Why can a blood sample fail?

Sometimes the lab may not be able to perform any or all of the tests on your blood sample. This is more common with finger-prick tests where you might have found it difficult to collect your sample, especially if this was your first attempt. This doesn't necessarily arise because you did anything wrong and most people find that they can collect a successful sample on their second attempt. 

The good news is that we will help you to collect a new sample, and let you know what you can do to make sure everything goes to plan the next time.

There are 5 main problems that can make it difficult for a laboratory to run a blood test:

Clotted Sample

Clotting can occur if your blood is not mixed thoroughly after collection (the tube needs to be inverted 5 - 10 times) or if you have taken a long time to collect your sample and the blood has clotted before mixing takes place. If you are taking a finger-prick sample then we recommend giving the container a gentle swirl after each drop of blood has been collected, to ensure that it mixes with the sample contents.

Haemolysed Sample

A haemolysed sample occurs when some red blood cells burst and the haemoglobin within these escapes and spoils the surrounding sample. With finger-prick samples this can happen if your finger has been squeezed too hard or if you scraped your finger on the side of the tube rather than letting the droplets drop down the tube gently. Venous blood tests can also be affected by haemolysis when there are difficulties in taking the sample.

Insufficient Sample

When your sample is received at the laboratory it is spun and separated into the blood cells and the liquid (plasma) that surrounds the cells. If the amount of blood taken is insufficient, the lab will struggle to produce enough plasma. The usual cause for this is if the blood vial (container) is underfilled.

Please note that in some cases the lab is still able to do a partial analysis of the sample. If this is the case you will receive these results. In other cases, however, they are not able to analyse the sample at all.

The Sample is too old

If a sample is delayed in the post, it may be too old to be used for testing when it arrives.  Some tests are more sensitive than others.  We try to limit the time your sample spends in the post:  We ask that you only send samples on weekdays, avoiding weekends and public holidays.  We provide a tracked postage returns envelope in each test kit. Please make a note of your unique tracked postage number so that you can track your sample. You can find this number under the barcode on the postage sticker inside your kit.  

If your sample is not labelled correctly

If your sample is not labelled or there is information missing the lab may not be able to use this.  Working to strict UKAS guidelines the labs must produce accurate medical records, and a sample without a completed label is not permissible.