Here’s a statistic that should make every runner pay attention…
Research shows that female rowers with ferritin levels below 20 ng/mL were 21 seconds slower over 2 kilometers than those with normal levels, despite having normal hemoglobin.
If you’re a runner who’s been told your iron levels are “normal” but still experience unexplained fatigue, poor recovery, or performance decrements that don’t match your training, this article is for you.
We’ll dig into the research and empirical evidence of…
- Why standard medical reference ranges fail athletes
- The optimal ferritin targets that separate mediocre from peak performance.
- Strategic testing protocols
- And evidence-based supplementation strategies
When “Normal” Fails Runners
Your doctor calls with your bloodwork results.
“Everything looks fine,” she says.
Your hemoglobin is normal, so there’s no anemia.
But you’re not fine, you’re exhausted, your workouts feel harder than they should, and your race times are stagnating.
Medical labs typically define normal ferritin as 12-300 ng/mL for women and 12-400 ng/mL for men.
These ranges were designed for the general population, not for athletes with high metabolic demands who break down and utilize iron at dramatically accelerated rates.
Research published in the International Journal of Sport Nutrition and Exercise Metabolism examined 165 female collegiate rowers.
A full 30% had low ferritin with normal hemoglobin.
The researchers found that performance decrements were statistically significant even when ferritin levels were raised to 25 ng/mL, well above the clinical deficiency threshold of 12 ng/mL.
Here’s the disconnect: your doctor is trained to prevent anemia, not optimize athletic performance.
A standard complete blood count only measures hemoglobin, it doesn’t assess your iron stores through ferritin.
You get told “everything looks fine” while leaving seconds on the table every single race.
The Performance Continuum: From Deficient to Optimal
Understanding iron status isn’t binary, it exists on a continuum with three distinct stages.
Stage 1 is iron deficiency anemia (IDA): low ferritin AND low hemoglobin, with obvious performance impairment and clear medical diagnosis.
Stage 2 is iron deficiency without anemia (IDNA): low ferritin but normal hemoglobin, the most controversial and misunderstood category where many runners unknowingly suffer.
Stage 3 is suboptimal iron stores: ferritin technically “normal” (12-30 ng/mL) but suboptimal for athletes, causing performance decrements without obvious clinical signs.
This third stage is where the real opportunity lies.
The mechanism extends far beyond oxygen transport.
While everyone knows hemoglobin carries oxygen to your muscles, iron plays equally critical roles in mitochondrial enzymes and oxidative metabolism.
Iron-dependent enzymes are essential for aerobic energy production.
A study in the International Journal of Sport Nutrition found that women with depleted iron stores exercised 14% less time to exhaustion than those with normal stores, even though their hemoglobin levels were identical.
Why does performance suffer with normal hemoglobin?
The answer lies in impaired lactate metabolism and premature reliance on anaerobic energy systems.
Without adequate iron stores, you’re forced to dig into your anaerobic systems earlier during sustained efforts, accumulating lactate and fatiguing more rapidly.
The Ferritin Sweet Spot
So what should you actually target?
The evidence points to ranges significantly higher than standard medical thresholds.
For female runners: minimum 30-40 ng/mL (accounting for the 27% day-to-day variability), with optimal levels at 40-50+ ng/mL.
For male runners: minimum 40-50 ng/mL, with optimal levels at 50-100+ ng/mL.
Recent research published in Scientific Reports [3] suggests that elite male rowers with ferritin above 75 ng/mL show different post-exercise iron metabolism patterns compared to those below this threshold.
Why do athletes need higher levels?
Training creates multiple iron drains:
- increased utilization for erythropoiesis (red blood cell production)
- exercise-induced losses through hemolysis and foot strike impact
- gastrointestinal bleeding
- sweat losses,
- and an inflammatory response to training that actively inhibits iron absorption.
Here’s something most runners don’t know: research in The Journal of Nutrition shows that ferritin can vary by 15% in men and 27% in women from day to day.
This variability matters.
If you’re targeting the bare minimum of 30 ng/mL, normal fluctuations could drop you into the deficiency range on any given day—especially during hard training blocks or illness.
The Hepcidin Factor
Understanding hepcidin is critical for optimizing your iron strategy.
Hepcidin is the master regulator of iron homeostasis, and it functions by blocking iron absorption in your gut and inhibiting iron recycling in your macrophages.
Here’s the problem for runners: endurance exercise increases interleukin-6 (IL-6), which triggers hepcidin production 3-6 hours post-workout.
Research demonstrates that a prolonged bout of running increases hepcidin by 51% and reduces fractional iron absorption by 36% compared to rest.
This effect lasts several hours after training.
Simply put: that iron-rich meal or supplement you take immediately after your long run?
Your body is actively blocking its absorption.
This is why female endurance athletes face compounding challenges, menstrual losses plus exercise-induced depletion plus inflammation-mediated absorption barriers create a perfect storm for deficiency.
Will eating more iron-rich foods solve the problem?
One of the major issues with getting enough iron is that it’s been shown to be notoriously difficult for the body to absorb and utilize.
In fact, iron bioavailability is estimated to be only 14% to 18% for those consuming animal products and as low as 5% to 12% for plant-based eaters.
This is the result of many factors, including…
- Iron-rich plant foods often contain phytates, compounds that bind to iron, rendering it inaccessible to the body as it travels through the digestive tract.
- Many common foods such as calcium, protein and caffeine have all been shown in research to inhibit the absorption of iron.
- There are also the polyphenols (which include tannins), as well as certain micronutrients and proteins in our foods that inhibit absorption.
This is why it’s usually recommended runners be on an iron supplement unless they’ve had their levels tested and they know they are above normal.
What to Look for in an Iron Supplement
Traditional iron supplements you’ll find in Walmart, Amazon and Walgreens use ferrous sulfate as the main ingredient.
Unfortunately, studies show that your body only absorbs 10-15% of iron from ferrous sulfate, with the remaining 85-90% staying in your digestive tract and causing nausea, constipation, and cramping.
And, once again, some ground-breaking research seems to have found a solution to this absorption problem.
Clinical studies demonstrate that iron bisglycinate—a chelated form of iron—produces 50% fewer gastrointestinal side effects compared to ferrous sulfate while maintaining superior absorption rates.
Iron bisglycinate works because the glycine molecules protect the iron through stomach acid, delivering it directly to your small intestine where absorption occurs.
Research shows that 60mg of iron bisglycinate provides equivalent therapeutic benefits to much higher doses of ferrous sulfate. This means you get better results with lower doses and fewer side effects.
Take with other vitamins/minerals know to aid absorption
Another “hack” to increasing iron absorption is to always take your iron with ingredients that have been shown to increase bioavailability.
These include the “normal” suggestions, such as vitamin c, b6 and b12.
But, you can also add ingredients like Alpha GPC, which has been shown to increase absorption 4 x more than taking iron alone; or BioPerine, which increases bioavailability by 40%.
That’s why I highly recommend checking out ​MAS Iron​
Their formula combines iron bisglycinate with buffered vitamin C, active folate, AlphaGPC and Bioperine B12 in precise ratios shown to maximize iron uptake.
To my knowledge, it’s the only iron supplement specifically formulated for endurance athletes that addresses both absorption optimization and red blood cell formation support.
Your Action Plan
Start by getting tested properly: request serum ferritin specifically, include a CBC for hemoglobin, and consider C-reactive protein (CRP) to rule out inflammation.
Don’t accept “normal” without seeing your actual numbers.
Compare your results to athlete-specific ranges, not general population standards.
If your ferritin is below 30 ng/mL, implement oral supplementation (25-100 mg elemental iron) combined with dietary optimization, strategic timing around training, and retesting in 6-8 weeks.
If your ferritin is 30-40 ng/mL, maintain aggressive dietary focus, consider low-dose supplementation, and monitor closely during high-volume training phases.
If your ferritin is above 40 ng/mL, maintain through diet, test periodically, and supplement only if levels decline.
