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Blood Tests

Blood tests help doctors check for certain diseases and conditions. They also help check the function of your organs and show how well treatments are working. NIH - National Heart, Lung, and Blood Institute

Blood Tests

Blood tests help doctors check for certain diseases and conditions. They also help check the function of your organs and show how well treatments are working.

Specifically, blood tests can help doctors:

  • Evaluate how well organs - such as the kidneys, liver, thyroid, and heart - are working
  • Diagnose diseases and conditions such as cancer, HIV/AIDS, diabetes, anemia (uh-NEE-me-eh), and coronary heart disease
  • Find out whether you have risk factors for heart disease
  • Check whether medicines you're taking are working
  • Assess how well your blood is clotting


Blood tests are very common. When you have routine checkups, your doctor may recommend blood tests to see how your body is working.

Many blood tests don't require any special preparations. For some, you may need to fast (not eat any food) for 8 to 12 hours before the test. Your doctor will let you know how to prepare for blood tests.

During a... Read more about Blood Tests

What works? Research summarized

Evidence reviews

Routine blood tests as predictors of mortality in hip fracture patients

Bibliographic details: Laulund AS, Lauritzen JB, Duus BR, Mosfeldt M, Jorgensen HL.  Routine blood tests as predictors of mortality in hip fracture patients. Injury 2012; 43(7): 1014-1020 Available from: http://www.injuryjournal.com/article/S0020-1383(11)00579-1/abstract

Immunochemical versus guaiac fecal occult blood tests

Bibliographic details: Piper M A.  Immunochemical versus guaiac fecal occult blood tests. Chicago, IL, USA: Blue Cross and Blue Shield Association, Technology Evaluation Center. TEC Assessment Program; 19(5). 2004

Blood tests to diagnose fibrosis or cirrhosis in patients with chronic hepatitis C virus infection: a systematic review

This review concluded that many blood tests were moderately useful for identifying clinically significant fibrosis or cirrhosis in hepatitis C virus-infected patients. Despite some limitations of the review and available evidence, the authors' conclusions were suitably cautious, and the limitations of the evidence for some of the tests were acknowledged.

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Summaries for consumers

Fact sheet: Understanding thyroid gland tests

The thyroid gland is a vitally important hormonal gland, which mainly works for body’s metabolism. It is located in the front part of the neck below the voice box and is butterfly-shaped. The functions of the thyroid gland include the production of the thyroid hormones triiodothyronine (T3) and tetraiodothyronine, also called thyroxine (T4).

At a glance: Bowel cancer – screening and prevention

In Germany, you can have bowel cancer screening if you are 50 years of age or older. It is your personal decision whether you take part and which examination you choose. In this text we will give you information about the advantages and disadvantages of the different tests and help you in making a decision.

Fact sheet: Understanding bone examinations

Whether we do exercise, climb stairs or carry water crates – our bones have to prove their stability every day. When we are young, our bodies can handle physical strain more easily than later in life. Nonetheless fractures are not uncommon at a young age, for example in sports accidents. As we grow older, diseases like osteoporosis and signs of wear and tear in the bones become more common. Depending on the problem, different types of bone examinations are considered. We describe the most common ones in this fact sheet.

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Terms to know

A tissue with red blood cells, white blood cells, platelets, and other substances suspended in fluid called plasma. Blood takes oxygen and nutrients to the tissues, and carries away wastes.
Blood Plasma
The clear, yellowish, fluid part of the blood that carries the blood cells. The proteins that form blood clots are in plasma.
Bone Marrow
The soft, sponge-like tissue in the center of most bones. It produces white blood cells, red blood cells, and platelets.
Protein made by the body that brings about a chemical reaction - for example, the enzymes produced by the gut to aid digestion.
Erythrocytes (Red Blood Cells)
A cell that carries oxygen to all parts of the body.
A measure that tells what portion of a blood sample consists of red blood cells. Low hematocrit suggests anemia or massive blood loss.
A protein inside red blood cells that carries oxygen from the lungs to tissues and organs in the body and carries carbon dioxide back to the lungs.
Leukocytes (White Blood Cells)
A type of immune cell. Most white blood cells are made in the bone marrow and are found in the blood and lymph tissue. White blood cells help the body fight infections and other diseases. Granulocytes, monocytes, and lymphocytes are white blood cells.
Platelets (Thrombocytes)
A tiny piece of cell that is made by breaking off of a large cell in the bone marrow. Platelets are found in the blood and spleen. They help form blood clots to slow or stop bleeding, and to help wounds heal. Also called thrombocyte.
One of the major forms of fat that is produced in the liver and found in the blood.

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Other terms to know: See all 10
Blood, Blood Plasma, Bone Marrow

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