It depends on the type of blood test you're having. The healthcare professional arranging your test will tell you if you need to do anything to prepare for it.
You can eat and drink as normal before some blood tests. But if you're having a "fasting blood test", you will be told not to eat or drink anything (other than water) beforehand. You may also be told not to smoke before your test.
Common fasting blood tests
Examples of blood tests that may require you to fast include:
- a fasting blood glucose test (used to test for diabetes) – you may be asked to fast for 8 to 10 hours before the test
- an iron blood test (used to diagnose conditions such as iron deficiency anaemia) – you may be asked to fast for 12 hours before the test