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 back of the hand, where the veins are relatively close to the surface. Blood samples from children may require a longer appointment and this should be discussed with the receptionist when booking the appointment. They are most commonly taken from the arm. The child's arm will be anaesthetised (numbed) with a special cream before the sample is taken.
There any many different blood tests that can be requested and you can find out more information about these on the NHS Choices website. Below is some information that you may find useful about some of the more frequently requested tests.
Some blood tests require the patient to fast overnight before bloods are taken in the morning. This means that the patient should not eat anything after midnight the night before and SHOULD ONLY DRINK WATER.
Some drinks like tea and coffee with/without milk contain substances which will affect the blood test results and this would mean another blood test.
- Fasting Glucose Samples - Minimum fast 8 hours
- Triglycerides - 10-12 hours fasting sample required
- Oral Glucose Tolerance - Minimum fast 8 hours
(Please note: Glucose tolerance testing will be for a minimum of 2 hours where you will be asked to sit quietly in the surgery and not eat, smoke or use chewing gum.)
- Cholesterol and HDL Cholesterol – Fasting not needed unless specified by GP
It is sometimes necessary to obtain fasting lipid results in diabetic patients. Diabetic patients should not fast on the morning of the test or stop taking their medication or change their existing medication.