Doru Paul, MD, is a board-certified oncologist and hematologist. He is an associate professor of clinical medicine at Weill Cornell Medical College.

Getting enough iron is essential. It helps you produce red blood cells—cells that carry oxygen from the lungs throughout the body—and supports your physical growth and brain development, per the Office of Dietary Supplements (ODS).

Iron deficiency means that the amount of iron in your body is low. This happens in about 4.5–18% of people in the US, per an August 2015 review published in the journal Lancet. Iron deficiency is more common among women and people who are pregnant.

You may have heard the term "anemia" used interchangeably with "iron deficiency," but the two can differ. Anemia is when the blood doesn't carry enough oxygen to the rest of the body, per the National Library of Medicine MedlinePlus resource.

Iron deficiency anemia (IDA) occurs when the iron deficiency is severe enough for a person to have fewer red blood cells, per an April 2018 paper published in Clinical Case Reports. It's the most common type of anemia.

Iron deficiency without anemia is challenging to diagnose since the red blood cell counts are normal in lab tests. But you may still experience symptoms such as weakness, fatigue, and difficulties concentrating, which can interfere with your work and daily life, per the April 2018 paper. If the deficiency progresses into IDA, the signs may become more severe.

The following symptoms are not unique to iron deficiency or IDA, but if you experience a combination of them, talk to your healthcare provider about getting your iron and red blood cell counts tested.

Fatigue is the most common symptom of iron deficiency. It's also a frequent symptom of IDA, appearing in about 44% of cases, per the August 2015 review.

Fatigue is an "unspecific" symptom, which means that people may feel fatigued due to a number of other conditions, such as a sleep disorder or celiac disease, per a January 2019 paper published in the journal Blood.

This symptom may be hard to detect, as people can get used to having busy lives and feeling tired. "They often just dismiss being tired as part of life," said Nancy Berliner, MD, deputy editor of Blood, the American Society of Hematology journal.

Iron deficiency causes less oxygen to reach your tissues, so your body is deprived of the energy it needs. If your fatigue comes with feeling weak, irritable, or unable to focus, a lack of iron might have something to do with it.

The number one cause of iron deficiency is heavy periods. A person may lose too much blood and not be able to replace all of it by their next period, according to Jacques Moritz, MD, director of gynecology at Mount Sinai St. Luke's Roosevelt in New York City.

An average person's period is about two to three tablespoons of blood each month, per the Office on Women's Health (OWH). Heavy bleeding means you change your tampon or pad every one to two hours, pass blood clots larger than quarters, or experience bleeding for more than eight days.

Heavy periods affect about one in five people who menstruate in the US annually and may happen naturally during your transition to menopause, per the OWH. But they're worth discussing with an OB-GYN as they can also signal issues with your thyroid or medication side effects.

Other causes of blood loss that may trigger an iron deficiency include pregnancy, regular blood donations, accidents, or surgeries, per the April 2018 paper.

You may look pale if your body has fewer red blood cells, which is what happens in anemia, per MedlinePlus. Paleness is not the same as loss of pigment (melanin) from the skin—it's related to blood flow instead.

The discoloration may show up inside of your lips, your gums, and the bottom eyelids. If they're less red than usual, low iron may be the cause.

Paleness is one of the top symptoms of IDA, appearing in about 45–50% of cases, per the August 2015 review.

If you suddenly become pale across your body or experience shortness of breath and bloody stools, contact your healthcare provider immediately, per MedlinePlus.

No matter how deeply you breathe, if your oxygen levels are low, you'll feel out of air, Dr. Berliner explained.

At first, you may feel short of breath more frequently when climbing a flight or stairs or completing your usual workout. Eventually, you may start getting breathless when resting, per the August 2015 review.

An overworked heart can have irregular heartbeats, heart murmurs, enlargement, and even heart failure. But for things to get that bad, your IDA would need to be undiagnosed or untreated for a while, per the National Heart, Lung, and Blood Institute (NHLBI).

If you have known heart disease, it's important to get your iron levels checked.

If you have a strong urge to move your legs, you may have restless leg syndrome (RLS), per MedlinePlus. IDA is one cause for the condition—RLS occurs in about 24% of cases.

Iron deficiency without anemia is mainly associated with RLS in people assigned female at birth, per an April 2020 study published in the journal Frontiers in Neurology. In people assigned male at birth who have iron deficiency without anemia, RLS is not common. If you fit this description and experience RLS, speak to your healthcare provider to rule out additional RLS causes.

An iron-deficient body will prioritize getting oxygen to your brain ahead of other tissues. But even then, your head will still get less oxygen than necessary, Dr. Berliner said. In response, the brain's arteries can swell, causing headaches, according to the National Headache Foundation.

Headaches are the most common symptoms of IDA, appearing in about 63% of cases, per the August 2015 review.

Pica is a condition in which a person wants to eat non-food or non-nutritional substances, such as ice, paper, clay, soil, glass, or sand. Pica is a way nutrient deficiency, most commonly iron deficiency, shows up in people, per a November 2017 paper published in the Journal of Medical Case Reports.

Acting on these cravings can lead to other health problems, including bowel obstruction and dental damage. If you experience pica, talk to your healthcare provider.

Iron deficiency can cause changes in the brain, raising the risk of psychological symptoms such as depression and anxiety, per a May 2020 study published in BMC Psychiatry.

It can also be a risk factor for sleep disorders. Fortunately, iron supplementation can reduce that risk.

When iron deficiency progresses into IDA, it can cause hair loss. "It sends your body into survival mode, so your body channels oxygen to support vital functions as opposed to ones like keeping your hair intact," Dr. Moritz explained.

Hair loss occurs in about 30% of IDA cases. Your hair may also appear dry and damaged, per the August 2015 review.

These symptoms happen because iron deficiency affects epithelial cells—cells that line your body's surfaces, such as skin, blood vessels, and organs, per MedlinePlus. Because of that, you may also experience dry and rough skin and brittle or spoon-shaped fingernails, per the August 2015 review.

Don't panic if a few hairs are in your drain, though. Most people lose about 50–100 hairs a day, per the American Academy of Dermatology. The main difference between hair shedding and hair loss is that, in the latter, the hair doesn't regrow until you address the cause of the loss.

Your thyroid makes hormones that control the rate of body activities, such as burning calories and heartbeat, per MedlinePlus. Iron deficiency can impair thyroid function, causing hypothyroidism (not making enough thyroid hormone), per a 2017 paper published in Acta Biomedica. Adding iron to your thyroid therapy can help with hypothyroidism treatment.

Hypothyroidism is often missed—up to 60% of people who have it don't know they do, according to the American Thyroid Association. Talk to your healthcare provider if you notice low energy levels, weight gain, or even a lower body temperature.

Embryos and fetuses require iron for development and can take iron from the pregnant person. Many people also lose a substantial amount of blood during delivery, which can lower iron counts, Dr. Moritz said.

If you're pregnant with multiples, have pregnancies close together, or regularly vomit because of morning sickness, talk to your healthcare provider to boost your iron intake potentially.

Besides sapping the color out of your tongue, IDA can reduce myoglobin levels, a protein in red blood cells that supports muscle health—like the muscle that makes up the tongue—Dr. Berliner said.

As a result, people who are iron deficient can experience an inflamed, shiny, or strangely smooth tongue. The tongue may also feel dry or sore. This condition is called glossitis, per StatPearls.

Celiac disease and inflammatory bowel diseases (IBDs) such as Crohn's disease and ulcerative colitis cause inflammation and damage to the digestive tract. This can lead to blood loss and problems absorbing iron, per the January 2019 paper.

In people with celiac disease, eating gluten may damage their small intestine, per MedlinePlus. IBDs cause inflammation in the gastrointestinal (GI) tract. Crohn's disease affects the entire GI tract, while ulcerative colitis only affects the colon, per MedlinePlus. IBDs present symptoms such as diarrhea, stomach pain, ulcers, and bleeding.

If you've been diagnosed with any of these GI conditions, talk to your healthcare provider about how you can increase your iron absorption.

Cold hands and feet can be symptoms of IDA, per the NHLBI. The body can have difficulty regulating temperature if it's not getting enough oxygen, per the ODS.

Iron intake recommendations vary by age and sex. People who are pregnant need more iron at any age, and people who are breastfeeding need less, per the NHLBI.

When it comes to iron, more isn't necessarily better. "While most [of] the attention is on iron deficiency, there is a concern as well for iron overload, which studies indicate can damage internal organs and may increase the risk of diabetes, heart attack, and cancer, particularly in older people," said nutritionist Rania Batayneh, author of The One One One Diet.

The best way to get to the recommended amount is through your diet. Iron-rich foods include beans, dried fruits, eggs, lean red meat, salmon, peas, tofu, and dark green leafy vegetables. You can also buy iron-fortified breads or cereals. Pair these with vitamin-C-rich foods such as oranges, strawberries, and tomatoes to help your body absorb iron, per the NHLBI.

Unless you have iron deficiency or IDA, you don't need to take supplements. Oral iron pills are reserved for treatment—which usually takes three to six months—or during pregnancy. They can come with side effects such as nausea, vomiting, and bad metallic taste, as well as digestive issues such as diarrhea or upset stomach, per the NHLBI. Additional treatment options are available. Talk to your healthcare provider about any new symptoms you experience.

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