How to complete the collection correctly — including which void to flush and which to keep.
Collecting urine over a full 24 hours gives a more accurate measurement than a single spot sample. Common reasons your GP might order it:
The container is large (usually 2–3 litres) and provided free by the lab. It may contain a preservative. Ask when you pick it up whether you need to keep it refrigerated — most labs say yes.
Starting at 7 am means you finish at 7 am the next day — early enough to return the sample to the lab before it closes. Write down your start time and keep it handy.
Most 24-hour collections have no dietary restrictions. Exception: if testing for catecholamines (adrenaline/noradrenaline — often for suspected phaeochromocytoma), avoid coffee, tea, bananas, citrus fruit, chocolate, cocoa, vanilla, and alcohol for 24 hours before and during the collection (some labs ask for 48 hours). Avoid strenuous exercise too. Your referral or the lab will confirm the exact list and timing.
When you wake up (or at your chosen start time), go to the toilet as normal. This first void goes down the toilet — do not collect it. Note the exact time. This is when your 24 hours begins.
From this moment, every time you urinate, add it to the collection container. If your container has a preservative in it, don't urinate straight into it — pass urine into a separate clean container first, then carefully pour it in, to avoid splashing the preservative on your skin. This includes trips to the toilet during the day, in the evening, and through the night. Do not miss any — even one missed void can affect the accuracy of the test.
Store the container in the fridge between collections. A dedicated shelf away from food is ideal. In cool weather, a shaded spot in the garage is usually fine — ask the lab if you are unsure. Do not leave it at room temperature.
At the same time you started (e.g. 7 am), empty your bladder one final time and add it to the container. This last void is collected — it completes the 24-hour window. Your collection is now finished.
Seal the container and take it to the pathology lab as soon as possible. Keep it cool during transport — carry it in a bag with an ice pack if it is a warm day. Do not leave it in a hot car. Return it the same morning if possible.
If you miss even one void, the collection is incomplete and the results may be inaccurate. Contact the lab to ask — depending on what is being tested and when the void was missed, they may still be able to use the sample. In most cases you will need to repeat the collection from the beginning the following day.
Plan the collection for a day when you will be mostly at home. If you do need to go out, some people use a small portable container (ask the lab for an extra one) to collect away from home and transfer it to the main container when they return. Keep both containers cool during transport.
Drink your normal amount. Drinking much more than usual dilutes the sample and can lower the concentration of what is being measured. Drinking much less concentrates the sample artificially. Just drink as you normally would during an ordinary day.
Yes — the start time can be any consistent time, not just 7 am. The key is that you start and end at exactly the same time of day, 24 hours apart. Starting in the morning on a weekday is the most practical choice so you can return the sample to the lab the next morning before it closes.
The exact list and timing vary a little by lab, so always check your referral or ask the collection centre. Common instructions are to avoid, for 24–48 hours before and during the collection: coffee, tea, bananas, citrus fruit, chocolate, cocoa, vanilla, and alcohol — these contain compounds that can falsely raise catecholamine results. Avoid strenuous exercise during the collection too.