Blood tests are a standard part of routine and preventive healthcare. A doctor will often order a blood test before or following a physical examination. A doctor may also order blood tests to evaluate specific conditions.
This article looks at some of the most common types of blood tests and what each test checks for.
During a routine physical, a doctor may order one of the following tests:
Complete blood count
A complete blood count (CBC) measures a variety of the blood’s components, such as:
- red blood cells
- white blood cells
- mean corpuscular volume (MCV) — the average size of a person’s red blood cells
- hematocrit — how much space red blood cells take up in the blood
A CBC test helps a doctor identify blood disorders or diseases, such as anemia, issues with clotting, inflammation, infection, or immune system disorders. A person will need to fast before a CBC test only if their doctor asks them to.
Blood enzyme tests
Blood enzyme tests measure the levels of specific enzymes in the body. The body produces enzymes to help control chemical reactions within the body.
Enzyme blood tests can help a doctor identify specific health problems, including a heart attack. If a doctor suspects a heart attack, they will check the levels of the cardiac troponin enzyme, which the heart releases when it is injured.
Blood clotting tests
A blood clotting test, also known as a coagulation panel, looks for a protein that helps the blood to clot. A doctor may order this test if they suspect the person may have a blood clotting disorder.
If a person is taking warfarin or other blood thinning medications, a doctor will likely use a specific blood clotting test as part of routine monitoring.
If a doctor wants to assess a person’s risk for developing coronary heart disease or other atherosclerotic problems, they will likely order a lipoprotein, or lipid, panel. A lipoprotein panel will provide information about a person’s:
- low-density lipoprotein (LDL) cholesterol level
- high-density lipoprotein (HDL) cholesterol level
- total cholesterol level
- triglycerides level in the blood
According to the Department of Health and Human Services, a person will need to fast for 8 to 12 hours before a lipoprotein panel.
If the results indicate abnormal levels of any cholesterol or triglycerides, it could indicate that the person is at higher risk of developing cardiovascular disease.
Basic metabolic panel
The basic metabolic panel (BMP) measures the levels of different chemicals found in the plasma portion of the blood.
The BMP, also known as a blood chemistry 8 test, provides information about the bones, muscles, and organs.
A doctor will tell an individual whether they need to fast before a BMP test, and for how long.
BMP tests look at the following:
- Uncorrected calcium levels: Abnormal calcium levels could indicate a person has an underlying condition related to their kidneys or bones, cancer, malnutrition, or other diseases.
- Glucose level: Higher than normal blood glucose levels could indicate a person has diabetes or is at risk of developing diabetes. Some people may need to fast before a blood glucose test.
- Kidneys: The presence of excess waste products in the blood, such as blood urea nitrogen (BUN) and creatinine, can indicate a problem with the kidneys.
- Electrolytes: The presence of abnormal electrolyte levels could indicate an issue with dehydration, kidneys, or other underlying conditions.
What a person eats affects the level of specific components in their blood. For example, a person’s blood sugar level, specifically the glucose level, will rise temporarily after eating.
Typically, a person must not eat for several hours before a blood sugar test.
Other tests also require fasting, such as a fasting lipid panel. A person should check with their doctor whether they need to fast before a test.
A person should talk to their doctor about what routine tests they need. A doctor may only order a blood test if they have concerns about other conditions, or they may request a yearly test as part of their preventive health plan.
People taking certain blood thinning medications may need regular blood tests. A doctor can advise them about the frequency of testing based on their risk factors and individual needs.
People may be able to get a blood test at their doctor’s office. However, some tests may require the person to go to a specialized center or the hospital.
Result times can vary based on the type of test that the person has had. For some tests, the wait time is a few minutes. For other tests, the wait time is a few days or more.
A person should ask their doctor how long the results might take to come back. They should also confirm whether the doctor will get the results or whether the lab will send them directly to the individual.
Typically, a blood test involves a healthcare provider inserting a needle into the person’s vein, usually an arm, to draw blood.
Often, a healthcare provider will secure a rubber band around the arm to see the veins in the arm more clearly and clean the area with an alcohol swab before inserting the needle.
The person might feel a pinch that lasts for just a second or two as the needle enters the vein.
Obtaining the sample for a blood test will usually last no longer than 3 minutes.
A person may feel faint following a blood draw. Anyone who feels lightheaded should remain seated until the feeling passes.
Doctors and healthcare providers typically view blood tests as safe with minimal risk of infection at the site of the blood test.
Anyone who experiences signs of infection at the injection site, such as inflammation, swelling, redness, and fever, should contact their doctor.
Rarely, excessive bleeding may occur. People who are taking blood thinners, or who have other underlying conditions that cause excessive bleeding are more likely to experience this
People can discuss any potential concerns about side effects with their doctor before having a blood test.
Blood tests are typically part of routine preventive care. A doctor will often recommend blood tests as part of a physical or if they suspect a person may have an underlying condition.
Blood tests are in and out procedures with minimal to no risk. A person should talk with their doctor about whether they should fast before their test and when they can expect to receive the results.