How Iron Deficiency Anemia Is Diagnosed

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Iron deficiency anemia (IDA) is the most common type of anemia. Anemia results when red blood cells (RBCs) are low in numbers or low in hemoglobin—a protein in the RBCs that helps to carry oxygen to your tissues.

IDA occurs when the body doesn’t have enough of the mineral iron. The body needs iron to make hemoglobin. When there isn’t enough iron in the bloodstream, the rest of the body cannot get the oxygen it needs.

Many different things can cause anemia. Often, an underlying condition is a cause, which makes it vital to get a prompt diagnosis and treatment. Your doctor will use a variety of tools to diagnose IDA and its underlying cause.

Keep reading to learn about how IDA is diagnosed, including through self-checks, physical exams, lab work, and other tests.

Bloodwork

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Self-Checks/At-Home Testing

Your doctor will decide what types of testing are needed based on what you tell them. Mild to moderate IDA may not have symptoms. In this instance, your doctor will determine whether you have IDA through blood work or by checking for other problems.

If you develop severe anemia, you are more likely to experience symptoms, and these will range from mild to moderate. Symptoms of IDA are similar to those of other types of anemia. 

The most common symptom of IDA is chronic fatigue, which occurs because the body doesn’t have enough healthy red blood cells to carry oxygen to all of its organs and tissues.

Additional symptoms include shortness of breath, dizziness, headache, cold hands and feet, and weakness. Infants and young children with IDA might experience poor appetite, slowed growth and development, and behavioral problems.

Additional signs and symptoms IDA might include:

  • Brittle nails
  • Swelling and soreness of the tongue
  • Cracks on the sides of the mouth or mouth ulcers
  • An enlarged spleen
  • Frequent infections

Some people with IDA may experience a symptom called pica. This means they have unusual cravings for nonfood items, such as ice, dirt, or paper.

Others may end up developing restless legs syndrome (RLS). RLS is a disorder that causes the urge to move the legs. It also causes unusual or unpleasant sensations in the legs. These symptoms are common at night and may affect the ability to get a good night’s sleep.

In making a diagnosis, your doctor will ask about signs and symptoms you are experiencing and past problems with low iron or anemia.

In anticipation of your appointment with your doctor, jot down what symptoms you have been experiencing, what medications you take, and what type of diet you follow. Your doctor will also want to know if you are pregnant.

Physical Examination

Your doctor will do a physical exam to look for signs that you might have IDA. They may look at your skin, gums, and nailbeds to see if they are pale. They may also listen to your heart for rapid and irregular heartbeats and your lungs for rapid or uneven breaths.

Your doctor might also examine your abdomen and check if your liver or spleen might be enlarged.

Labs and Tests

Iron deficiency anemia is diagnosed using lab work. Your doctor will request a complete blood count (CBC) to see if your red blood cell counts, hemoglobin, hematocrit, or mean corpuscular volume (MCV) could suggest anemia.

Hematocrit is the percentage, measured in volume, of how much blood contains red blood cells. Measuring the percentage can reveal whether there are too many or too few RBCs.

The MCV is the value of the average size of RBCs in a blood sample. The MCV offers some helpful information, but it is generally not used alone. It is used with other lab work to narrow down a diagnosis.

Your doctor may also request additional lab tests, including a ferritin measure test, reticulocyte count, transferrin level, and peripheral smear:

  • A ferritin test helps your doctor find out how much iron your body has used. Ferritin is a protein that assists iron storage. It is not unusual for your blood iron to be normal even when total iron is low. Your doctor usually does this test along with other tests.
  • A transferrin level and/or total iron-binding capacity test will measure how much transferrin isn’t carrying iron in the blood. Transferrin is a protein that carries iron into the blood. People with IDA have high levels of transferrin that have no iron.
  • A reticulocyte count test looks to see if you have lower than normal new red blood cells.
  • A peripheral smear may show smaller, oval-shaped cells that have pale centers. With severe IDA, white blood counts (WBCs) will be low, and platelet counts are either high or low.

Your doctor may request additional testing, including hormone level testing and an erythrocyte protoporphyrin test. Erythrocyte protoporphyrin is a building block for hemoglobin.

Children may need to have their lead levels checked. Lead makes it harder for the body to produce hemoglobin.

Testing for Underlying Conditions

If your doctor thinks your IDA is caused by another condition, they may do additional testing.

Inflammation caused by a variety of inflammatory conditions can lead to IDA. This is because inflammation promotes a hormone called hepcidin, which can stop iron regulation in the body.

Inflammation can also affect the way the body absorbs and uses iron. You should let your doctor know if you live with an inflammatory condition like inflammatory arthritis or inflammatory bowel disease.

If your doctor thinks internal bleeding might be causing your IDA, they may order testing to determine the source. They may order a fecal occult blood test to look for blood in the feces, which might occur with intestinal bleeding.

Additional testing might include endoscopy to look at the gastrointestinal (GI) tract or an esophagogastroduodenoscopy (EGD) that examines the stomach lining, esophagus, and the upper part of the small intestine. They may also request a colonoscopy to examine the lower part of the large intestine and lining of the colon. All these tests look for sources of GI bleeding.

An ultrasound might be done for people with excessive menstrual bleeding to determine what might be causing the bleeding. Heavy menstrual bleeding has many causes, including uterine fibroids, hormone imbalances, or a nonhormonal intrauterine device for birth control.

Differential Diagnoses

There are many different forms of anemia, often identified by their causes. The signs and symptoms of anemia might be similar, although different underlying causes might cause different symptoms.

If the anemia is caused by a chronic disease, that disease can mask anemia symptoms. Anemia might be detected by tests for another condition.

Other common types of anemia are pernicious anemia, aplastic anemia, and hemolytic anemia.

Pernicious anemia: This type of anemia occurs when the body doesn’t make enough healthy red blood cells because it cannot absorb enough vitamin B12 from food. It affects people who have conditions that prevent them from absorbing B12 and people who do not get enough B12 from their diets.

Aplastic anemia: People with this type of anemia have lower numbers of red blood cells, in addition to low numbers of other blood cells. It appears because the bone marrow is damaged and cannot make enough red blood cells, white blood cells, and platelets.

Causes of this type of anemia are either inherited (a genetic condition that damages bone marrow) or acquired (e.g., from cancer treatments or exposure to certain toxins).

Hemolytic anemia: This type of anemia occurs because the body does not make enough red blood cells to replace destroyed ones. Sometimes this is related to an acquired condition where the body gets a signal to destroy red blood cells that are young, healthy, and normal.

Other times it is an inherited condition, with problems related to the genes responsible for red blood cells.

All anemias are diagnosed in the same way, but testing, especially blood work, will help to determine the type and/or source. Fortunately, most anemias are treatable once you have an accurate diagnosis.

Summary

Iron deficiency anemia is diagnosed by reported symptoms, physical examination, and laboratory testing. It must be distinguished from other forms of anemia. Your healthcare professional will also look for underlying conditions that could lead to iron deficiency anemia.

A Word From Verywell

You should make an appointment to see your doctor if you are experiencing high levels of fatigue and don’t know why. Fatigue has many causes, and iron deficiency anemia is only one.

Your doctor can administer testing and determine the source of your fatigue and other symptoms. In cases where an underlying condition is causing symptoms, your doctor will work to get a proper diagnosis and start treatment before things get progressively worse.

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7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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