Feeling tired but your blood tests come back OK? Here's why.

It's a frustrating experience I hear from so many people: you're exhausted, foggy, maybe losing hair, feeling flat or anxious – yet when you finally get your blood work checked, you're told everything is "normal."

Yet you don't feel like yourself.

This is especially common when it comes to iron. Iron deficiency isn't a simple black-and-white state.

Iron status is a spectrum that moves from depletion, to deficiency, to anaemia at the other.

Iron deficiency anaemia is the most significant stage, and it's sometimes only here that your blood test results will fall completely outside the "normal" range.

When you're in the earlier stages – depletion or deficiency – results are often skewed toward the lower end of normal, but not always technically outside it.

And that can leave you feeling confused, or even dismissed, if you know things aren't quite right but your tests look "fine" on paper.

Watch: Six ways to support your body and brain as you age. Post continues below.

When "normal" isn't optimal.

Normal ranges are, of course, necessary.

Without them, there would be no consistent framework to flag when our health markers are clearly outside expected limits. But here's the catch: "normal" doesn't always mean optimal.

Nor does it necessarily mean that it's fine for you.

In iron tests, the marker of your stored iron levels is called 'ferritin'.

In Australia, the "normal" range for adult women spans from 20 to 200 µg/L — yet there's a world of difference between those two numbers, both in what they mean biochemically and in how a person actually feels. 

In my clinical experience, most menstruating women don't feel their best when their ferritin is below 50 µg/L.

Many feel better when it's closer to 80 or even 100 µg/L. So if your result comes back at 22 µg/L, your doctor may tell you that your iron is normal.

Technically, it is. But your body may already be whispering otherwise through persistent fatigue, foggy thinking, restless sleep, palpitations, cold hands and feet or mood changes.

That's why symptoms matter just as much as, if not more than, the numbers.

The complexity of interpreting results.

It can also get confusing when certain markers appear "high" on your test.

Take transferrin, for example, which binds and transports iron throughout your body.

If your transferrin or total iron-binding capacity (TIBC) is elevated, you might think you have too much iron. Yet elevated transferrin is actually your body's way of saying it wants more iron – there's not enough around to bind to.

Think of transferrin as a taxi for iron – your body makes more taxis (transferrin) in an attempt to pick up more passengers, the passengers being iron.

The normal range for transferrin for adult women is 2 – 3.6 g/L yet once this number goes above 2.6 g/L, it is typically a sign of iron hunger. 

Ferritin, too, can be misleading.

While it's the best iron storage marker we have, levels can appear falsely elevated if there's inflammation or infection.

For example, your true ferritin might be 20 µg/L – far too low to support feeling great – yet your test may report it as 80 µg/L because of inflammation.

On paper, it looks fine. In reality, you may still be iron deficient.

This is why it's so important to have your results interpreted in context.

An experienced health professional will consider not just the numbers, but also your symptoms and history, along with conducting a general blood test for inflammation such as CRP.

If you don't feel like yourself yet, and your blood tests come back "normal", it is still worth a closer look.

Image: Getty.

Catching the slide before anaemia.

When treatment is only offered after results fall outside the "normal" range, so many people miss the chance to correct their descending iron levels earlier.

Instead, they gradually slide from depletion, to deficiency, to full iron deficiency anaemia, leaving them feeling progressively worse along the way.

It would be far better for our health (and happiness) if we addressed low iron sooner, and ideally prevented it.

Regular testing helps, not just to flag a deficiency once it's advanced, but to track trends over time.

If you see your iron parameters falling every six months, or you find they are low, and they stay low despite dietary and/or supplemental efforts, that's an opportunity to intervene before symptoms deepen.

Your body is wise.

It speaks through symptoms, long before the numbers on a page tell the whole story. If you're tired but your tests come back "ok," it's worth asking: are my results truly optimal for me? And is there more context – from inflammation, infection, or nutrient interactions – that needs to be considered?

You deserve to feel energised, calm, clear-headed and resilient – not just scraping by.

Please don't dismiss the whispers of your body, even if your results look fine.

When iron is restored to healthy, robust levels, so many other aspects of health – from mood and sleep to metabolism and a host of hormones – often fall beautifully back into place.

Featured image: Getty.

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Dr Libby (PhD) is a nutritional biochemist, best-selling author and founder of BioBlends. Her new book Fix Iron First is out now.