Widely used blood tests

Blood tests can be used in a number of ways, such as helping to diagnose a condition, assessing the health of certain organs or screening for some genetic conditions.

This page describes the following commonly used blood tests:

For more information about a wider range of tests, search the blood test A-Z index on Lab Tests Online UK.

Blood cholesterol test

Cholesterol is a fatty substance mostly created by the liver from the fatty foods in your diet and is vital for the normal functioning of the body.

Having a Hyperlipidemia can contribute to an increased risk of serious problems such as heart attacks and strokes .

Blood cholesterol levels can be measured with a simple blood test. You may be asked not to eat for 12 hours before the test (which usually includes when you're asleep) to ensure that all food is completely digested and won't affect the result, although this isn't always necessary.

Find out moreabout diagnosing high cholesterol and read about cholesterol tests on Lab Tests Online UK.

Blood culture

Thisinvolves taking a small sample of blood from a vein in your arm and from one or more other parts of your body.

The samples are combined withnutrients designed to encourage the growth of bacteria. This can help show whether any bacteria are present in your blood.

Two or more samples are usually needed.

It's likely to be painful and is only carried out in hospital.

A blood gas test is used to check the balance of oxygen and carbon dioxide in your blood, and the balance of acid and alkali in your blood (the pH balance).

A pH imbalance can be caused by:

  • problems with your respiratory system, such as pneumonia or chronic obstructive pulmonary disease (COPD)
  • problems affecting your metabolism (the chemical reactions used by the body to break down food into energy), such as diabetes, kidney failure orpersistent vomiting

These only require a small "pin prick" of blood for testing.

This isknown as rhesus disease .

If you dont already know your blood type, your blood will be tested at least once during your pregnancy to determine if theres a risk of rhesus disease.

If it takes a long time for your blood to clot, it may be a sign of a bleeding disorder such as haemophilia or von Willebrand disease .

A type of coagulation test called the international normalised ratio (INR) is used to monitorthe dose of anticoagulants , such as warfarin , and check that your dose is correct. The quicker they fall, the more likely it is there are high levels of inflammation.

An ESR is often used to help diagnose conditions associated with inflammation, such as:

  • arthritis
  • endocarditis
  • Crohn's disease
  • giant cell arteritis
  • polymyalgia rheumatica

Along with other tests, an ESR can also be useful in confirming whether you have an infection.


By measuring the levels of these enzymes and proteins, it's possible to build up a picture of how well the liver is functioning.

This can help to diagnose certain liver conditions, including hepatitis , cirrhosis (liver scarring), and alcohol-related liver disease .

on Lab Tests Online UK.

Thyroid function test

This test is used to test your blood for levels of thyroid-stimulating hormone (TSH), and, where needed, thyroxine and triiodothyronine (thyroid hormones).

If you have low or high levels of these hormones, it could mean you have a thyroid condition such as an underactive thyroid or overactive thyroid .

on Lab Tests Online UK.

Content supplied by the NHS Website

Medically Reviewed by a doctor on 30 Nov 2016