Iron deficiency is one of the most widespread nutritional problems around the world, affecting how your body produces healthy red blood cells and leaving you feeling exhausted, weak, and unable to keep up with daily life.

What is Iron Deficiency?

Iron deficiency happens when your body doesn’t have enough iron to function properly. This mineral is essential for making hemoglobin, which is a special protein inside your red blood cells that carries oxygen from your lungs to every part of your body. When you don’t have enough iron, your body struggles to make enough hemoglobin, and without adequate hemoglobin, your blood cannot transport sufficient oxygen to your tissues and organs.^[1]

Think of iron as fuel for your cells. Your body needs it to produce energy for daily activities, maintain a healthy immune system, support muscle function, and even keep your skin, hair, and nails in good condition. Iron also plays a role in making certain enzymes that help drive many important chemical reactions throughout your body.^[2]

Your body is quite clever about managing iron. It absorbs iron from the food you eat through cells lining your digestive tract, although only a small fraction of the iron you consume actually gets absorbed. Once in your bloodstream, a protein called transferrin attaches to the iron and delivers it to your liver, where it’s stored as ferritin. When your bone marrow needs to make new red blood cells, this stored iron is released and put to work. Even when red blood cells age and die after about 120 days in circulation, your spleen reabsorbs them and recycles their iron for future use.^[2]

Understanding Iron Deficiency Anemia

When iron deficiency becomes severe enough that your body cannot make sufficient red blood cells, you develop iron deficiency anemia. This is the most common form of anemia worldwide and represents the most severe stage of iron deficiency.^[1]

Iron deficiency anemia develops in three stages. In the first stage, your iron stores begin to decrease, but your red blood cells haven’t been affected yet. During the second stage, when iron stores become low, your body changes how it processes red blood cells, and your bone marrow starts making red blood cells without enough hemoglobin. By the third stage, hemoglobin drops below normal levels, and you begin to experience the symptoms of iron deficiency anemia.^[1]

How Common is Iron Deficiency?

Iron deficiency is extremely common, affecting approximately one-third of the world’s population. It’s the leading cause of anemia worldwide, responsible for about half of all anemia cases. Up to 5% of the Australian population is thought to have iron deficiency anemia.^[3]

The prevalence varies significantly by geography and demographics. In developing countries, between 30% and 70% of people have iron deficiency, while in high-income countries the rate is lower, around 20%, partly due to iron fortification of grain products. However, it’s important to note that only one-third to one-half of people with iron deficiency actually develop full-blown iron deficiency anemia.^[18]

Women are more commonly affected than men. In the United States, about 10% of women of childbearing age have iron deficiency, compared to only 1% of men under age 50. Among children, approximately 9% of those aged 12 to 36 months are iron deficient, and about one-third of these children develop anemia. Rates of iron deficiency increase with age in both sexes, with adults over 65 showing rates between 12% and 17%.^[4]

Menstruating women face greater risk than men and postmenopausal women because they lose iron regularly through menstruation. On average, a menstruating woman loses about 1 milligram of iron per cycle, though this can be as high as 5 milligrams or more if periods are heavy.^[18]

What Causes Iron Deficiency?

Iron deficiency can develop for several different reasons, and understanding the cause is essential for proper treatment. The main causes include insufficient iron intake, decreased absorption of iron, increased need for iron, and blood loss.^[6]

Blood loss is the most common cause of iron deficiency, particularly in older adults. This can happen through heavy menstrual periods in women, or from bleeding in the digestive system. Conditions that cause gastrointestinal bleeding include ulcers in the stomach or intestines, esophageal reflux disease, ulcerative colitis, Crohn’s disease, gastritis (inflammation of the stomach), hemorrhoids, and tumors in the digestive tract. Less common sources of blood loss include chronic nosebleeds, bleeding from the kidneys or bladder, and frequent blood donations.^[1][2]

Not getting enough iron from your diet can also lead to deficiency. Your body needs to absorb only a small amount of iron each day to stay healthy—around 1 milligram for adult males and 1.5 milligrams for menstruating females. However, because our bodies absorb only a fraction of the iron in food, we need to consume several times that amount. Vegetarians and vegans may be at higher risk because iron from plant sources, even iron-rich vegetables, is not absorbed as well as iron from meat, poultry, and fish.^[2][3]

Malabsorption, where iron can no longer be properly absorbed through your digestive system, is another important cause. This is more common in people with celiac disease, inflammatory bowel diseases, or those who have had weight loss surgery or gastric bypass operations. People taking anti-acid medications may also absorb less iron.^[1][2]

Sometimes the body simply needs more iron than usual. During pregnancy, your body needs twice the normal amount of iron to support the growing baby, placenta, and increased blood volume. Infants, children, and teenagers also need extra iron during periods of rapid growth. Breastfeeding mothers require additional iron as well.^[4][6]

In developing countries, parasitic infestations are a significant cause of iron deficiency. Additionally, vigorous exercise, particularly long-distance running, can sometimes cause a condition called “march hematuria” where trauma to small blood vessels in the feet leads to blood loss and iron loss through urine.^[2][4]

Who is at Risk?

Certain groups of people face higher chances of developing iron deficiency. Women who menstruate are at increased risk, especially if they have heavy periods. The risk is even greater for women who are pregnant, have recently given birth, or are breastfeeding because their bodies need extra iron during these times.^[1][2]

People who have undergone major surgery, particularly gastrointestinal or weight loss surgery, face elevated risk. Those who donate blood frequently may also deplete their iron stores over time. Children between 12 and 36 months of age are vulnerable, as are adolescents going through growth spurts. Older adults over 65 also have higher rates of iron deficiency.^[1][4]

Anyone with digestive system diseases is more likely to develop iron deficiency. These conditions include celiac disease, inflammatory bowel diseases like ulcerative colitis or Crohn’s disease, and peptic ulcer disease. People taking medications that reduce stomach acid are also at increased risk.^[2]

Vegetarians and vegans need to pay special attention to their iron intake since plant-based iron is harder for the body to absorb. People infected with Helicobacter pylori bacteria may develop iron deficiency because this bacterium competes with the body for iron and reduces vitamin C in gastric secretions, which is needed for iron absorption.^[2][18]

Low-income families are particularly vulnerable to iron deficiency, as they may have less access to iron-rich foods. In developing nations, lack of access to nutritious food and parasitic infections significantly increase the risk.^[4]

Symptoms of Iron Deficiency

The symptoms of iron deficiency typically develop gradually and can be quite subtle at first. You might not even realize something is wrong until the deficiency becomes more severe. The most common symptom is fatigue—a persistent feeling of being tired and lacking energy that doesn’t improve with rest.^[1]

Many people with iron deficiency experience weakness and find it difficult to complete everyday tasks. You might feel short of breath or notice your heart racing, especially during physical activity. Some people develop headaches, feel dizzy or lightheaded, or notice they become irritable more easily.^[1][2]

Physical changes can also occur. Your skin may appear pale or take on a yellowish, sallow color. Your hands and feet might feel unusually cold. Some people notice their tongue becomes sore or smooth, or they develop muscle cramps.^[1][2]

One peculiar symptom is pica—developing cravings for non-food items such as ice, dirt, clay, paint, chalk, or paper. Another unusual sign is koilonychia, where fingernails and toenails become thin, brittle, and develop a spoon-like shape. Hair loss, poor sleep, and cold intolerance can also occur.^[1][2]

In children, iron deficiency can lead to developmental delays and behavioral problems, decreased appetite, and poor performance at school. Young children may become more irritable and have difficulty concentrating.^[6][18]

Some people experience what sounds like pounding or “whooshing” in their ears. Others develop restless legs syndrome, where they feel an uncomfortable urge to move their legs, especially at night.^[2]

Prevention of Iron Deficiency

Preventing iron deficiency starts with eating a balanced diet that includes good sources of iron. The best dietary sources include red meat, poultry, and fish, which contain a type of iron called heme iron that your body absorbs easily. Plant sources like green leafy vegetables, beans, lentils, iron-fortified cereals and bread also provide iron, though in a form called non-heme iron that is harder for your body to absorb.^[2][3]

You can help your body absorb more iron by eating vitamin C-rich foods along with iron-containing meals. Oranges, lemons, tomatoes, berries, and other foods high in vitamin C enhance iron absorption. This is why healthcare providers often recommend taking iron supplements with a glass of orange juice or a vitamin C pill.^[5]

Some foods and drinks can actually block iron absorption and should be consumed separately from iron-rich meals. Tea, coffee, and foods high in compounds called polyphenols—such as dark chocolate, red wine, and green tea—can bind to iron and prevent your body from absorbing it. If you have iron deficiency, try to consume these items at least two hours away from meals containing iron or iron supplements.^[19]

For babies, breastfeeding for the first year of life helps prevent iron deficiency because breast milk contains iron in a highly absorbable form. If breastfeeding isn’t possible, using iron-fortified formula is important. Babies should not be given cow’s milk during their first year, as it contains little iron and can interfere with iron absorption.^[2][4]

During pregnancy, women should follow their healthcare provider’s recommendations about iron supplementation, as their bodies need significantly more iron. Women with heavy menstrual periods should talk to their doctor about ways to reduce blood loss or take iron supplements to replace what’s lost.^[1]

Regular health screenings can help catch iron deficiency early. All pregnant women should be screened for iron deficiency, and children should be screened at one year of age. People with conditions that put them at high risk, such as celiac disease or inflammatory bowel disease, should have their iron levels monitored regularly.^[9]

How Iron Deficiency Affects Your Body

Understanding what happens inside your body when iron levels drop helps explain why the symptoms occur. Iron is crucial for making hemoglobin, and hemoglobin accounts for about two-thirds of all the iron in your body. When iron becomes scarce, your bone marrow cannot produce enough hemoglobin, so the red blood cells it makes are smaller than normal and contain less of the oxygen-carrying protein.^[2][3]

These smaller, paler red blood cells cannot carry as much oxygen to your tissues and organs. Your muscles need oxygen to work properly, which is why people with iron deficiency feel weak and tire easily. Your brain is especially sensitive to oxygen levels, so when oxygen delivery drops, you might experience difficulty concentrating, memory problems, headaches, and what some people call “brain fog.”^[1]

Iron is also a key component of myoglobin, a special protein that stores oxygen in muscle cells. Without adequate iron, your muscles cannot store enough oxygen, which affects your strength and endurance. This is why even mild physical activity can leave you breathless and exhausted when you’re iron deficient.^[3]

Many enzymes throughout your body contain iron, including those involved in producing energy. When iron is low, these enzymes cannot function efficiently, further contributing to fatigue. Your immune system also depends on adequate iron to function properly, which may explain why people with iron deficiency seem to get sick more often.^[3]

When your body senses low oxygen levels in the blood, your heart tries to compensate by beating faster to circulate more blood. This is why many people with iron deficiency experience a rapid heartbeat or feel their heart pounding. Over time, if left untreated, severe iron deficiency anemia can strain the heart, potentially leading to an enlarged heart or even heart failure.^[1]

In children, iron deficiency during critical periods of growth and brain development can have lasting effects. The brain needs iron for proper development and function, so iron deficiency in young children can lead to developmental delays, learning difficulties, and behavioral problems that may persist even after iron levels are corrected.^[1][18]

Your body tries to adapt to low iron levels by absorbing more iron from food and using stored iron more efficiently. However, when iron stores in the liver, spleen, and bone marrow become depleted, these compensatory mechanisms fail, and symptoms become more noticeable. The body prioritizes iron for essential functions like making red blood cells, which means less important tissues like skin, hair, and nails may show signs of deficiency first.^[3]

Iron loss continues every day through normal processes like shedding intestinal cells, sweating, and in women, menstruation. The average person needs to absorb around 1 to 1.5 milligrams of iron daily just to replace these losses. When intake or absorption cannot keep pace with losses, iron deficiency develops progressively over weeks or months.^[3]