There are several types of blood tests that can be used to diagnose anemia. A complete blood count (CBC) is most commonly used, but other types of tests can also be useful. Some tests may also help determine what’s causing anemia.
Anemia happens when the level of red blood cells in your body is too low. Red blood cells are needed to carry oxygen to all the cells in your body.
In most cases, anemia can be easily diagnosed with specific blood tests. These tests look at factors such as how many red blood cells you have and the health of your blood cells. This information is then used to confirm a diagnosis of anemia.
This article takes a closer look at the types of tests that can be used to diagnose anemia and what the results mean.
There are a few common blood tests that can be used to diagnose anemia. The exact tests a doctor or healthcare professional may order depend on your symptoms, medical history, and the results of other tests.
Let’s take a closer look at some of the most common blood tests that are used to diagnose anemia.
Complete blood count
A complete blood count (CBC) is usually the first test that’s ordered to diagnose anemia. It’s often used to help diagnose other conditions, too.
A CBC measures the following levels in your blood:
When it’s used for anemia, doctors pay particularly close attention to your red blood cell and hemoglobin levels.
Another value that’s usually shown on a CBC, which may help diagnose anemia, is mean corpuscular volume. If this value is low, it may indicate a microcytic anemia, such as iron deficiency, and if this value is high, it may indicate a macrocytic anemia (B12 deficiency).
Sometimes anemia is caused by an iron deficiency. If a doctor thinks this may be the case, they’ll order a blood test known as an iron panel or serum iron test. This test will measure the level of iron in your blood.
An iron panel typically includes several lab values, including:
These values may help determine whether the cause of anemia is iron deficiency or chronic inflammation.
A reticulocyte count measures the number of immature red blood cells in your blood. It can help a doctor determine whether your bone marrow is producing enough red blood cells. This test is important because it can help pinpoint the cause of anemia.
For instance, if your CBC results show you have a low red blood cell count, but your reticulocyte count shows you have a high immature red blood cell count, it could mean you’re losing blood somehow.
Conversely, if you have low levels of both mature and immature red blood cells, it may mean your body isn’t making enough red blood cells.
A blood smear is another test that can be used to help pinpoint the possible cause of anemia.
A blood smears is done by spreading a drop of blood on a medical slide. A staining liquid is then added to the slide, which can help find any abnormalities in the shape of the blood cells.
This test may be particularly helpful in diagnosing sickle cell anemia, which is characterized by crescent-shaped red blood cells. It may also be helpful for diagnosing some nutritional deficiencies, which can cause very large red blood cells.
- If a type of anemia called hemolytic anemia is suspected (red blood cells are destroyed faster than the bone marrow can make them), the following tests may be done:
- Lactate dehydrogenase (LDH) test: This test measures a type of enzyme known as LDH that’s found in almost all tissues in your body. If your LDH levels are high, it may mean certain tissues in your body have been damaged by disease (such as anemia) or injury.
- Haptoglobin test: A haptoglobin test can help detect what type of anemia you have and possibly also help determine the cause of increased red blood cell destruction.
- Indirect bilirubin: Indirect bilirubin is the difference between your total and direct bilirubin. This level can increase if your body destroys too many red blood cells.
- Vitamin B12 and folate levels: These are commonly checked to rule out vitamin deficiency as a cause.
- A Coombs test: This is often done if an autoimmune disease is suspected as the cause of anemia.
Different factors such as your age, race, and the altitude at which you live can affect what’s considered a healthy range for various anemia blood tests. Talk with a doctor about what’s considered a healthy range for you.
- CBC (red blood cells): Healthy results for a red blood count are
5 to 6 million cells per microliter (cells/mcL)for men and 4 to 5 million cells/mcLfor women. Values below these levels may indicate anemia.
- CBC (hemoglobin): Healthy results are above
14 grams per deciliter (gm/dL) for men and above 12 gm/dL for women.
- Iron: Healthy iron levels in the blood start at
10 micromoles per liter (µmol/L).
- Ferritin: Ferritin is measured in an iron panel. Healthy levels start at
40 micrograms per liter (µg/L) for men and 20 µg/L for women.Levels below 10 µg/L may be a sign of anemia.
- Reticulocyte: Normal results for reticulocytes in adults are between
0.5 and 2.5%.
- Blood smear: A blood smear looks at the shape of your blood cells. Abnormally shaped red blood cells can be a sign of sickle cell anemia.
If your blood test results don’t confirm an anemia diagnosis, a doctor will likely order additional tests to determine what’s causing your symptoms.
We use “women” and “men” in this article to reflect the terms that have been historically used to gender people. But your gender identity may not align with how your body responds to this disease. A doctor can help you better understand how your specific circumstances will translate into diagnosis, symptoms, and treatment.
In some cases, additional tests may be necessary. This typically happens when a doctor knows you have anemia but needs more information to determine what’s causing it. The types of tests that may be ordered include:
- Bone marrow biopsies and aspirations: Bone marrow aspirations and biopsies are done by inserting a long, thin, and hollow needle into a bone to extract bone marrow fluid and tissue. This allows doctors to see if the bone marrow is healthy and able to make enough healthy blood cells.
- Urinalysis: A urinalysis test looks for blood in your urine and checks your kidney function.
- Endoscopy: An endoscopy is done by inserting a thin tube with a tiny camera on the end into your mouth and through the upper digestive tract. This allows doctors to look for bleeding in your esophagus, stomach, and small intestine.
- Colonoscopy: A colonoscopy is done by inserting a thin tube with a small camera into the rectum to look for bleeding in the colon (large intestine).
- Genetic tests: A genetic test can look for changes to the genes that are programmed to make red blood cells.
Anemia symptoms sometimes develop slowly. In other cases, they can come on suddenly. The underlying cause of anemia is a factor in determining how quickly symptoms develop.
No matter how quickly or slowly they develop, when symptoms appear, they typically include:
If you experience any of these symptoms for more than a week, it’s a good idea to make an appointment with a doctor. They can help diagnose the cause of your symptoms and create the right type of treatment plan for you.
If you have symptoms such as ongoing fatigue, weakness, or dizziness, a doctor will likely order one or multiple types of blood tests to determine if you have anemia. A test called a CBC is often the first test that will be done to help diagnose anemia. This test measures the level of red blood cells in your blood and is a reliable indicator of anemia.
Other common blood tests include an iron panel, a reticulocyte test, and a blood smear. These tests can also help doctors determine the underlying cause of anemia and how to best treat this condition.