Blood tests are useful tools for uncovering many diseases and disorders. They detect abnormally high or low levels of substances that may indicate a variety of conditions, including sources of pain ranging from Lyme disease to sickle cell anemia to types of arthritis.

Blood tests may be ordered for a number of reasons, including:

• Screening for a disease before symptoms appear
• Helping determine a diagnosis
• Monitoring the progression of a disease
• Monitoring the effectiveness of a patient’s treatment

Common blood tests include:

• Complete blood count (CBC). Measures the number of red blood cells, white blood cells and platelets.
  
  
• C-reactive protein test and sedimentation rate. Indicate inflammation.
  
  
• Enzyme test. Detects damage to tissues and assesses functioning of the body’s systems.
  
  
• Rheumatoid factor test. Measures an antibody that may indicate diseases such as rheumatoid arthritis.
  
  
• Waste product test. Helps detect gout and kidney damage due to conditions such as lupus.

Depending on the amount of blood required for the test, blood can be drawn from a vein puncture (venipuncture), artery puncture (arterial puncture) or skin puncture. Obtaining a blood sample takes only a few minutes, and most patients find blood tests to be virtually painless.

Some blood tests require fasting, but most involve little or no preparation, and patients can generally return to their usual daily activities afterward. Additional diagnostic tests such as urinalysis, imaging tests or biopsy may be necessary to confirm a diagnosis.