You’re juggling a demanding job, a bustling home life, and all those tiny details that keep everything on track.

You tell yourself the exhaustion is normal, just part of being busy. But no matter how much sleep you get or how much iron-rich food you eat, the fatigue lingers.

Iron deficiency is often seen as a simple fix: eat more iron, take a supplement, and your energy should bounce back. But for many women, it’s not that simple.

When Iron Supplements Stop Working

During my second postpartum, when the all-too-familiar fatigue of iron deficiency hit, I did what I always did. I went back to my iron supplements, expecting my energy to return.

I used to feel the difference pretty quickly after taking iron. But now? Nothing. The exhaustion lingered, and I couldn’t figure out why.

That’s when I started investigating. If I was taking iron, why wasn’t my body responding?

If your body isn’t absorbing iron properly, eating more of it won’t make a difference.

This issue dives into why iron deficiency isn’t just about diet and what to do when increasing iron intake isn’t working.

Iron Deficiency 101: It’s Not Just About Low Iron Intake

Iron plays a critical role in oxygen transport, energy production, and overall health. Our bodies carefully regulate iron balance, circulating some in the blood (in hemoglobin) and storing the rest in ferritin. When this system is disrupted, symptoms like fatigue, dizziness, headaches, and brain fog appear.

But not all iron deficiencies are the same.

There are two main types of iron deficiency:

🔴 Absolute Iron Deficiency → You have low iron in your blood and low iron stores. This often results from blood loss, inadequate dietary intake, or increased iron needs (like during pregnancy or intense exercise).

🟡 Functional Iron Deficiency → Your blood iron is low, but your iron stores are normal or even high. In this case, your body isn’t effectively using or absorbing the iron you consume, so taking more iron may not help.

👉 Why does this matter? Because the right solution depends on the type of deficiency you have.

If your body is actively blocking iron absorption, adding more iron to your diet won’t solve the problem.

You need to address what’s preventing absorption.

The Hidden Reasons Your Body Might Be Rejecting Iron

Many things—individually or all at once—can cause iron deficiency. In last week’s issue, I talked about how we can naturally boost our iron levels through our diet. So what if, after a few weeks, it doesn’t seem to make any difference?

Here are four key factors that could be preventing iron absorption:

🦠 Gut Health: The Iron-Gut Connection

Your gut plays a major role in iron absorption, and recent research shows that your gut bacteria can influence how much iron your body actually uses.

🔹 Poor gut health (from conditions like H. pylori infection, celiac disease, or inflammatory bowel disease) can damage the intestinal lining, reducing iron absorption.

🔹 Imbalanced gut bacteria may impact how iron is stored in the body. Mice studies have shown that without gut microbes, ferritin (iron storage) disappears.

🔥 The Hormonal Block: How Hepcidin Controls Iron Absorption

Iron absorption isn’t just about what you eat. It’s regulated by hepcidin, a hormone that determines how much iron your intestines absorb.

When hepcidin levels are too high, your body literally blocks iron absorption, no matter how much you consume.

🔹 Chronic inflammation (from conditions like autoimmune diseases, infections, or even stress) raises hepcidin levels, making iron supplements ineffective.

🔹 Hormonal changes (including pregnancy, menopause, and certain medications) can also disrupt iron regulation.

🧬 Genetic Causes: When Your Body Simply Won’t Absorb Iron

Certain genetic mutations can increase hepcidin or disrupt iron transport, making it harder for the body to absorb and use iron.

🔹 Iron-Refractory Iron Deficiency Anemia (IRIDA)⁵: A rare gene mutation causes excess hepcidin, blocking iron absorption and making oral supplements ineffective.

🔹 Transferrin Receptor 1 (TfR1) Mutations: TFRC gene mutations can impair iron uptake by cells, leading to a novel subtype of iron-deficiency anemia.

☣️ Environmental Factors: How Toxins Can Sabotage Your Iron Levels

Certain environmental toxins and pollutants can compete with iron for absorption or disrupt iron metabolism, making it harder for your body to maintain healthy levels.

🔹 Cadmium Exposure: Found in cigarette smoke, industrial pollution, and some contaminated foods (e.g., rice, shellfish, and organ meats). Cadmium competes with iron for absorption, worsening deficiency.

🔹 Lead Toxicity: Lead exposure (from old pipes, paint, and industrial pollution) can disrupt iron metabolism and contribute to anemia.

🔹 Microplastics & Endocrine Disruptors: Emerging research suggests that microplastics and chemicals like BPA (found in plastics and food packaging) may dysregulate nutrient absorption, including iron.

If you’ve been stuck in the “eat more iron” trap without results, here’s another approach:

1. Test, don’t guess. Instead of relying on hemoglobin levels alone, ask for tests that check ferritin, transferrin saturation, and hepcidin to get the full picture.

2. Prioritize gut health. If your gut isn’t absorbing nutrients properly, iron supplements won’t help. Consider probiotics, digestive enzymes, and gut-friendly foods.

3. Address the root cause. If inflammation, hormonal imbalances, or environmental toxins are at play, tackling those will make your iron intake more effective.

If increasing iron intake hasn’t helped your fatigue, it’s time to rethink the approach. The real issue may not be how much iron you’re getting, but whether your body is actually using it.

I learned this the hard way.

When my iron supplements stopped working, I took too long to dig around for answers.

What I didn’t expect was that the issue wasn’t just iron. It was my gut. Around the same time, I was diagnosed with new food sensitivities, especially to gluten and high-FODMAP foods.

Looking back, it makes sense. If your gut isn’t absorbing nutrients properly, iron won’t make it into your bloodstream. No matter how much I was taking, my body simply wasn’t getting what it needed.

Once I started paying attention to my gut health, things changed.

🔍 Feeling more energized starts with smarter iron strategies—not just more iron.

💬 Have you struggled with iron absorption? What has helped (or not helped) for you? Reply and let me know!

🩸 Iron supplements work best when you take them the right way. Next week, I’ll cover different supplementation options and how to choose the right one for you.

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1  Defined here as a serum ferritin level of less than 30 μg/L.

2  Defined as transferrin saturation less than 20% with serum ferritin level greater than or equal to 30 μg/L.

3  Defined here as a serum ferritin level of less than 30 μg/L.

4  Defined as a serum ferritin level of less than 15 μg/L, less than 12 μg/L, and less than 10 μg/L, depending on the study.

5  For those interested, IRIDA is a genetic disease caused by a mutation in TMPRSS6, the gene encoding transmembrane protease, serine 6 (i.e., matriptase-2).