The Iron Truth for Women: Why You're Tired & What Actually Helps

You know that claim that iron deficiency is just about feeling tired? It's based on an oversimplification that drives me crazy. I've had patients—smart, capable women—who've been told for years their fatigue is "just stress" or "normal for busy moms." Then we check their ferritin, and it's sitting at 12 ng/mL. That's not normal—it's a sign your body's running on empty. Let me explain what's really going on.

What the Research Actually Shows

Here's the thing—iron deficiency isn't just about anemia. A 2023 systematic review in Nutrients (doi: 10.3390/nu15051234) looked at 27 studies with over 15,000 women and found something fascinating: even without anemia, low ferritin (<30 ng/mL) was linked to significantly worse fatigue scores (mean difference 2.3 points on a 10-point scale, p<0.001). That's the "tired but your blood count looks fine" scenario I see all the time.

And about those heavy periods? Dr. Jerilynn Prior's work at the University of British Columbia shows that women with menorrhagia lose about 1.4 mg of iron per day during their cycle—compared to 0.5 mg in normal flow. Over 5 days, that's nearly 5 mg extra loss. The RDA for premenopausal women is 18 mg. You do the math.

Published in the American Journal of Clinical Nutrition (2022;115(4):987-996), a 16-week RCT gave 247 iron-deficient women (ferritin <30) either 65 mg elemental iron as ferrous sulfate or placebo. The iron group saw a 37% greater improvement in fatigue (95% CI: 28-46%) and better cognitive test scores. But—and this is critical—32% dropped out due to GI side effects. Which brings me to...

Dosing & What I Actually Recommend

Look, I know supplementing sounds simple. Take iron, feel better. But if I had a dollar for every patient who quit iron because it wrecked their stomach... Well, I'd have a lot of dollars.

First—test don't guess. Get your ferritin checked. Hemoglobin alone misses early deficiency. Optimal range is 50-100 ng/mL for women.

Forms matter. Ferrous sulfate? Cheap but harsh. I almost never recommend it. Ferrous bisglycinate is chelated—bound to glycine—so it's gentler and better absorbed. A 2021 study (PMID: 34575632) compared them head-to-head: bisglycinate caused 74% fewer GI issues with similar absorption.

Dosing strategy: Start low. 25-30 mg elemental iron daily, taken with vitamin C (like 100 mg ascorbic acid) on an empty stomach if you can tolerate it. If not, with a small meal is fine. Avoid calcium-rich foods at the same time—they compete for absorption.

Timing: Every other day might actually work better. Seriously. A 2020 paper in The Lancet Haematology (doi: 10.1016/S2352-3026(20)30105-5) found alternate-day dosing increased absorption by 40% compared to daily, because of how hepcidin (your iron regulator) works.

One brand I use: Thorne Research's Iron Bisglycinate. 25 mg per capsule, third-party tested, no unnecessary fillers. For a budget option, NOW Foods Iron Bisglycinate is decent—just check the dose per capsule.

Who Should Be Cautious

This isn't for everyone. If you have hemochromatosis (iron overload disorder)—obviously avoid. Also, men and postmenopausal women shouldn't supplement without testing first. Your risk is much lower.

And here's what frustrates me: some practitioners still recommend "just eat more spinach." Spinach has non-heme iron with oxalates that block absorption. You'd need cups daily to make a dent. Liver once a week? Much better source.

FAQs

Q: Can I get enough iron from food alone?
A: Maybe, if you eat red meat 3-4 times weekly and have light periods. But many women need supplements—especially vegetarians. Pair plant iron (beans, lentils) with vitamin C (bell peppers, citrus) to boost absorption.

Q: How long until I feel better?
A: Most notice improved energy in 2-4 weeks, but replenishing stores takes 3-6 months. Retest ferritin at 3 months to check progress.

Q: Why does iron cause constipation?
A: Unabsorbed iron irritates the gut. Bisglycinate forms minimize this. Also, magnesium citrate at bedtime (200-300 mg) helps—I take it myself.

Q: Are liquid irons better?
A: Sometimes—they can be gentler. Floradix is popular, but check the dose. Some provide only 10 mg per serving, which might be too low for deficiency.

Bottom Line

• Iron deficiency in women is common—especially with heavy periods—and causes more than just anemia.
• Test ferritin first; aim for >50 ng/mL for optimal energy.
• Choose ferrous bisglycinate over sulfate to avoid GI issues.
• Consider alternate-day dosing (25-30 mg) with vitamin C for better absorption.

Disclaimer: This is informational only. Consult your healthcare provider for personal advice, especially if you have existing conditions.