🩸 Hemoglobin—The Iron Marker That Shows Up Too Late

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When I first started looking into iron deficiency, hemoglobin was the only marker I really knew.

It came up in every routine blood test. It’s what doctors mentioned when I said I was tired. It was what my high school biology class taught me to care about.

So when my hemoglobin came back “normal,” I figured I was fine.

But I wasn’t fine. And I know I’m not the only one.

My symptoms said something was off—low energy, low motivation, that ever-present brain fog—but the labs didn’t back me up.

It wasn’t until I dug deeper, learning about ferritin, transferrin saturation, and other indicators, that I finally started to piece it together.

By the time hemoglobin drops, the damage has often already been done.

If you’ve ever been told “everything looks normal” but still don’t feel like yourself, this issue is for you.

Let's talk about what hemoglobin can (and can’t) really tell you.

Function: Is Iron Reaching Your Red Blood Cells?

🩸 Hemoglobin: Your Monthly Paycheck

Hemoglobin is the iron-rich protein inside red blood cells that carries oxygen from your lungs to the rest of your body. When it drops, your body isn’t delivering enough oxygen to keep up with demand.

But hemoglobin often stays in the “normal” range even when your iron is low.

It’s a lagging indicator. Your body fights to maintain hemoglobin as long as possible, even as other systems start to struggle.

Think of it like a paycheck. You might still be covering your bills, but if your savings (ferritin) are drained and your credit (transferrin saturation) is maxed out, it’s only a matter of time before something gives.

Hemoglobin is what many routine blood tests focus on because it’s used to diagnose anemia. But by the time your levels drop below ~12 g/dL (the common cutoff for women), your iron stores have already been depleted and your transport system has likely been faltering for a while.

Many routine blood tests check only hemoglobin because it’s the primary marker for diagnosing anemia. But you can be iron-deficient for months or even years before it falls.

If hemoglobin is all your doctor tests, you might not catch iron deficiency early enough.

By the time your hemoglobin drops below the lab reference range (usually ~12 g/dL for women), your iron stores have already been depleted and your transport system has likely been struggling for a while.

Here’s what happens:

1. Ferritin drops first → your iron savings start to run out

2. Transferrin saturation declines → your delivery system begins to struggle

3. Hemoglobin falls last → your energy, oxygenation, and focus crash

✅ Typical reference range for hemoglobin: 12–15.5 g/dL
⚠️ Deficiency: Below 12 g/dL
🚨 Severe deficiency (anemia): Below 10 g/dL

In other words:
❗ Low hemoglobin = Late-stage iron deficiency

Waiting for it to fall means missing early signs your body may already be struggling.

That’s why so many women are dismissed or misdiagnosed. They’re tired, foggy, and drained, but their hemoglobin looks “fine,” and testing often stops there.

💬 What’s your experience been like with iron testing? Have you ever had symptoms dismissed because your hemoglobin looked “normal”?