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
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.
Fasting Blood Tests
Some blood tests can be taken while you are seeing the GP; where possible we do this to save you time. However, for some tests to be accurate (blood sugar tests, fats in blood) we need you to have fasted before a booked blood test with the practice nurse. This means no food or drinks (including tea, coffee, diet fizzy drinks as these often contain caffeine which can elevate blood sugar) other than water for at least 12 hours prior to your blood test appointment. This will ensure we get an accurate sample for testing.
You can find out more about blood tests, their purpose and the way they are performed on the NHS Choices website.