What Is Iron-Deficiency Anemia (IDA)? Signs, Testing, and Treatment

Iron is an essential building block of red blood cells. These are the cells that carry oxygen to all your muscles and organs. But if you have low stores of iron, it can start to affect your ability to make red blood cells. This is called iron-deficiency anemia (IDA).

Iron deficiency is a common nutritional deficiency in the U.S. It can make people feel tired, have trouble thinking, and affect their mood. And if not treated, it can lead to anemia and serious health issues. So it's important to know the signs and how it's diagnosed. This way, you can get the treatment you need to feel better.

What is iron-deficiency anemia?

Anemia is a general term that means there are not enough red blood cells in the body. Iron-deficiency anemia means these low blood counts are caused by low levels of iron. Many different things can cause anemia, but iron deficiency is the most common cause.

There are a few different ways you can measure the amount of iron and red blood cells in the body. (We explain this in more detail in the testing section.) But it's helpful to know that when someone develops iron deficiency, their blood counts are not affected right away. It takes time for the general progression of iron deficiency to affect blood counts:

• When iron deficiency is mild, the first thing to decrease is ferritin. Ferritin is a protein in the body that stores iron.

• As iron stores get more depleted, less iron binds to transferrin. Transferrin is the protein that transports iron through the blood.

• When iron deficiency becomes more severe, the number of red blood cells eventually starts to decrease.

So in many ways, anemia is a sign of more advanced iron deficiency.

What are the signs and symptoms of iron-deficiency anemia?

The symptoms of iron-deficiency anemia can vary a lot from person to person. Someone with IDA may have few or even no symptoms. And other people with low ferritin - even before iron deficiency progresses to true anemia - may notice pretty significant changes in how they feel.

Symptoms of low iron (or low ferritin) include:

• Fatigue and low energy

• Dizziness

• Headaches

• Trouble concentrating

• Changes in mood

As iron-deficiency anemia develops, additional signs and symptoms include:

• Shortness of breath

• Heart palpitations or a fast heartbeat

• Cravings for ice

• Feeling more cold than normal

• Paleness or increased bruising

• Loss of appetite or nausea

• Brittle nails or hair loss

What causes iron-deficiency anemia?

The most common causes of low iron levels are:

• Decreased iron consumption in the diet

• Decreased iron absorption through the gut

• Increased need for iron, such as during pregnancy

• Blood loss

Blood loss can happen for many different reasons. But some of the more common reasons are:

• Heavy menstruation

• Bleeding from the stomach or intestine, like from a stomach ulcer

• Recent surgery

• Frequent blood donation

Risk factors for iron-deficiency anemia

In general, iron deficiency in the U.S. is more common in young children and women of reproductive age.

More specifically, the risk factors for iron-deficiency anemia include:

• Heavy menstrual bleeding

• Pregnancy or lactation

• Strict vegetarian or vegan diet, or diets low in iron-rich foods

• Cancer in the esophagus, stomach, small bowel, or colon

• Peptic ulcer disease

• Celiac disease

• Crohn's disease

• A history of gastric bypass surgery or intestinal surgery

• Medications, like tetracycline, antacids, or nonsteroidal anti-inflammatory drugs (NSAIDs)

Iron-deficiency anemia can also happen in infants and children. Infants who are born prematurely are at risk for IDA. And children who drink more than 16 oz to 24 oz a day of cow's milk are also at higher risk of developing IDA. This happens because cow's milk interferes with iron absorption from other foods. It can also irritate the gastrointestinal (GI) tract, which causes bleeding.

How do healthcare professionals diagnose iron-deficiency anemia?

To have a diagnosis of iron-deficiency anemia, you need to have lab tests that show both:

• Low red blood cell counts (anemia)

• Low iron stores (iron deficiency)

Diagnosing anemia

There are a few different tests that are all related to red blood cells. And they all can help diagnose anemia. These tests are a standard part of any complete blood count test (CBC):

• Red blood cell count (RBCs): the actual number of red cells in your blood

• Hematocrit (Hct): the concentration of red cells in your blood

• Hemoglobin (Hgb): this measures the amount of hemoglobin, the protein in a red blood cell that holds onto oxygen

• Mean corpuscular volume(MCV): the average size of your red blood cells

The normal ranges for these tests are listed below. So any levels below these are suggestive of anemia. When it comes to iron-deficiency anemia, healthcare professionals pay close attention to the hemoglobin (Hgb) test and the mean corpuscular volume (MCV) specifically.

Newborns and children, depending on their age, have different normal ranges from adults.

Diagnosing iron-deficiency

A low Hgb and low MCV suggest iron-deficiency anemia. But in order to test if iron deficiency is causing your anemia, a healthcare professional will also check your iron levels. Like blood counts, there are a few different tests that can measure iron in your body:

• Ferritin: the amount of ferritin in your blood, the protein that stores iron. This is often the first test a healthcare professional looks at when diagnosing iron deficiency. It will be low.

• Transferrin saturation: the percentage of iron in your blood that's bound to transferrin, the protein that transports iron. This is below normal in IDA.

• Total iron-binding capacity(TIBC): the amount of iron that your blood can potentially carry. Most of the time, a transferrin saturation can replace this test.

• Iron: the amount of iron in your blood. Surprisingly, this test result is not used to make the diagnosis of IDA. The above tests are more helpful.

Every lab uses a different cutoff for normal values. But if you're looking at your results, the report should indicate if your level is normal, high, or low. When it comes to iron-deficiency anemia, healthcare professionals pay close attention to the ferritin and transferrin saturation. The table below summarizes the typical results for someone with IDA.

How is iron-deficiency anemia treated?

To treat iron-deficiency anemia, most healthcare professionals prescribe oral iron supplements. There are many types of iron supplements, but the most commonly prescribed supplements are:

• Ferrous gluconate

• Ferrous fumarate

• Ferrous sulfate

In some cases, people need intravenous (IV) iron. This might be the case if someone's iron levels are extremely low, or if they're experiencing more severe symptoms. IV iron may also be better for someone who cannot take iron by mouth.

Response to iron therapy can be seen in as little as 2 weeks. But most people will need to continue taking iron supplements for several weeks or even a few months. Your healthcare team will monitor your treatment with blood work. Depending on the cause of your iron deficiency, you may be able to stop taking supplements once your blood counts and iron levels are normal.

How to take iron supplements

Oral iron supplements should be taken on an empty stomach, if possible. This is because there are some foods that may interfere with iron absorption. Iron should not be taken with:

• Milk

• Eggs

• High-fiber foods

• Tea or coffee

There's some data to support the idea that orange juice can actually increase iron absorption, so taking iron supplements with a glass of orange juice is OK.

Certain medications can also interfere with iron absorption such as:

• Antacids

• Calcium supplements

• Zinc supplements

• Proton pump inhibitors

• Levothyroxine

• Levodopa

People should take iron supplements either 2 hours before or 4 hours after taking these medications.

Side effects of iron supplements

Side effects of oral iron supplementation include:

• Abdominal discomfort

• Nausea

• Diarrhea

• Constipation

• Black, green, or tarry stools

Taking too much iron can cause mild to severe adverse effects - from nausea to multisystem organ failure, seizures, and even death. So it's important to always take iron supplements as prescribed. Talk with your healthcare team if you're having side effects from them.

Finally, it's important to note that fatal overdoses have been reported in children. Iron supplements should be safely stored so children cannot get ahold of them.

The role of iron-rich foods

While iron-rich foods are usually not enough to treat IDA, they can help prevent iron deficiency. Iron-rich foods include both animal and plant-based foods. But iron from animal-based food is more easily absorbed.

Examples of iron-rich foods include:

• Meat (especially organ meat, like liver)

• Eggs

• Seafood

• Raisins

• Prunes

• Spinach

• Broccoli

• Beans and lentils

• Fortified breads and cereals

What happens when iron-deficiency anemia isn't treated?

Iron plays a major role in many metabolic processes of the body. So the consequences of iron-deficiency anemia can be wide-ranging and include:

• Worsening heart disease

• Increased risk of infection

• Complications during pregnancy

• Physical and cognitive difficulties in children

• Restless leg syndrome

When to get emergency help

Most people with iron-deficiency anemia have very few or no symptoms. But if symptoms appear quickly, you should get emergency help right away. These symptoms include:

• A rapid heartbeat (over 100 beats per minute, even at rest)

• Intense dizziness

• Fainting

• Abnormal or heavy bleeding

• Chest pain

• Difficulty breathing

• Confusion or altered consciousness

Frequently asked questions