Low Iron? This Is The Supplement That Actually Works For Active Women
Iron deficiency is one of the most common nutritional shortfalls in the world, and active women are disproportionately affected. Between 15% and 35% of female athletes are estimated to be iron deficient, yet many may not know how low their levels actually are. And while more and more women are making the connection between their low iron, fatigue, and performance, conventional advice to "eat more red meat" to get iron levels up often doesn't move the needle.
A new systematic review and meta-analysis1 published in Sports Medicine examined 42 randomized controlled trials to find out which dietary and supplementation strategies actually improve iron status in active women. Here's what you need to know.
Why are active women more prone to low iron?
There are two key reasons why women who are active (think those who exercise regularly and especially those training for endurance like runners, triathletes, or cyclists).
- Many women lose iron through menstruation each month, which already puts them at a baseline disadvantage compared to men.
- Exercise compounds the problem. Intense physical activity triggers the release of hepcidin, a hormone produced by the liver that acts as a gatekeeper for iron absorption. When hepcidin levels rise, the gut's ability to absorb iron from food and supplements drops significantly.
This means the women who need iron the most are often the least equipped to absorb it.
Low iron shows up as low ferritin first
One supplement form outperformed everything else
Researchers wanted to figure out what methods actually work to improve iron status in women who exercise regularly. To find out, they conducted a systematic review and meta-analysis of 42 randomized controlled trials focused specifically on active females, a population that's been historically underrepresented in nutrition research despite facing a uniquely elevated risk.
Ferrous sulfate, a bioavailable form of iron, emerged as the clear winner.
- Across the trials included in the review, ferrous sulfate supplementation significantly increased ferritin levels by an average of 12.61 ng/mL and raised hemoglobin, the protein in red blood cells that carries oxygen, by an average of 0.42 g/dL.
- Dietary interventions alone, including iron-rich eating patterns and food-based strategies, did not produce statistically significant improvements in iron status.
Ferrous sulfate, the most widely studied and commonly available form of supplemental iron, was the main strategy with consistent, meaningful evidence behind it.
Other supplemental iron forms (including chelated forms like iron bisglycinate) also improved iron markers in several trials. They are not yet as extensively studied as ferrous sulfate. Chelated iron tends to be more gentle on the stomach, and can be a great choice for those who may feel queasy while taking ferrous sulfate.
How to actually move the needle on your iron levels
Based on the study's findings, here's what the evidence supports for active women:
- Consider adding in an iron supplement: The review found that dietary strategies alone didn't significantly improve iron status in active women, and supplements are helpful. The dose that's best for you will be based on your training load and starting ferritin levels. That's why it's important to get your ferritin levels tested. Doses for iron supplements may range from about 8 milligrams a day to upwards of 60 milligrams. Based on your ferritin levels, and healthcare provider can provide more individualized recommendations.
- Time it strategically: Separate your iron from intense workouts. Ideally, you would take it in the morning before exercise or on a rest day. Avoid taking it alongside coffee, tea, dairy, or calcium supplements.
- Pair it with vitamin C: Ascorbic acid enhances iron absorption. A glass of orange juice or a vitamin C supplement taken alongside iron can meaningfully improve how much you absorb.
The takeaway
If you're an active woman who's been eating well and still feeling flat, your iron levels, specifically your ferritin, may be the missing piece. The research is clear that diet alone often isn't enough to move the needle, and that the form and timing of supplementation matter more than most people realize. Getting your ferritin tested is a simple first step that could change how you train, recover, and feel.