Ferritin in Athletes & Women
In my practice, I'm seeing more and more young women diagnosed with low ferritin — sometimes as low as 3 or 5 ng/mL. Optimal ferritin for most women sits between 50–70 ng/mL, and for active athletes, many sports medicine physicians recommend levels closer to 70–100 ng/mL to support energy production, oxygen delivery, and recovery.
The story is often the same: persistent fatigue despite adequate sleep, low energy after practice, and that heavy, dragging feeling after school or on weekends.
Many young women experience low ferritin in their late teens, particularly those who are highly active, have heavy menstrual cycles, or follow a diet low in heme iron sources. It is especially common in young athletes and is frequently found alongside undiagnosed celiac disease or Hashimoto's thyroiditis. Low ferritin doesn't mean you have either of these conditions — but if levels don't respond adequately to supplementation, testing for both is a reasonable next step.
The good news: ferritin levels can be restored relatively quickly. Most athletes notice meaningful improvements in energy and stamina within one to two weeks of starting treatment, with ferritin levels rising into a healthier range over 8–12 weeks of consistent supplementation.
Getting It Right: How to Supplement Effectively
Low ferritin is highly treatable, but there are a few key strategies that make a significant difference in how quickly and comfortably you recover.
1. Choose a High-Quality Iron Supplement
Not all iron supplements are created equal. Ferrous bisglycinate (chelated iron) is generally better tolerated than ferrous sulfate, with less GI irritation and comparable absorption. Well-regarded options include:
MegaFood Blood Builder — a whole-food-based iron supplement with added vitamin C and folic acid
Thorne Iron Bisglycinate — highly bioavailable chelated iron, gentle on the stomach
Pure Encapsulations Iron-C — ferrous bisglycinate paired with vitamin C for enhanced absorption
Avoid iron supplements made with ferrous sulfate if you have a sensitive stomach, as this form is the most likely to cause nausea and constipation.
2. Time It Right and Pair It Strategically
Take iron on an empty stomach in the morning. Gastric acid secretion is higher in a fasted state, which enhances iron solubility and absorption. Additionally, new research supports taking iron on alternating days rather than every day — a counterintuitive but well-supported finding. When iron is taken daily, the body's hepcidin levels (a hormone that regulates iron absorption) rise sharply within hours and remain elevated the following morning, effectively blocking the next day's dose. Alternate-day dosing keeps hepcidin lower and results in meaningfully better absorption overall.
Always pair iron with vitamin C. Vitamin C (ascorbic acid) converts ferric iron to the more absorbable ferrous form and can increase non-heme iron absorption by up to 3-fold. A glass of orange juice, a kiwi, or a vitamin C supplement taken alongside your iron supplement makes a real difference.
Avoid these foods within 2–3 hours of taking your iron supplement, as they bind to iron and significantly reduce absorption:
Calcium-containing foods — milk, yogurt, cheese, fortified non-dairy milks
Eggs — phosvitin, a protein in egg yolk, is one of the strongest inhibitors of non-heme iron absorption
High-phytate foods — bran cereals, oatmeal, whole wheat bread, legumes (beans, lentils)
Nuts and seeds
Tea and coffee — the polyphenols (tannins) in both beverages are potent iron absorption inhibitors; even decaf counts. Wait at least one hour after your supplement before having either.
Preventing Constipation
Iron supplementation — even with a gentler chelated form — can cause constipation, and it's one of the most common reasons people stop taking their supplements before ferritin levels are fully restored. Here's how to stay ahead of it:
Eat fiber-rich foods throughout the day. Aim for 25–28g of dietary fiber daily through vegetables, fruit, legumes, and whole grains — spread across meals, not all at once.
Add a fiber supplement, such as psyllium husk capsules, if needed. Important: take psyllium several hours away from your iron supplement (e.g., at night if you take iron in the morning), as psyllium will bind to the iron and reduce absorption.
Drink plenty of water — at least 8–10 cups daily. Fiber needs fluid to do its job.
Keep a gentle osmotic laxative on hand, such as Miralax (polyethylene glycol), just in case. It works by drawing water into the colon and is considered safe for short-term use.
A word on constipation: if it becomes chronic — beyond what iron supplementation explains — that's your gut communicating that something needs attention. Chronic constipation, like chronic diarrhea, is a signal worth investigating, not just managing. Working with a registered dietitian can help you build a meal plan that addresses both ferritin restoration and gut health at the same time.
Sample Daily Plan
Here's a practical framework for combining iron supplementation with fiber, hydration, and athletic fuel:
7:00 AM — Take your iron supplement Eat a piece of sourdough toast or ½ plain bagel with a light smear of peanut butter. Add an orange and a cup of chopped strawberries (both high in vitamin C). Take your iron supplement now. Sip water as you get ready — skip the coffee or tea until mid-morning.
9:00–10:00 AM — Coffee/tea window + optional second breakfast If you need caffeine, now is the time — at least 1–2 hours after your iron supplement. If you need a more substantial breakfast, choose a higher-fiber, solid protein option:
Greek yogurt with whole grain granola and berries
Smoothie with yogurt, flaxseed, and mixed berries
Oatmeal (rolled or steel cut) with chia seeds and fruit
Hard-boiled egg on an Ezekiel English muffin with peanut butter, honey, and a kiwi
12:30 PM — Lunch: protein + fiber The goal here is staying fueled and satisfied. Good options:
Big salad with grilled chicken or salmon, chickpeas, roasted vegetables, and a tahini or olive oil dressing over greens and farro
Turkey or tuna wrap on a whole wheat tortilla with avocado, spinach, tomato, and a side of fruit
Curry bowl with rice noodles, vegetables, and tofu or chicken added
Grain bowl with brown rice or quinoa, edamame, roasted veggies, and seeds/nuts
4:00 PM — Pre-practice snack (keep it light and easy to digest) If you are an athlete or plan your workout after work, before practice/workout, you will want quick-burning carbs and a little protein — not a lot of fat or fiber right now:
Banana with a small smear of almond butter
Rice cake with honey or a slight smear of peanut butter
A small bowl of white rice with soy sauce/tamari and a few edamame
Applesauce pouch + a small handful of pretzels
7:00 PM — Dinner: recovery and replenishment After practice, prioritize protein for muscle repair, complex carbs to restore glycogen, and fiber for gut health and overnight regularity:
Salmon with roasted sweet potato, steamed broccoli, and a lemon-olive oil drizzle
Chicken and vegetable stir-fry over brown rice with edamame and sesame seeds
Ground turkey taco bowls with black beans, rice, salsa, avocado, and cabbage slaw
Sheet pan chicken thighs with roasted root vegetables and quinoa
Before bed (if taking psyllium husk): Take psyllium husk capsules with a full glass of water, at least 6–8 hours after your morning iron supplement.
References
Sim M, et al. Iron considerations for the athlete: a narrative review. European Journal of Applied Physiology. 2019;119(7):1463–1478.
Stoffel NU, et al. Oral supplementation of iron absorption in iron-depleted women: a randomized cross-over trial. The Lancet Haematology. 2017;4(11):e524–e533.
Moretti D, et al. Oral iron supplements increase hepcidin and decrease iron absorption from daily or twice-daily doses in iron-depleted young women. Blood. 2015;126(17):1981–1989.
Hallberg L, Hulthén L. Prediction of dietary iron absorption: an algorithm for calculating absorption and bioavailability of dietary iron. American Journal of Clinical Nutrition. 2000;71(5):1147–1160.
Lynch SR, Cook JD. Interaction of vitamin C and iron. Annals of the New York Academy of Sciences. 1980;355:32–44.
Hurrell R, Egli I. Iron bioavailability and dietary reference values. American Journal of Clinical Nutrition. 2010;91(5):1461S–1467S.
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