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What is this test for?
This test is to see if your body is still making any of your own insulin.
When should I do the test?
Please collect a urine (wee) sample on a Sunday, Monday, or Tuesday to allow time for it to be sent down to the laboratory and processed. This usually takes three days.
This urine sample should be collected after your largest meal that contains carbohydrates (for example, bread, rice, pasta, potatoes, cereals).
Please do not collect this sample when you are on your menstrual period.
How should I collect the sample?
You will be given a tube with a red lid to collect your sample in. The tube contains powder which acts as a preservative. Do not throw the powder away.
Please follow the instructions below:
- Please pass urine (have a wee) before your largest meal of the day. Flush this away as normal. Do not collect this.
- If you have insulin for this meal, take your usual dose. Make sure you have plenty to drink during the meal.
- About two hours after your meal, collect the urine sample into the tube. When collected, tighten the lid, and turn the tube upside-down and back ten times.
- Write the date and time on this tube. Please make sure the sticker on the container is not wet as otherwise it can get removed on transit to the laboratory.
- Place the red-lid tube in the blood sciences bag and drop off either at your GP surgery or the hospital as soon as you can, either the same day or the next day.
When will I get a result?
The result takes about two weeks to return.
More information about a c-peptide result can be found here: C-Peptide Test: MedlinePlus Medical Test.
Who can I contact for further information and advice?
Royal Sussex County Hospital
Princess Royal Hospital
The information in this leaflet is for guidance purposes only and is in no way intended to replace professional clinical advice by a qualified practitioner.