What Do Common Blood Tests Check For?
Learn what CBC, cholesterol, glucose and other blood tests show
Learn what CBC, cholesterol, glucose and other blood tests show
Key Takeaways
- Common blood tests can reveal important information about your health.
- A CBC can help identify anemia, infection and blood disorders.
- Glucose, A1C and cholesterol tests help assess chronic disease risk.
- Talk with your doctor about what your blood test results mean.
Blood tests are a common way for your doctor to learn more about your health. A small blood sample can help check for conditions, such as anemia, diabetes, high cholesterol and thyroid problems.
“From checking your cholesterol levels and thyroid function to diagnosing infections, diseases and other conditions, blood tests are often the first step in diagnosing dozens of conditions,” says Fatma Deif, MD, an internal medicine physician at Scripps Clinic Rancho San Diego.
Your doctor may order blood tests as part of preventive care or to learn more about certain symptoms or health risks. Blood work also can help track a condition, see if treatment is working or check how medications are affecting you.
Having blood drawn is generally safe and takes only a few minutes. A phlebotomist usually takes a small sample from a vein in your arm. You may feel a brief pinch when the needle goes in.
Most blood tests require little to no preparation. Some may require fasting, so follow your care team's instructions before your test.
What are the most common blood tests?
The blood tests you need depend on your age, health history, symptoms and risk factors. Common tests include a complete blood count, metabolic panel, cholesterol test and blood sugar tests. Your doctor may order other types of blood tests if you have certain symptoms or conditions.
Complete blood count
A complete blood count (CBC) measures several components of your blood and can help identify anemia, infection and signs of certain blood or bone marrow disorders.
A CBC typically includes:
Red blood cell count: Red blood cells carry oxygen from your lungs throughout your body. A low count may occur with anemia, blood loss and other conditions.
White blood cell count: White blood cells are part of your immune system. High or low counts can occur with infections, immune disorders, medications and other conditions.
Platelet count: Platelets help your blood clot. Too few can increase the risk of bleeding; a high platelet count may occur with certain medical conditions and sometimes increase the risk of blood clots.
Hemoglobin: Measures the oxygen-carrying protein in red blood cells. Low hemoglobin is a common sign of anemia.
Hematocrit: Measures the percentage of your blood made up of red blood cells. Low levels may occur with anemia, while dehydration can cause higher levels.
Mean corpuscular volume (MCV): Measures the average size of your red blood cells and can help identify different types of anemia.
A CBC may also include a differential, which measures the different types of white blood cells.
Basic and comprehensive metabolic panels
Metabolic panels measure substances in your blood that provide information about how your body is functioning.
Basic metabolic panel
A basic metabolic panel (BMP) typically measures:
Blood glucose
- Calcium
- Sodium
- Potassium
- Chloride
- Carbon dioxide or bicarbonate
- Blood urea nitrogen (BUN)
- Creatinine
A BMP provides information about kidney function, glucose, electrolytes, calcium, acid-base balance and metabolism.
Comprehensive metabolic panel
A comprehensive metabolic panel (CMP) includes the BMP tests plus measurements of proteins, bilirubin and liver enzymes that can provide additional information about liver function.
Lipid panel
A lipid panel, also called a cholesterol panel, measures fats in your blood and can help assess your risk of heart disease and stroke.
It generally includes:
- Total cholesterol
- LDL (“bad”) cholesterol
- HDL (“good”) cholesterol
- Triglycerides
Some lipid tests can be done without fasting. Your doctor will let you know if you need to fast beforehand.
Blood glucose and A1C tests
Blood glucose tests measure the amount of sugar in your blood and can help screen for, diagnose and monitor prediabetes and diabetes.
A fasting blood glucose test requires you to avoid eating for a certain amount of time before the test. An A1C test measures your average blood sugar level over the past two to three months and usually does not require fasting.
These tests can help identify diabetes and guide treatment. Diabetes can raise your risk of heart disease and other health problems.
Thyroid blood tests
Thyroid blood tests can show whether your thyroid is working as it should. A common test measures thyroid-stimulating hormone (TSH), which helps control how much thyroid hormone your body makes.
Abnormal TSH levels may indicate an underactive or overactive thyroid. Your doctor may order other thyroid tests, such as T4, for more information.
Troponin test
A troponin test helps doctors check for damage to the heart muscle, including damage from a possible heart attack.
Troponin is a protein found in heart muscle cells. When the heart muscle is injured, troponin can enter the bloodstream. Higher-than-normal levels may be a sign of heart muscle damage.
This test is not usually part of routine blood work. It is most often ordered when symptoms or other findings suggest a possible heart problem.
Coagulation tests
Coagulation tests measure how well your blood clots and how long the clotting process takes.
Common tests include prothrombin time (PT) and international normalized ratio (INR), a standardized calculation based on PT. These tests may be used to check unusual bleeding or clotting and to monitor people who take warfarin, also known by the brand name Coumadin.
Another test, activated partial thromboplastin time (aPTT), checks a different part of the blood-clotting process.
Pregnancy blood test
A pregnancy blood test measures human chorionic gonadotropin (hCG), a hormone produced by the developing placenta during pregnancy.
Blood tests can detect small amounts of hCG and may be used to confirm pregnancy very early or measure hCG levels over time.
HCG testing has other medical uses. It can help diagnose or monitor certain tumors and cancers. But it is not a routine cancer screening test.
How should you prepare for a blood test?
Most blood tests require little to no preparation. If you need to fast, your care team will tell you how long to avoid food and whether to keep taking your medications.
Do not stop prescription medications or supplements unless your doctor tells you to do so.
Understand your blood test results
If your doctor orders blood work, ask what the tests are checking for and whether you need to do anything before the test.
Blood test results can provide useful information about your health, but they are only one part of the picture. Talk with your doctor if you have questions about what your results mean.
Scripps patients can view many test results securely in MyScripps and contact their care team with questions.