Iron Deficiency in Female Athletes

Iron is a hot topic for athletes, particularly endurance athletes who have fatigue. “Fatigue doesn’t always mean iron deficiency,” says Adam Tenforde, MD, a Mass General Brigham sports medicine physician at Spaulding Rehabilitation Hospital. “But it’s usually the main symptom for low iron.”

But iron deficiency in women is not always straightforward to diagnose or treat. Dr. Tenforde, who has extensively researched iron and athletes, explains iron deficiency causes and effects. He also explains why you shouldn’t try to troubleshoot your iron levels on your own and offers tips for taking iron supplements.

Types of iron deficiency 

Iron is a mineral that’s essential for producing and maintaining healthy red blood cells. When your body doesn’t have enough iron, your red blood cells can’t carry as much oxygen as they should. Poor oxygen transport can make you feel tired and out of breath.

“It’s pretty alarming when a serious athlete gets tired just walking up the stairs,” says Dr. Tenforde. “But we see this in some athletes with undiagnosed iron deficiency.”

Iron deficiency can take different forms. The types typically seen in female athletes are:

• Iron deficiency anemia: This blood disorder is a common form of anemia. With this condition, your body can’t make enough hemoglobin (a protein in your red blood cells that transports oxygen) due to not having enough iron to make new red blood cells.
• Iron deficiency without anemia: Blood tests may show low ferritin (a protein that stores iron) but normal hemoglobin to indicate this condition. Persistent low iron stores may lead to iron deficiency anemia.

What causes iron deficiency in female athletes?

Many athletes don’t get enough iron in their diets, especially if they have dietary restrictions or don’t eat red meat.

“Some people don’t absorb iron well in the first place,” Dr. Tenforde says. “In addition, athletes don’t always choose to eat foods with high bioavailable iron.” Bioavailable means a substance is in a form your body can absorb and use.

“Other people don’t absorb iron well due to gastrointestinal problems,” he adds. Your body absorbs iron through your small intestine. So gut issues may prevent absorption of iron and other nutrients.

You also lose iron in a number of ways, according to Dr. Tenforde. These include:

• In your feces
• In your sweat
• Through blood loss during menstruation

How does iron deficiency affect athletic performance?

Low iron can seriously affect your energy levels and endurance. If your red blood cells aren’t healthy, your muscles don’t get enough oxygen. The effects on athletic performance depend on how iron deficient you are, what other conditions you have, and your level of fitness. 

How do you know if you have iron deficiency?

“Fatigue is the most common symptom, but a blood test is the only way to diagnose iron deficiency,” says Dr. Tenforde.

Tests for iron deficiency and anemia typically include:

• Complete blood count (CBC): Measures amounts of different components of your blood, including red blood cells and hemoglobin
• Iron panel: Measures different aspects of iron in your blood
• Serum ferritin: Measures the amount of ferritin in your bloodstream

But it’s not just a matter of looking at a few numbers in the blood test results, says Dr. Tenforde. Diagnosing iron deficiency can be tricky because ferritin levels may falsely test as normal, high, or low. There are many reasons for this. Illnesses and infection can cause temporarily elevated ferritin, for example. A normal ferritin level can falsely suggest ferritin is within a normal range—but this does not mean the ferritin level is appropriate for an athlete to feel well.

How much iron do females need?

People who are menstruating need 18 milligrams of iron per day, according to the National Institutes of Health. If you’re pregnant, breastfeeding, or post-menopausal, your needs will be different. And people who have iron deficiency need more iron than the standard recommended amount.

However, supplementing with iron isn’t something you should experiment with on your own.

“There are certain medical conditions, including hemochromatosis, that we need to consider before you begin any iron supplementation,” says Dr. Tenforde. Hemochromatosis causes toxic amounts of iron to build up in your body.

There are also other reasons to work with your health care provider while taking iron supplements. For example, too much iron can cause painful stomach cramps. “This is a tough one because some stomach discomfort with iron supplementation may actually be a good sign,” says Dr. Tenforde. “It means your small intestine is absorbing iron. But you shouldn’t be in extreme pain.”

Iron supplements for female athletes

You should take iron supplements only under the care of your provider. But if you do need to take iron, there are some common pitfalls to avoid. Here are tips for taking iron supplements:

• Avoid calcium-rich foods. Iron and calcium compete to be absorbed by your body. So, it’s best to avoid milk and other high-calcium foods when you take your iron supplement and for a couple of hours after.
• Avoid tea and coffee with your iron. Certain naturally occurring chemicals in tea and coffee may bind iron, which prevents your body from absorbing it.
• Take iron in the morning. Your body absorbs iron better earlier in the day.
• Take iron on an empty stomach. “Many people don’t want to do this because iron causes some stomach upset. But your body can’t absorb the iron if you take it with food,” says Dr. Tenforde.
• Take iron with an acidic drink or vitamin C. Your body can absorb iron better if you take it with something acidic such as orange juice or vitamin C.

How can you get more iron in your diet?

The most bioavailable source of iron is a molecule called heme that’s found in red meat, says Dr. Tenforde. Certain plant foods contain some iron, too. But it’s in a form your body doesn’t easily absorb.

“To prevent iron deficiency, a female athlete should eat a balanced diet that includes red meat,” says Dr. Tenforde. “But respecting individual personal beliefs and dietary preferences, that’s not always possible.”

He recommends that all athletes meet with a dietitian who specializes in sports nutrition. Even athletes who don’t have low iron can usually benefit from some tweaks to their diets.

If your iron is already low, you likely won’t be able to get enough iron from diet alone. You’ll need a supplement to get your levels back where they need to be.

“There are a number of different reasons to care about iron status,” says Dr. Tenforde. “It goes beyond performance and fatigue. It can also be a marker for overall health and wellbeing, and it prompts us to look at ways to improve nutrition.”

The Women’s Sports Medicine Program at Mass General Brigham provides services for athletes at all levels. In addition to treating injuries, sports dietitians on staff can help you navigate the nutritional demands of an active life.