What is a blood test for?
A blood test is when a sample of blood is taken for testing in a laboratory. Blood tests have a wide range of uses and are one of the most common types of medical test. For example, a blood test can be used to:
- assess your general state of health
- confirm the presence of a bacterial or viral infection
- see how well certain organs, such as the liver and kidneys, are functioning
- screen for certain medical conditions
How can I learn more about my blood test?
Your GP will be happy to discuss your blood tests with you and explain what they are for. If you would like to know more, you can visit the NHS Choices website and learn about some of the most widely used blood tests.
Do I need to do anything to prepare for my blood test?
No. The GP or nurse will tell you if there are any special instructions that you need to follow before your test. Occasionally, depending on the type of blood test you may be asked to:
- avoid eating or drinking anything (except water) before midnight prior to the test. This is called a fasting blood test and helps avoid food and drink you have consumed affecting the result.
- stop taking certain medication prior to the test. This would only be done if there is a chance that one of your medication might affect the result of the test.
If you have a phobia of needles or have difficulty giving a blood sample, please let the nurse or GP know. They will be sympathetic and will do their best to support you through the experience.
What happens during a blood test?
A blood test usually involves the phlebotomist taking a blood sample from a blood vessel in your arm. and the usual place for a sample is the inside of the elbow or wrist, where the veins are relatively close to the surface. Blood samples from children are most commonly taken from the back of the hand. The child's hand will be anaesthetised (numbed) with a special cream before the sample is taken. More information about the process of having a blood test is available on the NHS Choices website.
How will I feel after my blood test?
Only a small amount of blood is taken during the test so you shouldn't feel any significant side effects. However some people feel dizzy or faint and if this happens you should tell the nurse or GP carrying out the test so that they can make you feel comfortable. You may also have a small bruised area on your skin where the needle went in but this will soon go.