Josie Riggs ran track at Southern Utah University, specializing in the mile and the 5K. That’s when she first discovered that something wasn’t quite right.

She started feeling lightheaded and dizzy, especially when standing up after tying her shoes. She thought this was weird, but brushed it off. Then she began experiencing an extreme fatigue she couldn’t ignore. She finished last in all of her races.

“I would push as hard as I possibly could, but my body simply couldn’t hit the paces I’d previously been able to hit without a problem,” Riggs says.

After a few months of this deep fatigue, she went to the doctor and got a blood test, which confirmed that her symptoms were the result of low iron levels.

Rigg’s story is not rare. In fact, she’s part of the 35 percent of women under 50 in the U.S. who are iron deficient.

Blood work can help solve the puzzle of why you feel crummy, and what to do about it: Iron deficiency is when the body lacks enough iron to create healthy, red blood cells. Without iron, the body can’t produce hemoglobin, a component in cells that transports oxygen throughout the body. When you run, your muscles require oxygen, and if your body can’t keep up with the demand, you may experience symptoms like fatigue, decreased endurance, and impaired performance.

Even if your blood work comes back within the “normal” range, your iron may be below optimal levels for peak performance.

“Iron deficiency is the first step on a spectrum. People can be iron deficient without being anemic, and the goal is to find those people early on, because it’s a lot easier to deal with at the onset,” says Dr. Ted Farrar, who has 28 years of experience in family medicine. He’s also the Sports Medicine Fellowship Director at The University of South Florida and an Ironman triathlete and runner.

Farrar confirms that within the general population of adolescent women, 17 percent are iron deficient and 6 percent have iron deficiency anemia. For those over 21, the percentages are 12 percent and 4 percent, respectively. But for female athletes, nearly one third have some level of iron deficiency.

“With athletes, it’s 15 percent to35 percent, which is a crazy range, so we start asking, ‘why does this happen?’ One reason is because of higher iron turnover and greater iron needs,” he says.

Who’s At Risk

It’s important to note that, even though women are more likely to be iron deficient, men can be, too. Studies show that 11 percent of male endurance athletes are iron deficient.

Iron deficiency is common among endurance athletes for a few reasons. Endurance training stimulates the creation of red blood cells, and iron is crucial to the production of hemoglobin, the protein in red blood cells that carries oxygen throughout the body. If the increased demand for iron isn’t met, the body can become iron deficient, leading to symptoms such as chronic fatigue, decreased endurance, and weakness.

Another reason why endurance athletes are more likely to be iron deficient is because runners have higher iron requirements than the average person due to a condition called foot strike hemolysis. “The repetitive pounding of the foot against the ground causes microvascular trauma that destroys red blood cells,” Dr. Farrar says. “So if you’re running 20 to30 miles a week, you would have a lot more iron turnover than a swimmer or cyclist.”

Studies show that exercise-induced iron deficiency anemia is found mostly in athletes with heavy training loads, like middle to long distance runners.

Women are disproportionately affected by iron deficiency due to blood loss from menstruation. Among reproductive aged women in the US, 20 percent have iron deficiency and 38-39 percent have iron deficiency anemia.

Also, women are more likely to have a diet low in iron, as there are more women than men who are vegan or vegetarian. Dietary iron comes from two sources: heme and non-heme. Heme includes animal sources like beef, eggs, oysters, tuna, salmon, and liver. Non-heme includes non-animal sources like nuts and seeds, beans and legumes, dark leafy vegetables, broccoli, peas, and dried fruit. Iron from heme sources has a 30 percent absorption rate, while non-heme sources are only 10 percent. Therefore, if you eat a vegan or vegetarian diet, it’s important to track your dietary iron intake.

Restrictive eating also can increase your risk of becoming iron deficient. One study found that 39 percent of those with anorexia nervosa are diagnosed with anemia. Depriving yourself of food can lead to being deficient in all kinds of nutrients—not just iron.

In addition, conditions like Crohn’s disease, Celiac disease, stomach ulcers, fibroids, and pregnancy can increase your risk for iron deficiency.

 Reading the Signs

One reason iron deficiency in female athletes may be overlooked is because the symptoms are wide-ranging and similar to other conditions. Chronic fatigue, weakness, headaches, and dizziness are symptoms of iron deficiency, but they can also be related to overtraining and/or undereating.

Sometimes, like in the case of Riggs, the onset of symptoms is so insidious that you normalize them. You may not realize you feel different, or may attribute the feelings to life stress or simply being in your head.

“Oftentimes, an athlete isn’t even in a doctor’s office until after many of the symptoms show up,” Farrar says.

Other symptoms include shortness of breath, trouble concentrating, restless legs, and brittle hair, skin, and nails, as well as a condition called pica, or cravings for non-food substances like ice, dirt, and paper.

If you’re experiencing any of these symptoms, it may be time to order a blood test. There is only upside to getting a complete blood count (CBC), which measures red blood cells, white blood cells, hemoglobin, hematocrit, and platelets. And make sure to ask for an additional ferritin test. In fact, many sports medicine professionals recommend getting this type of blood work once a year.

“One thing female endurance athletes can do is ask their family doctor or Ob/Gyn to run a CBC with ferritin once a year,” Farrar says. “Especially if they’ve ever had iron deficiency or have any risk factors like fibroids, heavy periods, or if they’re a vegetarian.”

Diagnosing Iron Deficiency 

To test for iron deficiency, your doctor will order a CBC test, which will include values for hemoglobin and hematocrit. They may also test ferritin, iron binding capacity, and total iron.

Standard ferritin range:

– 30-200 ng/dL for women

– 30-300 ng/dL for men

Standard hemoglobin range:

– 12-15 g/dL for women

– 13-16.5 g/dL for men

*Ranges may vary by laboratory and method of measurement  

“A ferritin level under 15 ng/dL is definitely a problem,” Farrar says. “For those ladies, we’d also look at hemoglobin to see if they’re anemic.”

Iron deficiency is when the body lacks enough iron to meet demand, whether that’s due to low dietary intake, poor absorption, blood loss, or increased iron needs. Whereas iron deficiency anemia is a condition characterized by a deficiency of red blood cells or hemoglobin, which leads to decreased oxygen-carrying capacity. Iron deficiency is one of the most common causes of anemia, but there are others, such as chronic disease and genetic disorders.

Ferritin is a protein that stores iron, so a low value can indicate iron deficiency. However, low ferritin isn’t enough information to diagnose low iron; you also need to know why. That’s why your doctor might look at other values, like iron binding capacity, which is your body’s ability to take in more iron.

While these are the standard ranges, an endurance athlete, who is losing iron more quickly than they can replenish, shouldn’t be at the lower range of ferritin or hemoglobin. While those numbers may be considered “normal” for a non-athlete, it’s important to consider how you feel and how much activity you do. If your symptoms mimic iron deficiency, your ferritin or hemoglobin levels are on the lower side of the standard ranges, and your doctor won’t take your endurance training into account, it may be time to seek out a sports medicine specialist.

Taking an iron supplement will help if you’re not getting enough iron in your diet, but it won’t help if your body isn’t absorbing iron for some reason, such as a gastrointestinal issue. That’s why it’s important to get a blood test before starting an iron supplement.

“The dirty little secret of supplementing with iron is that you have to be careful of iron overload,” Farrar says. “Bad performance is one thing, but liver damage is another.”

How to Increase Your Iron Levels

The recommended, daily, dietary allowance for iron, in adults 19 to 50 years of age, is 8 mg for men and 18 mg for women. However, the U.S. military recommends 22 mg for female recruits, and Farrar says that’s a good recommendation for female athletes as well. Studies have shown that endurance athletes may need up to 70 percent more dietary iron than the daily recommended dosage.

For those who don’t get enough iron in their diet, taking an iron supplement may help. Ferrous fumarate and ferrous sulfate are two options that are generally easy on the stomach. Farrar says the best protocol for maximum absorption is to take an iron pill once every other day.

“Take your iron pill in the morning on an empty stomach with a glass of orange juice,” Farrar suggests. “Don’t drink tea, coffee, or milk together, or one hour before or after, taking iron. Also, avoid taking antacids with iron.”

Sometimes, a person’s iron levels are too low for supplementation to help. In this case, an intravenous iron infusion might be necessary. “Know that it takes about eight weeks for iron deficiency anemia to improve,” Farrar says.

For Riggs, it took a liquid iron supplement and an entire track season before she started feeling like herself again. Now, as a registered nurse and mom to two young boys, she wants to spread awareness about this deficiency commonly found among female endurance athletes so that runners can get back to performing at their best. “We need to be vigilant in watching for signs and symptoms,” she says. Riggs recently completed the Eugene Marathon, finishing in two hours, forty-nine minutes, and fifty-eight seconds as the 6th overall woman.