the laboratory will weigh your collection container with your 24-hour urine collection in it.
• They will then take a small (e.g. 20 ml) sample for later testing and discard the rest
• They will then measure the empty container and calculate the difference in weight
• 1 ml of water weighs 1 gram so the volume can be easily calculated
2. It depends what the test is for:
• They may measure the pH of the urine
• They may measure the creatinine concentration to see how concentrated/dilute the urine sample is (depends on how much you drank over the collection period)
• They may be able to measure the requested test in the urine quickly (e.g. urine protein)
• They may have to freeze your sample and measure it at a later date if it is a complex test that needs to be performed in a batch
• They may need to freeze your sample and transport it to a specialist laboratory for analysis.
3. Your results will normally be electronically sent to your GP or the doctor who requested the test for you. You can then contact the doctor’s receptionist to request the results or ask to speak to your doctor about the results. Or the doctor may contact you to ask you to make an appointment to discuss the results.