What happens during a blood test and what could the results show?
Blood tests can be a simple way of getting more information about what’s going on inside your body. But what’s involved? Clinic Lead Carol Nichols explains.
Why have a blood test?
Blood tests are usually done to check how your body copes with illness, injury, inflammation, infection and some types of medication. Blood needs a very precise balance in order for your body to work well. If blood test results are abnormal, it gives the doctors a good indication of how to treat you or prevent problems occurring in the future.
How will my blood be taken?
A rubber strap called a tourniquet is wrapped tightly around your upper arm – this helps to bring the vein that runs inside your elbow to the surface, so that it is easier to find.
The skin around the vein is cleaned with a sterile alcohol wipe. A small needle is inserted into the vein and a small blood bottle is then attached and the sample is taken.
After the needle is removed, gauze is put over the puncture site and you will be asked to hold it for a few minutes. Bleeding from a vein usually stops very quickly, but may take a few minutes if you take blood-thinning medication.
Do I need to to prepare for a blood test? Will I need other tests?
Occasionally you may need to fast (not eat) before your blood test, we will let you know if this is required. Unless you have been told not to, have a drink of water before your test. If you’re dehydrated, it can be more difficult to find your vein.
Sometimes the results of blood tests mean that the doctor may want to do other tests, such as a scan on your heart or kidneys, or an electrocardiogram (ECG).
What happens to my blood after the test?
Each bottle is labelled with your name, date of birth, when the blood was taken, and has a different coloured top according to the type of test. Then they are then sent to the lab for analysis via specialist courier service.
What will my blood be tested for?
Blood can be tested for many different things, including to check cholesterol and blood glucose levels. These tests help monitor your risk of heart and circulatory diseases and diabetes, or how your condition is being managed.
Tests for different chemicals and proteins can indicate how your liver or kidneys are working. A test for troponin can help to diagnose a heart attack, and a test for brain natriuretic peptide (BNP) can help diagnose heart failure.
If you take warfarin, your INR level (a measure of how quickly your blood will clot) will be tested regularly to make sure that you are prescribed the correct dose.
I am nervous about having a blood test.
What can I do?
Many patients feel a little anxious before a blood test.
Our experienced medical team are here to help guide and reassure you. Please tell us if you are nervous, and we will take extra special care of you on the day – that’s what we are here for. You could always ask someone to come with you for additional support too – just let us know.