Quick answer
What are blood tests?
A blood test is a sample of blood taken from a vein and checked in a laboratory to assess your health, diagnose conditions or monitor medicines. Most blood tests need no special preparation, although some require fasting. A phlebotomist usually takes the sample, and the results are sent to your GP.
What are blood tests for?
Blood tests are used to screen for, diagnose and monitor a wide range of conditions. They are among the most common investigations carried out on the NHS.
What happens when you have blood taken
A tourniquet is placed around your arm, the skin is cleaned, and a needle is inserted into a vein to draw the sample. Several tubes may be filled if a number of different tests are needed.
How to prepare for a blood test
Follow the instructions from your GP or hospital about fasting and the timing of your test, as some tests only give accurate results under certain conditions. Let the staff know if you take blood-thinning medicines or have a history of fainting during blood tests.
Understanding your blood test results
Reference ranges vary between laboratories and with your age, so results are always read in context. Mild abnormalities often need a repeat test before any action is taken, and your GP will explain what your results mean.
Common questions about the blood tests
- Do blood tests hurt?
- You usually feel a brief sharp scratch as the needle goes in, and it is over within seconds. Some people get a little bruising afterwards, which soon fades.
- Do I need to fast before a blood test?
- Some tests, such as fasting glucose and lipid profiles, usually need 8 to 12 hours without food beforehand. Water is fine unless you are told otherwise, so follow the instructions you are given.
- How long do blood test results take?
- Many blood test results are available within two to five days. Some specialised tests take longer, and your GP surgery can tell you when to expect yours.
- What happens if my blood test results are abnormal?
- Your GP interprets the results in the context of your health and symptoms. Depending on what they find, they may repeat the test, start treatment, or refer you for further investigation.
- What free NHS health checks and screenings am I entitled to?
- Adults in England aged 40–74 are invited for a free NHS Health Check every five years (blood pressure, cholesterol, diabetes risk). Screening programmes include bowel cancer (home test kit), breast screening (mammogram), cervical screening (smear test), and abdominal aortic aneurysm screening for men at 65. You will normally be invited by letter — check with your GP if you think you have missed one.