All you need to know about blood tests & blood testing

General Health

All your blood testing questions and concerns answered.


Emily Condon
BSc (Hons) Biological Sciences

Share this article

Blood is an invaluable window through which you can look at your inner health - and just a few drops of blood is enough to get a huge amount of information.

What can you find out from a blood test?

Blood tests give a snapshot of your health. You may have a blood test as part of a regular check-up, to help investigate symptoms and diagnose a condition or to keep track of your risk of long-term chronic diseases like heart disease and diabetes. Although blood tests are an invaluable tool to help diagnose a condition or investigate symptoms, you don’t have to be ill to benefit from a blood test. You may have a blood test to check your hormone levels, your vitamin and mineral levels such as vitamin D, B12 and iron, your cholesterol status, organ function or to see how much sugar is in your blood. Whether you are changing your diet, wanting to see how your lifestyle choices are affecting your health, training for a sports event or looking to monitor your hormones there is a blood test for you.

How does a blood test work?

There are 2 main ways to collect a blood sample:

  • A venous blood test involves using a needle to puncture a vein, usually in your arm, and allows a larger volume of blood to be collected.
  • A finger-prick blood test involves using a lancet to prick your finger and allows you to collect a small blood sample. You can do this type of test yourself and it’s less invasive than a venous sample. However, while it can be used to test a wide range of biomarkers it’s not possible to test every biomarker, especially if a larger volume of blood is required.

Where can I get a blood test?

NHS blood tests
Blood testing is one of the many services that the NHS provide and can be done at your GP surgery or your local hospital. Blood testing helps to investigate symptoms further and diagnose a condition. A trained clinician will take your blood, usually from a vein in your arm and the blood will be sent to the lab to be analysed.

Private blood tests
There are a wide range of private blood tests available that can either be completed by a nurse or you can order a blood test online and do it yourself at home. Often with private blood tests, the same accredited laboratories and methods are used to test your sample as the NHS.

Preparing for a blood test

To make your blood draw a smooth process, there are a couple of things you can do beforehand to help increase blood flow:

  • Drink plenty of water — staying hydrated will make it easier to collect your blood sample
  • Stay warm — try having a hot shower before your collect your sample or try jumping on the spot for a minute (this is especially useful for finger-prick blood collection)
  • Certain blood tests may require you to fast which means not eating or drinking anything except water for 8-12 hours before your test.

Does a blood test hurt?

Many people are nervous before they have a blood test and this is completely normal. But the process is quick and straightforward. With a venous blood test, you will feel a little scratch and pinch when the needle goes in but drawing the blood doesn’t hurt at all. It is normal for your arm to bruise afterwards at the site where the needle went in. For a finger prick blood test as the name suggests, you will feel a scratch and pinch on your finger in the area where the lancet went in. This area may be slightly tender for a little while after taking your sample.

Will there be enough blood from a finger prick sample?

There are several private blood tests that require only a small finger prick sample. The option of a finger prick sample will only be available if the laboratory is able to analyse results from only a few drops of blood. For a finger prick test, drinking plenty of water and placing your hands in warm water for a couple of minutes prior to collecting your sample will encourage blood flow to ease the process. A little gentle exercise before taking your sample also helps.

What time should I take my blood test?

Unless stated otherwise, try and take your blood sample in the morning. For hormone tests, this is because hormone levels are at their highest in the morning and this will give the best result. If you need to fast before taking your blood test it is often easiest to do this overnight while you are asleep.

Will a blood sample degrade in the post?

Generally, blood is stable in the post for up to 3 days.

How long does it take to get blood test results?

Blood test results can take anything from one day to a few weeks to come in depending on the test. If you’ve had a blood test through the NHS or a private specialist, your results will be interpreted by them and shared with you. For a private blood test your results will also be interpreted by a doctor and then uploaded online where you can view them.

Do I need a doctor’s referral for a blood test?

Many private blood tests do not require a doctor’s referral. For more specialist tests a doctor’s referral may be required.

This website uses cookies to ensure you get the best experience. Read more