Feeling so tired all the time? Iron deficiency might be the reason why.

From the outset, correcting an iron deficiency may seem small, but it can make a world of a difference in helping you feel empowered and in control of your health. Restoring iron to your body can help relieve depression, reduce migraines, improve stamina and boost energy.

Virtually every cell in the body requires iron in order to function well. Iron is involved in key bodily processes, including the transportation of oxygen in the blood. It also plays a central role in building energy and proteins, and it can be found in your red blood cells, bone marrow, muscles and the brain.

What causes iron deficiency, and why is it so important to treat it? Here’s what you need to know.

What causes low iron?

There are many reasons why iron deficiency could develop, and you can think of them as being split into two categories: “Either we aren't getting enough iron into our system, or we are losing it excessively above the rate at which our system can absorb it from food,” says Dr. Julia Cunningham, a benign hematologist with MedStar Georgetown University Hospital.

People who menstruate are naturally much more prone to developing iron deficiency and iron deficiency anemia, says Dr. Annette von Drygalski, a board-certified hematologist and director of the Center for Bleeding and Clotting Disorders at UC San Diego Health. In fact, recent research estimates 40% of girls and young women aged 12 to 21 in the US are affected by iron deficiency, with menstruation listed as the primary risk factor. Pregnancy and childbirth are other risk factors for iron deficiency, because the fetus will absorb a significant amount of iron in the body.

Any type of bleeding disorder, such as gastrointestinal bleeding, polyps and cancer, can aggravate iron deficiency, says von Drygalski. Other lesions that bleed, such as ulcers and hemorrhoids, can also contribute to iron depletion.

"Children can become iron deficient if they're not getting significant enough nutritional intake to keep up with their growth," adds Dr. Casey O’Connell, a hematologist and an associate professor of Clinical Medicine at Keck Medicine of the University of Southern California. As a child develops, the tissues grow and the number of blood cells expand. Consequently, more iron is needed.

Autoimmune diseases that affect the GI tract “can prevent a person from absorbing iron from the foods that they eat, even if they're eating iron-rich foods,” says Dr. Danielle Nance, a hematologist and co-director of the multidisciplinary programs at Banner MD Anderson Cancer Center.

Diet also has an important role to play in maintaining healthy levels of iron in the body. “Some people may eat a diet that has actually very little iron to be available for the body to absorb, and that can cause iron deficiency over long periods of time,” says Cunningham.

Good question: Ham is the centerpiece of many holiday meals. Is it good for you?

What are the symptoms of iron deficiency?

Weakness, fatigue and lightheadedness are among the most noticeable symptoms associated with iron deficiency, says Nance. Iron deficiency can also cause shortness of breath, and amplify the symptoms of any chronic condition, such as depression. It can also have an affect on your mood, ability to focus and sleep quality.

Iron deficiency anemia can intensify symptoms of fatigue and shortening of breath, and can cause cold sensitivity, hair loss, paleness to the skin and nail changes, says Cunningham. It has also been linked to restless leg syndrome, says von Drygalski.

It’s important to remember that “the signs and symptoms of iron deficiency and anemia are relatively non-specific,” adds Cunningham. The one telltale symptom of iron deficiency anemia that does not present in any other type of anemia is pica, which is a craving for non-food items (such as ice), she says.

Iron deficiency is also often an indication of another underlying health problem. For this reason, Cunningham emphasizes the importance of yearly blood panels that can help identify if your symptoms warrant further investigation.

Heads up: Depleted energy levels affect us all. But here's when they could indicate something serious.

How to fix low iron

There’s a few different routes that can be taken to restore healthy iron levels in the body. Choosing the right treatment will depend on the cause of the iron deficiency, and whether there are underlying illnesses at play, says Cunningham. For example, if someone is iron deficient and has no gastrointestinal problems (meaning they have no issues absorbing iron), taking oral iron tablets could be a great option, she says.

Constipation and an upset stomach are among the most common side effects associated with oral iron supplements, Cunningham says.

Whereas oral iron supplements could take upwards of six months to replenish someone’s iron levels, the results of IV iron are fairly instantaneous, says von Drygalski. If someone has heavy menstrual bleeding, or a gastrointestinal problem that would prevent them from absorbing iron correctly, IV iron is the more favorable option, she says.

If someone is severely iron deficient and anemic, and their hemoglobin is dangerously low, a blood transfusion may be needed. “But, we try to avoid that unless absolutely necessary,” O’Connell says.

When it comes to prevention, eating a well-balanced diet that incorporates iron-rich foods can lower your risk of developing iron deficiency. Because pregnancy and menstruation can take tremendous amounts of iron from the body, “women who are in their reproductive years should be eating extra foods with iron,” says Nance.

Additionally, despite misconceptions, vegetarians and vegans are not necessarily subject to iron deficiency, von Drygalski says. It's true that red meat is an excellent source of iron, but there are plenty of vegetarian sources of iron — think leafy green vegetables, beets, black beans and lentils, says Cunningham.

This article originally appeared on USA TODAY: What causes low iron? Symptoms and treatment options