Understanding Iron Deficiency

Experts explain why people may need more of this essential mineral at each life stage, how to recognize symptoms of iron deficiency, and ways to treat it.

Iron deficiency is a common condition — in the U.S., an estimated 10 million people lack this essential mineral, and two recent studies found that the condition affects more than a third of young women and women of reproductive age.

Iron is a building block for hemoglobin, a protein in red blood cells that delivers fresh oxygen to our organs, muscles, and tissues. It also helps process the food we eat, which we need for energy and healthy growth. When we don’t have sufficient iron, it changes how our body functions, leading to side effects like fatigue and dizziness. But in more serious cases, it can lead to iron deficiency anemia, a condition in which the blood doesn’t have enough red blood cells.

“Our red blood cells carry oxygen for us, and that’s why we can do everything that we do,” says NewYork-Presbyterian/Columbia Irving Medical Center hematologist Dr. Andrew Eisenberger, “If you don’t have iron in your body, then you can’t make red blood cells, and you become like a lump on the couch.”

Health Matters spoke to experts about what causes iron deficiency in different age groups, how to treat it, and why it may be overlooked and underdiagnosed.

Infants and Toddlers

Because food is a main source of iron, babies and toddlers can develop iron deficiency as their eating habits and exposure to new foods are still evolving. “By far, the leading cause of iron deficiency in young children is related to their diets,” says NewYork-Presbyterian/Weill Cornell Medical Center pediatrician Dr. Gopi Desai. “I tell parents to start working iron-rich foods into a child’s diet early. What’s often overlooked is that the eating habits you form in childhood really stick with you through older childhood and into adulthood.”

Dr. Gopi Desai

Dr. Gopi Desai

Pediatricians check iron levels with a blood test when children are one and two years of age. The most common symptoms of iron deficiency and anemia are fatigue and low energy. In more serious cases, anemia can cause developmental delays because not enough oxygen is reaching various parts of the body. Children may look pale, and their hands and feet might get colder than usual. Another side effect in older kids (typically over age 3) is pica, which is a craving for items with no nutritional value — for example ice, dirt, paper, or cardboard.

Treating iron deficiency in infants is easy — starting at four months of age, you can give iron-fortified formula or add drops of iron supplement to a bottle of breastmilk.

As children grow older, Dr. Desai recommends incorporating iron-rich foods in at least two meals per day. Meat, leafy greens (like spinach, collard greens, and kale), broccoli, shrimp, sardines, and sweet potatoes are good sources of iron. For pickier eaters, beans, lentils, chickpeas, and iron-fortified cereals or breads are good options. In addition, it’s important to limit cow’s milk to a maximum of 20 to 24 ounces daily because too much milk can prevent the body from absorbing iron.

If your child is still not getting enough iron, the pediatrician may recommend an iron supplement. However, the supplements have a metallic taste and can cause constipation, so kids may refuse to take them. “The ideal way to get iron is through foods rather than supplements,” says Dr. Desai. “Parents should just try their best. While kale is a great source of iron, for kids, it may start with chicken nuggets.”


As children enter puberty, iron deficiency is surprisingly common, especially among girls. The main driver is blood loss as a result of heavy or prolonged menstrual periods, but a large national study recently published in JAMA analyzed two decades of data from females aged 12 to 21, and roughly 27% of the young women with iron deficiency hadn’t had their first period.

Diagnosing iron deficiency among adolescents is a challenge because the symptoms — fatigue, headaches, irritability, and poor concentration — are common complaints from teens who may be staying up too late or have stress and anxiety at school. If symptoms persist, and especially if they are interfering with school or athletic performance, that is a sign to see a medical provider.

Dr. Jane Chang

In addition, there are no official guidelines from the American Academy of Pediatrics to regularly check for iron deficiency among this age group. Screening (a simple blood test for hemoglobin levels) is recommended for anemia every 5 to 10 years throughout childbearing years and annually if there are risk factors like abnormal periods, a low-iron diet, or a history of iron deficiency anemia.

“We know a significant number of young women have low iron but not are anemic,” says Dr. Jane Chang, an adolescent medicine specialist, associate attending pediatrician at NewYork-Presbyterian Komansky Children’s Hospital, and associate professor of clinical pediatrics at Weill Cornell Medicine. “We ask adolescents about their dietary intake and menstrual periods, but current screening guidance may miss individuals with iron deficiency.”

Because teens undergo rapid growth spurts, a diet with iron-rich foods (for example meat, seafood, leafy green vegetables, tofu, beans) is key to preventing iron deficiency. Dr. Chang also recommends a daily multivitamin for all her patients.

It is also extremely important for both teens and their caregivers to be open about menstruation, so young people report to the pediatrician when they have an abnormal period. If a new pad or tampon is needed every hour, or there is bleeding for more than seven days, that is excessive bleeding.

“We need to reduce the stigma and discomfort associated with talking about periods, so that teens can learn the range of what is considered normal,” says Dr. Chang. “I encourage my patients to track their periods in a notebook or an app on their phone and let their parent or provider know when something seems outside the realm of normal range.”

Pregnant People

During pregnancy, the baby absorbs iron through the mother’s bloodstream, and as the baby grows, the demand for iron increases. “A substantial amount of blood flows through the placenta and umbilical cord to the fetus, so pregnancy can lead to iron deficiency for the mother,” says Dr. Cassandra Blot Simmons, chief of the Division of General Obstetrics & Gynecology at NewYork-Presbyterian Westchester and NewYork-Presbyterian/Columbia University Irving Medical Center. “Hence the reason for early maternal screening and prenatal vitamins.”

At the first prenatal visit, the OB-GYN will screen for iron levels with a blood test to establish a baseline — at this point, it’s important to share any relevant medical history, like abnormal periods, family members who had anemia, or special diets. A pregnant person should have about 65 milligrams of elemental iron every day, according to Dr. Simmons, which most people can get with supplements along with plenty of iron-rich foods.

Dr. Cassandra Simmons

Dr. Cassandra Simmons

By the end of the second trimester, the mother’s blood volume doubles, so iron can become diluted. The OB-GYN will continue to screen for iron at 24 to 28 weeks and at the beginning of the ninth month. Says Dr. Simmons, “It’s also really important to monitor iron in the postpartum period after a normal delivery or cesarean section; nursing mothers provide iron through the breast milk.”

Among pregnant people, the most common symptoms of iron deficiency are lightheadedness and fatigue. However, if the iron deficiency is severe, it can affect the baby’s growth. The good news is that abnormalities are usually identified by an ultrasound and easily corrected by iron supplementation with oral vitamins, infusion, or diet. “Remember, a pregnant person requires energy and oxygen to support the process of growing a baby that begins as a cluster of cells and progresses to the size of a newborn over nine months,” says Dr. Simmons. “A large part of achieving a successful outcome for both the mom and baby requires the maintenance of a balanced diet, exercise, and mineral supplements to provide the body with the best opportunity for a healthy pregnancy.”

Older Adults

The vast majority of iron deficiency in people 50 or older is either from problems with absorbing iron or gastrointestinal bleeding. “A key point is that the body doesn’t lose iron naturally,” says Dr. Eisenberger. “Humans have about 4,000 to 5,000 milligrams of iron in them, and we’re actually hardwired to lose only one milligram a day.”

To diagnose iron deficiency, a primary care doctor or hematologist will first order a complete blood count (CBC) test, which shows whether someone is anemic. Many primary care providers will also check an iron level, but the results can be misleading. “The iron blood test basically tells me what was in your last meal,” says Dr. Eisenberger. “You could have tons of iron stored in your body, but if you’ve been fasting for 25 hours, the iron blood test may come back low. The most accurate is a ferritin test, which is a blood protein that contains iron. It gives us the most useful information.”

Dr. Andrew Eisenberger

If the ferritin test shows low iron levels, one question to examine is poor absorption, which may be a result of other health conditions. For example, the body needs acid to absorb iron, so people who take acid reflux medicine for years can end up with iron deficiency. In addition, people who have had weight loss surgery are also no longer able to absorb iron efficiently.

Another common scenario is blood loss in the gastrointestinal tract, which sometimes can be detected with a colonoscopy or an upper endoscopy. “A patient may not even notice blood in their stool, but a small amount of bleeding every day can lead to anemia,” says Dr. Eisenberger. “Whenever I see somebody over the age of 45, the first thing I ask is whether they’ve had a colonoscopy. In most cases, iron deficiency anemia is not from colon cancer. There are lots of places where you can lose blood from your gastrointestinal tract as you get older, so don’t panic.”

Through rare, bleeding related to cervical or uterine cancer could also lead to iron deficiency in postmenopausal women.

The symptoms of iron deficiency among older adults include fatigue and dizziness; pica (craving substances with no nutritional value, such as ice, dirt, or uncooked rice); leg cramps or restless leg syndrome at night; and mild hair loss.

While the most readily available and inexpensive treatment is an iron supplement, pills can cause bloating, nausea, and constipation. “I tell my patients to take iron pills once a day, three days a week at first, and then if they tolerate it, I have them take it daily,” says Dr. Eisenberger. “Taking iron three times a day is going to cause more side effects and doesn’t really improve iron absorption at all.”

For those who cannot tolerate iron supplements, another option is intravenous iron, which does not have the gastrointestinal side effects. An infusion of iron is given one or two times a year to get the blood counts back up to normal.

“A lot of people we see with iron deficiency have known it for a long time and they know it makes them feel terrible and exhausted, but they cannot tolerate iron pills,” says Dr. Eisenberger. “It’s important to see a hematologist, because iron deficiency is very easy to fix, and it really will tremendously improve your quality of life.”

At A Glance

Featured Experts


Consult an Expert

Find a Doctor or call