Iron Deficiency in Runners: Symptoms, Ferritin Levels, and Treatment

You’ve taken days off, you’re following a smart training plan, but you just can’t shake the lead from your legs or the sluggishness from your mind and body. It’s frustrating and feels beyond logic, till you talk to a few other female friends who say they were feeling the same way and found out the cause was low iron stores or runner’s anemia.

Well-known sports nutritionist Nancy Clark predicts nearly 50% of women are deficient, and it’s severely affecting their performance.

But what exactly is runner’s anemia? And why are runners so prone to it?

In this article, you’ll learn exactly that, as well as how to get tested to check if low iron levels are what’s causing all the fatigue you’ve been experiencing, and how to treat runner’s anemia.

Iron Deficiency in Runners

Iron deficiency is one of the most common nutritional issues among runners, particularly women and endurance athletes.

Symptoms often include unusual fatigue, heavy legs, slower paces, poor recovery, and a higher heart rate during easy runs. The good news is that blood work can identify the problem and, with the right treatment, most runners return to normal training.

What are the Causes of Runner’s Anemia?

Why are runners so susceptible to low iron? Usually, it’s a combination of factors that creates a perfect storm.

• Intense workouts can cause iron loss through sweat
• Intense workouts can decrease iron absorption as our digestion shuts down
• Foot strikes can break red blood cells, which is called foot strike hemolysis
• The body requires more oxygen to recover after workouts
• Lack of appropriate nutrients in the diet

What Does Iron Do For Us?

Think of iron as the fuel, hemoglobin as the delivery truck, and ferritin as your storage tank. You might still have enough delivery trucks (normal hemoglobin), but if the storage tank is nearly empty (low ferritin), performance can begin to suffer.

The body requires iron to transport oxygen from the lungs throughout the body and to muscle tissue, which uses oxygen to create energy. Without adequate iron stores, athletes’ performance suffers.

Males need about 8 mg/day and females need 18 mg/day.

While iron isn’t difficult to find in the diet – both from animal and plant sources, iron deficiency remains the most common nutrient deficiency worldwide.

Certain populations are at a higher risk of deficiency, including women of childbearing age (who lose iron during menstruation) and vegans and vegetarians who do not eat a balanced diet.

Symptoms of Runner’s Anemia

The first sign most runners notice is persistent fatigue.

Caffeine and rest are ineffective when a person is iron-deficient, as neither provides the cellular energy boost that iron does. Physicians describe it as ‘lethargy’.

Runners may misinterpret it as a lack of motivation, particularly in long-distance and endurance runners.

Other symptoms may occur if a runner is iron-depleted and has low ferritin levels. Low ferritin levels may lead to elevated blood lactate levels.

Additionally, it causes a runner’s legs to feel heavy, hinders their recovery from training and injuries, and leads to tight muscles.

Just as with iron deficiency, low ferritin levels also cause exhaustion and reduced motivation. These factors contribute to decreased performance in runners and an increased risk of overuse injuries, such as shin splints or stress fractures.

As someone who has dealt with low ferritin for many years, Coach Amanda can tell you that it often means months of great training and then suddenly weeks of absolute fatigue. It’s impossible to continue training at a high level, which means you’ll never get the consistent build you are looking for.

Anemia may have a detrimental effect on more than just a runner’s energy levels. It can deplete an individual’s ATP, the chemical that enables cells to function properly.

Additionally, it can be detrimental to heart health by lowering a person’s VO2 Max, the amount of oxygen the body uses during activity.

A high VO2 Max level suggests that the body utilizes oxygen efficiently. This is made more difficult by anemia.

Additionally, persistent anemia can result in thyroid health problems, which can throw a runner’s hormone levels off balance.

When Should I Ask for Blood Work?

It may look a little different for everyone, but these are the most common symptoms of runner’s anemia:

• Persistent fatigue that doesn’t go away even after a rest day or good night’s sleep

• Heavy legs that feel like lead, even on an easy/recovery run

• Unexplained pace decline where your typical paces feel much harder to hit

• Elevated heart rate that creeps higher than normal for the same kind of effort

• Poor recovery leaving you feeling wrecked after workouts that you used to bounce back quickly

• Frequent illness that’s constantly interrupting your schedule because your immune system is weak

• Dizziness, especially when standing up quickly or a hard workout

Of course, many of these can be symptoms of overtraining as well. Which is why this next section is so key.

How to Get Your Iron Levels Checked

One great tool for runners is your annual free physical. Most insurance plans provide this, and it allows you to get your blood work done, but you can also do more with other blood tests, like I detailed here>>

A good test will look at:

• hemoglobin (Hg),
• hematocrit (Hct),
• iron (Fe)
• total iron-binding capacity (TIBC)
• ferritin level

Anemia is low hemoglobin and hematocrit, while iron deficiency is low iron, high total iron-binding capacity, and low ferritin levels which is a measure of your iron stores.

If you’re looking to request basic blood tests, but aren’t sure what they’re called, I’ve got you covered. You will need to request two separate tests:

1. A ‘CBC,’ which stands for complete blood count
2. A serum ferritin test.

Again, start with an Everylywell at-home blood test, and you’ll also learn about any related mineral deficiencies that could be contributing to your fatigue.

Complete blood counts include an entire panel of tests, but the one that matters to you is your hemoglobin level.  Hemoglobin levels are expressed in grams per deciliter (g/dL) or, occasionally, grams per liter (g/L), which is just g/dL multiplied by 10.

A serum ferritin test is measured in ng/mL. A ferritin test requires a separate blood sample; the result is your serum ferritin level, which is commonly expressed in nanograms per milliliter, or ng/mL.

Additionally, you may see it expressed as micrograms per deciliter or g/dL, but don’t let that confuse you since both quantities are identical.

In most cases, a ferritin level below 30 ng/ml in women and 40 ng/ml in men will start affecting your running performance. Personally, I’ve been under 30 for years and attempting to fix it with food unsuccessfully, so I’ll share more on iron supplements for runners below.

What Ferritin Level Should Runners Have?

Things can get a little confusing here because “normal” on a standard lab report and “normal for a runner” aren’t always the same thing.

Most labs will only flag you as deficient once your ferritin drops below about 30ng/mL for women or 40 ng/mL for men. But those cutoffs were made for the general population, not runners putting in the training. Dietitian Kylee Van Horn breaks it down really well below, and it’s a great visual to keep in mind.

Basically, just barely squeaking above deficient isn’t really the goal. If your number is in the 20s or 30s and you’re still dragging through runs, it’s worth asking your doctor whether you should aim higher instead of settling for technically “normal”.

• New Sept 2026 guidelines stated that below 30 is too low for all adults, including menstruating women
• We still want to see runners at above 50+
• Many runners will feel best when they are 100+

Like many things use symptoms to help guide your next steps with the Dr instead of relying on a normal number.

How to Treat Runners’ Anemia

As you can see, the odds are stacked against you as a runner when it comes to maintaining your iron levels.

For this reason, it’s important to carefully monitor your iron levels over time and adjust your iron intake through diet or supplements if you find that your iron levels are low.

Let’s look at both these options and understand them further.

1. Iron-rich Foods

Ideally we want to start with food before supplementing. Iron is NOT something to supplement without doing bloodwork.

Here are some good sources of iron:

• Lean meat (organ meats are the gold standard)
• oysters
• egg yolk
• dark green leafy vegetables
• legumes
• dried fruit
• whole-grain or enriched cereals, bread

If you are concerned about your iron levels, there are foods that will decrease absorption.

Avoid these iron depleting foods

To be clear you can enjoy these foods, but not within a couple hours of your iron focused meal or supplement.

• coffee, tea
• milk, cheese (yup calcium decreases absorption)
• brown rice
• grapes and corn
• eggs

Additionally, you should consume vitamin C along with iron-rich meals to help with absorption.

Red meat is one of the best sources of iron, so meats such as beef, lamb, veal, and pork are all packed with iron. In fact, the redder the meat, the higher it is in iron.

But don’t go piling your plate with red meat just yet! We know there are benefits to reducing red meat consumption (you don’t have to give it up entirely if you don’t want to, but daily is going to lead to a different set of problems).

Whitney English an MS, RDN, CPT is going to give us some great tips on getting iron through plant-based sources!

2. Include A Lot of Plant-Based Iron Sources

While plants are rich sources of iron, they contain a form of iron that is not as readily absorbed in the body as the iron found in animals.

However, with a carefully planned diet and by keeping in mind a few beneficial tips to increase bioavailability, a plant-based diet can easily meet a person’s daily requirement for this vital nutrient.

Here are some of the top plant-based sources iron:

• Soybeans, cooked (1 cup): 8.8 mg
• Blackstrap molasses (2 T.): 7.2 mg
• Lentils, cooked (1 cup): 6.6 mg
• Tofu (1/2 cup): 6.6 mg
• Swiss Chard, cooked (1 cup): 4 mg
• White Beans (1/2 cup): 3.3 mg
• Tahini (2 T.): 2.7 mg
• Cashews (1 oz): 1.9 mg
• Baked Potato with Skin: 1.8 mg
• Quinoa (1/2 cup): 1.4 mg
• Kale, cooked (1 cup): 1.2 mg
• Raisins (1.5 oz): 0.8 mg

Consuming plant-based sources of iron with a source of vitamin C helps increase the absorption of iron. Vitamin C rich foods include citrus, strawberries, red peppers, and leafy greens.

Additionally, choosing iron sources that are lower in “anti-nutrients” like phytic acid and oxalates, which can bind iron and prevent its absorption, will help increase iron bioavailability.

Spinach for example is rich in iron but its high oxalate content makes it a poor source. To reduce the phytic acid in iron-rich foods like beans, soaking, sprouting, and cooking is recommended.

Enjoy a Power Bowl packed with quinoa, lentils, and cooked kale with some fresh sliced red bell peppers and you’ve got an iron-packed meal perfect for fueling your fitness!

3. Iron Supplements for Runners

Taking an iron supplement is a good idea for runners with low iron or ferritin levels to help give it a boost, while you work on food.

When buying an iron supplement, verify that it is in the form of ferrous (ferrous fumarate, ferrous sulfate, or ferrous gluconate). Iron can be taken in pill or liquid form, whichever is more convenient for you.

• Floradix is the Vegetarian liquid supplement that many like because it’s easy on the stomach. I liked it, but found that type of iron wasn’t helping my ferritin.
• Nature’s Made liquid is another non-plant based option. Liquid can be easier to absorb for some.
• Thorne is a brand I recommend for any supplement due to the high quality levels. This is a pill form at 25mg.

When to Take Iron Supplements as Runners

• It’s often recommended to take your iron supplement before bed.  Iron supplementation can occasionally cause mild stomach discomfort and gas. If you take them at night, you are unlikely to experience any discomfort.
• HOWEVER, a new study showed you could take it within 30 minutes of finishing your run to really optimize absorption. I did this for awhile and had no stomach issues with the things listed above.
• Remember to avoid calcium one hour before and one hour after you take your iron.
• Take iron supplements with vitamin C, such as a vitamin C supplement (Emergen C was my easy go to) or orange juice, as well as a b-complex supplement, to assist with absorption.
•  Consistency is key to see results.

If you’re simply trying to maintain your iron levels, 30mg is enough. If you have been diagnosed with iron deficiency, supplement with 60mg but remember to always consult with your doctor first.

4. Iron IV Infusion

Our final option is going to involve medical intervention. As noted after years of not seeing any changes in my ferritin (don’t be like me and wait so long), I decided to try this out.

Many, many of my female running friends have done these IV’s in the past. I was however still nervous. There is a lot of talk about iron pills making the stomach hurt and I thought that could happen here too.

Nope.

• You’ll get a blood test to see how low you are
• Go in to a comfy room and an IV bag will be attached with saline and iron
• You will likely need to go in once a week for a few weeks to get enough
• It usually takes a couple of weeks to fully see results

How long will it last? That seems to be the big hairy question no one can answer. For some folks this seems to flip the switch and get things back in order, so they can just supplement and stay at a good level. Others have gut issues that are limiting absorption and need to go in occasionally for another IV.

I have had 3 doses and I’m currently waiting to see what the results are! So I’ll be updating this soon.

Can Your Iron Levels Be Too High?

Yes. In addition to the problems of iron deficiency, distance runners also need to be aware of iron overload.  Iron overload can result in major health problems. This is why you should NOT supplement without getting tested first.

Iron is unique among minerals and vitamins in that the human body does not have a built-in, automatic system for removing it unless you bleed often.

Iron supplementation in individuals who already have enough iron storage can induce symptoms such as vomiting, diarrhea, and stomach discomfort. These symptoms can proceed to hemochromatosis, a systemic condition caused by iron overload and also liver failure.

Iron, rather than being an antioxidant, is a pro-oxidant, meaning it damages tissue and can lead to diabetes, heart disease, bronzing of the skin, and a variety of other problems when present in large amounts in the body.

How Long to Recover from Iron Deficiency

There’s no magic number here, but the honest answer is that this isn’t an overnight fix. Don’t expect to start a supplement or get an IV and feel amazing right away.

If you start taking an iron supplement regularly, you may notice a little less fog and heaviness in your legs within 2-4 weeks. That’s a good sign! But it just means the iron in your blood is improving. Your iron stores take a lot longer to refill, usually 3-6 months of taking iron consistently.

One study showed that even 11 weeks of supplementation wasn’t enough to maintain iron levels for a full season. So think of this as something you’ll manage over time, not a one-time fix you check off a list.

If your levels are low enough that your doctor recommends an IV, you may see results a bit faster, since it goes straight into your bloodstream rather than through your gut. But here’s the surprising part: studies haven’t shown that IV iron works better than supplements in the long run, just faster.

Some runners get one round of IV iron and are good for a long time. Others, like Coach Amanda, have needed to go back for more because their levels keep dropping again.

One more thing that’s easy to miss is that if you’re not eating enough for how much you’re training, your iron may never get back into a normal range, no matter how much you take. Not eating enough triggers your body to release a hormone that actually blocks iron absorption.

So even if you’re routinely taking your supplement, your levels may barely budge if you’re also underfueling.

We did a deep dive on an episode of the Tread Lightly Running Science Podcast. Listen to the full episode to learn more about the symptoms, when to see a doctor for bloodwork, and more about recovering from having low iron levels.

All right, now we have broken down the why, what, and how of runner’s anemia. As always, I hope this gave you a good place to start figuring out what’s going on with your body.

Looking for more runner nutrition?

• Sweat, Sodium and Runners: What The Research Really Says
• Tired After a Workout? What’s Normal and What’s Not
• Feeling Dizzy After a Workout? 9 Common Causes and Prevention