Are You Iron Deficient? 8 Things Women Should Know

Iron deficiency is the most common nutritional deficiency worldwide (particularly affecting women), and it's an easy one to miss. Many women brush off symptoms, such as fatigue, dizziness, and brain fog, maybe blaming poor sleep or a demanding job. There are no routine iron deficiency screening recommendations in the United States—if you go for an annual physical and don’t ask about it, your primary care provider may not include it in your blood work.

Sustained iron deficiency can lead to anemia, a more serious condition that can result in heart issues, as well as complications during pregnancy and in the postpartum period.

Regardless of whether it progresses to anemia, iron deficiency can leave some people feeling miserable.

“Women of reproductive age bear most of the burden of iron deficiency,” says Yale Medicine hematologist Layla Van Doren, MD, MBA. That’s because menstruation causes blood and iron loss, which men do not experience. Pregnancy, in particular, is a vulnerable time that increases the risk of iron deficiency. This is because much more iron is required during this period to support the developing fetus, she says. “Because we are not routinely screening for low iron, we don’t really know the true burden of iron deficiency for women going into pregnancy,” she adds.

Research estimates that up to one-third of women of reproductive age in the United States may not have enough iron in their bodies, Dr. Van Doren says. In 2023, a study, published in the Journal of the American Medical Association (JAMA), showed that almost 40% of females ages 12 to 21 years are iron deficient.

We asked Dr. Van Doren what women need to know about iron deficiency—and what to do if you develop iron-deficiency anemia.

Iron is a mineral that plays key roles in the body’s growth and development. It’s a building block in the formation of red blood cells, which carry oxygen from the lungs to the rest of the body. Red blood cells also transport carbon dioxide, a waste product released by the body’s tissues, back to the lungs to be exhaled.

Iron also contributes to healthy bone marrow, muscles, and organ function, as well as a healthy immune system. It is ingested through the gastrointestinal (GI) tract and then transferred to muscles for building red blood cells or stored for later use. What's more, iron plays a key role in every aspect of the body, since it is involved in DNA synthesis and repair.

Two proteins in the blood are important in measuring whether a person has enough iron. One is ferritin, which is the storage protein of iron. A blood test can show whether a person’s ferritin level is low, indicating iron deficiency. "A person is considered iron deficient if their ferritin level is less than 30 ng/mL [nanograms per millimeter of blood]," Dr. Van Doren says.

The other is hemoglobin, the iron-containing protein in red blood cells that delivers oxygen to the body’s tissues. A diagnosis of anemia is based on hemoglobin levels. According to World Health Organization (WHO) guidelines, less than 12 g/dL (grams per deciliter) of hemoglobin in the blood in women and less than 13 g/dL in men indicates that a person has anemia, Dr. Van Doren says.

Although, Dr. Van Doren notes, the use of sex-based hemoglobin or ferritin thresholds is controversial.

We all need a certain amount of iron—not too much or too little. How that applies to you depends on factors such as age, sex, and pregnancy status. Because the body does not make its own iron (although it does draw some from old red blood cells), people need to get iron from the food they eat, especially from iron-rich sources, such as red meat and leafy green vegetables.

According to federal recommendations, your stage in life determines how much iron you need to consume:

• Women ages 14 to 18: 15 milligrams a day
• Women ages 19 to 50: 18 milligrams a day
• Pregnant women: 27 milligrams a day
• Men of any age and women over 50: 8 milligrams a day

There are two kinds of iron in food that can be absorbed through the GI tract. The most readily absorbable is heme iron (the term is derived from the word “hemoglobin”), found in animal products. Non-heme iron, found in plants and iron-fortified foods, is less absorbable in the body, which is why vegetarians and vegans make up another group that is at risk for iron deficiency.

“But I don't tell patients just to go eat red meat, because that is associated with its own health problems,” Dr. Van Doren says. “There are many alternatives, such as chicken, fish, beans, legumes, and additional iron supplementation with iron pills.”

The U.S. government’s Dietary Guidelines for Americans provides a list of iron-rich foods.

Many of the symptoms of iron deficiency without anemia are “nonspecific and vague,” which can make them easy to disregard, Dr. Van Doren says.

Symptoms can include (but are not limited to):

• Fatigue, or always feeling tired, even after sleeping
• Hair thinning
• Thinning and brittle nails
• Restless legs
• Foggy thinking
• Poor mood

There are different causes of anemia, but iron deficiency is the leading one.

“When a person has anemia, the heart has to pump faster and harder to get that blood moving through the body to supply oxygen,” Dr. Van Doren says.

Some symptoms of anemia are the same as those of iron deficiency, while others are not. Symptoms of anemia include shortness of breath or chest pain, generalized weakness, and rapid heartbeat, among others. During pregnancy, anemia increases the risk of poorer outcomes for the mother and baby.

Menstruation is the primary reason why many more women than men are iron deficient. Women lose blood—and iron—every month when they menstruate. “The degree of iron deficiency depends on the amount of blood lost each month from menstruation,” Dr. Van Doren says.

About one in five women have heavy periods, which means they are especially at high risk for iron deficiency. Heavy menstrual bleeding is defined as 80 millimeters of blood loss per month OR excessive bleeding that interferes with a woman’s physical, emotional, and social material quality of life, Dr. Van Doren says. (Heavy bleeding is a reason to consult a doctor to make sure there isn’t an underlying cause that needs to be treated, she adds.) Fibroids, which are growths in the uterus that occur mostly in women in their 30s (although they can occur at any age), are a primary cause of heavy menstrual bleeding.

During pregnancy, the developing fetus also requires iron for fetal brain development. This means the iron requirement for women increases significantly during pregnancy. In fact, women need to maintain healthy iron levels throughout their lives, Dr. Van Doren says.

Case in point: Pregnant women should have healthy iron levels before they become pregnant. “If a woman begins pregnancy iron deficient, then it's going to be very difficult for her to make that up throughout her pregnancy,” Dr. Van Doren says. It’s especially important because taking iron pills to replenish iron levels can cause constipation, GI upset, and nausea—on top of the discomfort that pregnant women already have, she adds.

Depending on the severity of the deficiency, some people may be able to replenish their iron with iron pills. Because the body only absorbs small amounts of the iron a person consumes, bringing iron back to a healthy level can take months, with doctors monitoring the changing iron levels regularly.

“It's not fun to take oral iron,” Dr. Van Doren says. “A lot of people have GI upset, constipation, nausea, and dark stools.” She recommends taking iron pills every other day to lessen the risk of side effects.

But iron pills won’t work for everyone. “Sometimes, the amount of blood a person is losing is too great, and oral iron will never keep up with those losses,” Dr. Van Doren says. "The body must be able to process the iron, meaning the iron must be reduced by stomach acid to a form that can be absorbed in the GI tract. In these cases, patients may need intravenous [IV] iron, which can replenish iron levels more quickly. If someone has a problem absorbing oral iron, that is another indication for upfront IV iron."

Research is ongoing to determine which is more effective—oral or IV iron—particularly during pregnancy, Dr. Van Doren says. The latter restores iron levels more quickly than oral iron. But most primary care physicians start with oral iron, she adds. “If there is no improvement, they go to IV iron,” she says.

People with iron-deficiency anemia and severe symptoms may require a blood transfusion to replace lost red blood cells, but it is important to prevent it from getting to that point and to determine the cause of their anemia.

Routine screening for iron deficiency with and without anemia could lead to more women being diagnosed and treated, Dr. Van Doren says. Recognizing the burden of iron deficiency on quality of life and health outcomes, in 2023 the International Federation of Obstetrics and Gynecology recommended that all women and girls who menstruate should be screened regularly for iron deficiency.

However, the American College of Obstetrics and Gynecology recommends against routine testing for iron deficiency in pregnant women. In August 2024, the United States Preventive Services Task Force (USPSTF) issued a statement that also addressed iron screening in pregnant women, stating that “current evidence is insufficient to assess the balance of benefits and harms of screening for iron deficiency and iron-deficiency anemia in pregnant persons to prevent adverse maternal and infant health outcomes.”

“We need to gather more evidence,” Dr. Van Doren says. “We need to investigate the exact dangers of iron deficiency without anemia, and studies are ongoing to address this.” Questions still revolve around how iron deficiency impacts clinical outcomes and mortality.

The most important thing women can do is educate themselves about iron deficiency, ensure they are getting adequate iron in their diets, and talk to their doctors about any concerns they might have about the amount of blood they are losing every month through menstruation, Dr. Van Doren says.

“Women don’t always tell their physicians if they have symptoms of iron deficiency because they may think their symptoms are normal,” she adds. “I've had patients say, ‘All the women in my family have heavy bleeding.’ Maybe they've been told that their mother had heavy bleeding, so they assume it’s just normal for the family.”

Those conversations need to change—especially in the doctor’s office, she says. “I compare this to when you have fatigue and your doctor checks your thyroid hormone levels. Why not check iron? If you could know that your iron is low and you can fix it, why not do that? There’s no downside.”