This is one of the things I’ve been building towards. It’s a free tool that reads your iron bloodwork against the actual research on women’s physiology.

I built it because my own labs have come back “fine” more times than I can count. It’s like systemic gaslighting. And I know I’m not alone.

So here she is.

This week, I’m walking you through why there have long been fundamental problems with the long-used references ranges — and why I’m so glad this tool finally exists.

When your lab reports ferritin, the "normal" range comes from large reference-population studies. Theses studies took a sample of people, measured their ferritin, and used the spread of values to define "normal." The reasoning is that this is what’s normal in a population; this is what we expect to see.

A 2024 systematic review looked at where those reference ranges actually come from. Of the studies establishing the cutoffs labs use today, 49% didn't exclude participants who were themselves iron-deficient. 52% didn't follow guideline-recommended methodology (like CLSI standards) for how a reference interval should be set in the first place.

This means that the "normal" range has been built on people who are not normal (with respect to their iron status). You can already see how this is a major problem for diagnosis.

The result: the female ferritin lower limit of "normal" sits at a median of 8-11 μg/L across labs. Which is insanely low.

Research in young women shows your gut starts working harder to absorb iron at around 50 μg/L. That’s the threshold where your body recognizes a shortfall and starts compensating.

The actual physiologically-derived thresholds, where your bone marrow starts struggling to make hemoglobin properly, sit around 25 to 30 μg/L.

So if your ferritin comes back at 35 μg/L and your lab says "normal," your gut has already been working overtime to extract iron from food for some time.

If your ferritin comes back at 15 μg/L — already physiologically iron-deficient — your bloodwork would be classified as “normal” and you’d be sent on your way.

And this is exactly what I built the Iron Lab Explainer to clarify: how to understand your lab results based on what we now know from the research into the stages of iron deficiency.

We’re still waiting for references ranges to catch up with the science. But in the meantime, here’s how to know what your number actually means.

🩸 At your next blood draw, ask for the ferritin number, not just the final interpretation.

📏 Compare your ferritin to two physiologically important thresholds: Above 50 μg/L, your body has stopped compensating for iron shortage, which is great. Below 30 μg/L, you're iron deficient by current research standards, even if the lab calls it "normal."

🔬 Run your bloodwork through the Iron Lab Explainer to read your numbers against the most up-to-date research. It's the tool built for exactly this problem. Every threshold traces to an appraised study.