What Your Doctor is Really Thinking #6: The Missing Information in Your Ferritin Lab Results

You’re back to see me - not because anything’s new, but because you’ve been carrying around a blood test result that said “normal” for three weeks, and you still feel dreadful.

Exhausted.

Restless legs at night.

More hair in the shower drain than on your head.

A brain like giant marshmallows.

Janet from down the road already told you this was probably just the result of overdoing it at the gym to impress the new PT (honed, toned and very smiley), and staying up every later than ideal every night for the last month to watch Love Island… and it might well be - but you want to know what “normal” actually means, because it doesn’t match how you feel.

Let’s actually look at what’s been checked, because “normal” may be true, but normal what exactly?

Thyroid - checked, normal.

Full blood count (FBC) - checked, normal.

Both reasonable places to start. An FBC tells me about your haemoglobin - whether you’re anaemic or not - but that’s not the same question as whether your iron stores are running low. You can be a long way into iron deficiency before your haemoglobin so much as blinks.

Ferritin (fancy name for iron) - checked, normal.

So your labs were ‘normal’ - that’s a reassuring place to start in terms of dangerous pathology, but it’s just the headlines. I want to look at the actual numbers and dig a bit deeper into what life looks like for you at the moment.

• What was the ferritin - the actual number?

• What have your periods been doing - heavier, more erratic, closer together, further apart? Perimenopause is often a long, messy farewell tour for periods before they stop for good, and that farewell tour can mean more blood loss than the season finale of CSI Miami, and a quietly dropping ferritin in the process.

• Anything chronically grumbling in the background - a flare of something autoimmune, ongoing low-grade inflammation, a recent infection? These can matter more than many realise.

• What’s your diet like? A reduced appetite/intake - particularly common now with the advent of GLP-1s can mean you’re missing the mark when it comes to important micronutrients.

• Do you have any known issues that affect how you absorb nutrients - inflammatory bowel disease, coeliac, previous bowel/gastric surgery, bile acid malabsorption… the is list long!

Here’s the bit that makes this genuinely tricky rather than just under-recognised: ferritin isn’t just your iron gauge, it’s also what we call an ‘acute phase reactant’ - meaning it rises with inflammation, infection, or anything inflammatory smouldering in the background. A ferritin of 70 in an otherwise well person is a completely different story to a ferritin of 70 in someone slap-bang in the middle of a flare of Crohn’s Disease, or having just stumbled out of bed after a week with Covid.

The number can look reassuring while the actual iron warehouse behind it is close to empty.

In midlife, there’s also an overlap problem. Iron deficiency and perimenopause share an almost identically annoying symptom list - fatigue, brain fog, hair thinning, restless legs, flattened mojo - which makes it very easy for patient and doctor alike, to file everything under “hormones” and never go looking for iron at all.

Also - both things can be true at once. Being in the prime of your life (aka menopause) doesn’t give you a free pass for all other medical problems. In fact, many of them present during these exact years. Treating the oestrogen side without checking the rest - especially iron, means you might still feel dreadful and have no idea why the ‘fix’ only half-worked.

Yes - and this is where I want the real nitty-gritty, not the lab’s “normal” stamp, but the details behind the headline:

• Full iron studies and inflammatory markers (CRP/ESR), if the ferritin comes back normal, but your symptoms tell a different story, then I need to try and unpick the what your iron is actually doing? Is it plentiful and all going into red cell production? Or is most of it being side-lined as a consequence of an underlying inflammatory process?

• Thyroid Function - another big mimic of both perimenopause and iron deficiency. Not the focus of this post, but worthy of a mention. (Check out this clinic episode to understand more about thyroid function tests 🎧)

• Coeliac Screening - autoimmune gluten-triggered condition. More common if you have a first degree relative with it (up to 1 in 10), and often not at the front of our minds unless you specifically come complaining of belly trouble, but can cause iron deficiency.

The WHO’s own cut-off for iron deficiency is a ferritin under 15 µg/L. In everyday practice, most of us treat anything under 30 as diagnostic - a meaningfully more generous bar than the WHO’s, but even 30 is a long way from what I’d call optimal.

Sometimes a sub-optimal ferritin - that may still be correctly labelled as ‘Normal’ - needs treating. That decision comes down to an assessment of the labs in the context of your symptoms.:

✅ Skipping about the place like Kylie at Brighton Pride and a ferritin of 50 - fine.

❌ Feeling more like Meatloaf at the end of a particularly gruelling world tour with a ferritin of 50 - perhaps we need to top you up.

❌ Moves worthy of a headline spot in Riverdance at 1am when you’re trying to get to sleep, with a ferritin of 50 - again, a top up is probably a sound move.

If the ferritin comes back low, it needs acting on - and part of that will be supplementation. If it comes back sub-optimal (ie. below 70) and you have symptoms that are highly suggestive of iron deficiency, it may also be appropriate to treat with iron supplements. In either case, we need to check in after a couple of months to repeat the bloods and also to see if your symptoms have changed at all.

• Iron supplementation, taken with vitamin C to help absorption, away from caffeine, calcium, PPIs, and tannins, which all block it.

• Recheck in three months, tracking the actual ferritin number this time, as well as how you feel.

If a blood test comes back “normal”, but you don’t feel right, say so.

When it comes to iron, ask whether the result is optimal, not just technically within range. And if there’s anything chronically inflammatory going on for you, ask whether that could be quietly propping up the number.

You’re allowed to ask these questions - they’re not you being a difficult patient - you’re just well-informed and want to be involved in the discussion.

‘Normal’ is not always the same as optimal.

Keep up the work at the gym - the PT is quietly impressed. And Love Island isn’t worth losing sleep over.

Dr White

* The content of these emails/posts/publications/audio files is intended as general health and wellness information, not as individual medical advice. Please consult your own doctor for advice that is specific to you and your needs.