As the body’s main carrier of nutrients, waste products and oxygen, the blood offers physicians a very important tool for diagnosing and monitoring health. Many forms of heart disease can be detected by various types of blood tests.

During a blood test, a medical professional will take some blood, either by using a finger prick (or heel in the case of a baby) to obtain just a few drops or by using a needle to obtain a larger quantity. In adults, blood may be taken from a vein (venipuncture) or artery (arterial puncture).

The blood may then be tested for many different factors. For example, the physician may need to know the number of red or white blood cells present, the levels of various blood fats,or the amount of oxygen or carbon dioxide circulating in the blood.

Obtaining a blood sample takes only about five minutes, and most patients find the procedure to be virtually painless. For most blood tests, there is very little preparation, and people can generally return to their usual daily activities after testing.