There are hundreds (if not thousands!) of reasons why your healthcare provider might order blood tests for you. Abnormal hormone levels, vitamin deficiencies, diseases, and more can be diagnosed by examining different chemicals and molecules within the blood. Let’s take a look at some of the more commonly ordered blood tests. Complete Blood Count (CBC) This is the go-to test to analyze the three main types of cells within the blood: red blood cells, white blood cells, and platelets. Red blood cells contain a molecule called hemoglobin that carries oxygen from the lungs to the body’s tissues. A CBC shows the number of red blood cells, their size and shape, and the concentration of hemoglobin within each cell. Red blood cells can be low if a person has been losing blood or if they have anemia (low hemoglobin levels). If you are diagnosed with anemia, your doctor will then order more specific tests to determine if your anemia is the result of recent blood loss, low iron levels, or a vitamin B12 or folic acid deficiency. The white blood cells are a key player in the body’s immune system, defending you against potentially harmful organisms. A CBC gives a total white cell count and the percentages of the different types of white cells, which can help your doctor determine what sort of infection your body is fighting (bacterial, parasitic, etc.). Additionally, leukemia, which is a cancer of bone marrow, can be diagnosed if abnormal white cells are present in the blood. A blood platelet count in the normal range is necessary to ensure the blood clots as it should, preventing excessive blood loss from injuries or surgery. Learn more about the blood factors that help the blood clot properly. >> Kidney Function Tests The urea test (or blood urea nitrogen [BUN] test as it is sometimes known) and the creatinine test are the two most commonly order kidney function tests. These two substances are produced during the metabolic process in the body, and it is the kidneys’ job to filter them out of the blood and put them into urine to be excreted out of the body. Elevated levels of urea or creatinine in the blood suggest that the kidneys may not be working properly. Other common kidney function tests include uric acid levels (raised levels can cause gout), electrolytes (the blood’s levels of potassium and sodium), and calcium and phosphate levels. Liver Function Panel The liver converts nutrients into energy for the body and breaks down dangerous toxins. A liver (hepatic) function panel is a blood test to check how well the liver is doing these vital jobs. Your doctor may order a liver function panel if you have symptoms of liver disease like abdominal pain, jaundice, dark urine, and fatigue. This test would also likely be ordered if you have recently been exposed to the hepatitis virus or if you are taking a medicine that could potentially cause liver damage. The test measures the blood’s level of total protein, albumin, bilirubin, and liver enzymes. High or low levels could be indicative of liver damage or disease. Sexually Transmitted Disease (STD) Blood Tests A number of STDs (or STIs [sexually transmitted infections], as they are sometimes called) can be diagnosed by using blood tests.
- Hepatitis: Hepatitis is not always transmitted sexually, so the antibody and antigen testing can be included in the STD tests as well as with Liver Function Tests.
- Herpes: Antibodies for this virus can be measured to assess a past or present herpes simplex infection.
- Human Immunodeficiency Virus (HIV): The screening test looks for the presence of the Human Immunodeficiency Virus antibody. It can take time for the body to produce HIV antibodies (up to 6 months after infection), so they may not be detectable early on in an infection. This is why a repeat test may be needed some time after potential exposure.
- Syphilis: Syphilis has an incubation period of between 9 days and 3 months (the average is 21 days). This test looks for antibodies, which are usually at detectable levels by 6 weeks post-infection. If positive, your doctor will likely recommend a repeat or different test for confirmation.