A ferritin blood test measures the protein that stores iron in your body, so it shows how much iron you have in reserve, not just how much is moving through your blood right now. In the UK, ferritin under 30 µg/L points to depleted iron stores. It's the single most useful marker for unexplained fatigue.
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What ferritin actually is (without the textbook)
A man brought me his blood results in March. Active, mid-forties, training four times a week. His energy had fallen off a cliff and he couldn't work out why. The sheet had one number ringed: ferritin, 22 µg/L.
His GP had said it was "on the low side" and to "maybe eat more red meat". He wanted to know what the number actually meant.
One thing first, before the number meant anything.
When did the tiredness start, and did anything change just before it?
He thought about it. He'd cut red meat right back about six months earlier. Trying to eat cleaner.
There it was.
Ferritin is the protein your body stores iron in. A ferritin blood test measures your iron reserve: the tank, not the fuel currently in the line. That matters, because the tank empties first. Your stores run down for weeks or months before the iron in your blood drops, which is why ferritin falls before you're frankly anaemic (NICE CKS, Anaemia: iron deficiency).
If your report says serum ferritin instead, that's the same test. Serum just means it was measured in the liquid part of your blood. Same number, same meaning.
So ferritin tells you how much iron you've got banked. It doesn't tell you why the balance is where it is. A low number means the stores are down. What's draining them is the next conversation.
Ferritin is one marker in a recovery panel. For where it sits alongside hs-CRP and the rest, our CRP blood test guide is the wider view on what the inflammation side is doing.
Why your GP ordered it, or why your panel includes it
You probably didn't go looking for ferritin. Something put it in front of you.
The commonest NHS triggers: a fatigue work-up, low mood, hair shedding, restless legs at night, or a routine screen where someone added iron studies. The commonest private-panel triggers: an energy and recovery check, an athlete panel, or a full men's health screen that happened to include it.
Either way you've ended up with a number and not much explanation. "On the low side." "Within range." Neither answers the question you actually have.
The question you actually have is: what does my number mean, and is it why I feel like this?
What counts as low, normal, and high: the UK numbers
This is the section the search engines quote and the one most other ferritin articles get wrong, usually by using American units or no UK context at all. So, plainly. Here are the ferritin levels that matter and what each band means.
Under 30 µg/L: depleted iron stores
UK practice flags ferritin under 30 µg/L as iron deficiency in adults. That cut-off is well validated: at under 30 µg/L the test correctly identifies depleted iron stores in the large majority of cases (NICE CKS, Anaemia: iron deficiency).
The lower you go, the clearer it gets. A ferritin in single figures is unambiguous. The point to hold on to: low ferritin in a man is not a "take a supplement" finding. It's a "find out why" finding. More on that below.
30 to 100 µg/L: normal for the lab, not always optimal for you
Here's the bit nobody explains.
A man can sit at 35 µg/L, see "normal" printed on his report, and still feel flat. The reference range was built to flag iron-deficiency anaemia, not to tell you where your energy and recovery sit best. Normal for the lab's cut-off and optimal for how you feel are two different questions.
This is the same trap the testosterone range sets, and it's worth understanding properly: the myth of the normal range is the full version of that argument.
The honest position: a low-normal ferritin in a tired, training man is worth watching, not ignoring. The test tells you where you sit. What you do with that is a conversation, not a verdict.
Above the range: when high ferritin isn't more iron
This is where ferritin gets misread in the other direction.
Ferritin is an acute-phase reactant. That means it rises with inflammation, infection, recent heavy alcohol and liver strain, all independent of how much iron you actually have (NICE CKS, Anaemia: iron deficiency). So a high ferritin is not automatically a sign of too much iron.
A reading taken a week after a cold, or the morning after a big night, can print high and mean very little. That's not your baseline.
Genuine iron overload does exist. It's called haemochromatosis, it's often inherited, and it's a GP conversation, especially if it runs in your family. But a single high number, on its own, is a signal to look closer, not a diagnosis.
What low ferritin feels like in active men
If your stores are running down, the feeling usually arrives before the number gets dramatic. It tends to look like this.
Flat energy that a full night's sleep doesn't fix. Legs that go heavy in the back third of a session you used to finish easily. Breathlessness on efforts that never used to touch you.
Then the quieter ones. Recovery that's slipped. Hair shedding more than the seasonal norm. Restless legs at night. Hands that are cold when they didn't used to be.
Iron sits underneath all of that because it carries oxygen in your blood and feeds the energy production in your muscles. When stores run low, the system runs lean. The NHS lists tiredness, breathlessness and palpitations among the core signs of low iron (NHS, Iron deficiency anaemia).
Here's the honest qualifier, and it's the thing the cheap listicles leave out. Every one of those symptoms has other causes. Sleep. Training load. Thyroid. Low vitamin D. Stress. None of them, alone, means your iron is low.
That's exactly why you test. Not to confirm a fear. To find out which lever is actually the one to pull.
What a single ferritin reading does NOT tell you
A single number is a snapshot, and snapshots can mislead.
It doesn't, on its own, tell you the cause. A low ferritin means the stores are down; it doesn't say whether that's diet, absorption, or slow blood loss. Those are different problems with different answers, and the difference matters more in men than almost anywhere else in routine bloods.
It doesn't diagnose anaemia. That's a different measurement, the one a full blood count is built for. In fact your ferritin can be low while your full blood count still reads normal, because the stores empty before the blood count falls. That's iron deficiency without anaemia, and it's the commonest version of low iron that gets missed.
And a high reading doesn't mean more iron is better. As above, inflammation pushes ferritin up. The number has to be read in context, not in isolation.
The pattern matters more than the snapshot. One reading is a moment. A reading you've watched move tells you something a single value never can.
What changes when you actually have the number
The point of testing isn't the number. It's the loop.
Baseline. Address the cause. Wait. Retest. See what's changed.
Iron stores move slowly, slower than something like CRP, so the retest window is longer: think a few months, not a few weeks, to see a real shift in the blood. That's not a reason to skip the baseline. It's the reason to have one.
Without a baseline you're guessing. You change your diet, you feel maybe-slightly-better, and you never actually know. With a baseline you change one thing, give it time, and the retest tells you whether it moved. You find out how your levels have actually changed, instead of guessing from how you feel.
And the record is yours. If you ever take this to a GP, for a referral or a second opinion, you arrive with a timeline, not a single snapshot. That's something an eight-minute appointment isn't built to assemble for you.
How Andro Prime measures ferritin: Kit 2
The Energy & Recovery Check (Kit 2) measures ferritin alongside hs-CRP, Vitamin D and Active B12. The four markers most worth running together for active men who've lost a step and want to know why.
Finger-prick at home. UKAS ISO 15189-accredited lab (Vitall). 2 to 5 working days for results once the sample lands.
Your results come back through our dashboard, in plain English, reviewed by our GMC-registered medical lead Dr Ewa Lindo. And here's the part we're straight about: the test tells you where your ferritin sits. If it comes back low, we don't sell you an iron supplement. We hand you the number, the context, and a letter you can take to your GP, because that's where a low iron result belongs. See the blood test for tiredness and recovery.
Your next move
If you only read this section: ferritin measures your iron stores, the reserve that runs down before your blood count does. Under 30 µg/L points to depleted stores. A low result in a man is a GP conversation, not a supplement, because iron carries an overdose risk and depleted stores can signal slow blood loss. The retest, a few months on, is where the real answer is.
So here's the question.
You've got a number, or you're about to get one. Maybe from your GP, maybe from a panel, maybe because the tiredness finally got annoying enough to check. The number sits there. It doesn't explain itself.
What would you actually do differently if you knew where your iron stores sat, and which direction they were moving?
Find out where your ferritin actually sits. The Energy & Recovery Check measures ferritin alongside hs-CRP, Vitamin D and Active B12, the four markers worth running together for recovery-aware men. Finger-prick at home, UKAS-accredited lab, results in 2 to 5 working days. If your ferritin comes back low, we route you to your GP with context, not to a supplement.
System DB // References
- NHS. Iron deficiency anaemia. https://www.nhs.uk/conditions/iron-deficiency-anaemia/
- NICE CKS. Anaemia: iron deficiency. https://cks.nice.org.uk/topics/anaemia-iron-deficiency/
- British Society of Gastroenterology (2021). Snook, J. et al. Guidelines for the management of iron deficiency anaemia in adults. Gut 70: 2030–2051. https://www.bsg.org.uk/clinical-resource/guidelines-iron-deficiency-anaemia-in-adults
Frequently asked questions
What is a ferritin blood test?
A ferritin blood test measures ferritin, the protein your body stores iron in. It shows how much iron you have in reserve, not just how much is circulating right now. That's why it's the most useful single marker for iron status: your stores run down before the iron in your blood does, so ferritin drops before you're frankly anaemic. The same test is sometimes labelled serum ferritin on a report.
What is a normal ferritin level for a man in the UK?
UK labs vary, but a common adult-male reference range runs from about 30 µg/L up to roughly 300 µg/L. A result under 30 µg/L points to depleted iron stores. A value inside the range is reported as normal, but normal for the lab's cut-off is not the same as optimal for how you feel: a man at the bottom of the range can still feel the fatigue of low reserves. The number is read in context, not against the range alone.
What does low ferritin mean?
Low ferritin (under 30 µg/L in adult men) means your iron stores are depleted. It's one of the commonest measurable causes of unexplained fatigue, heavy legs late in a session, and slow recovery. But a low result is also the body asking a question: why are the stores down? In men, that question needs answering by a GP, because depleted iron can signal slow blood loss. It is not something to self-treat with an iron supplement.
What does high ferritin mean?
Ferritin rises with inflammation, infection, recent alcohol and liver strain, all independent of how much iron you actually have. So a high ferritin is not automatically iron overload, and a single high reading after a cold or a heavy week is not a baseline. Genuine iron overload (haemochromatosis) exists and is a GP conversation, especially with a family history. A high result on a repeat test, with no obvious cause, is one to take to your GP.
Can ferritin be low when my full blood count is normal?
Yes, and this is the bit most people miss. Iron stores empty before your haemoglobin drops, so ferritin can be low while a full blood count still reads normal. That's iron deficiency without anaemia. It's why a normal FBC doesn't rule out low iron, and why ferritin is worth measuring directly rather than inferring from a blood count.
Will a supplement fix low ferritin?
Low ferritin in a man is not a supplement decision. Iron has a real overdose risk, it needs to be dosed on your specific numbers, and a low result needs its cause investigated first, because in men depleted iron can point to slow blood loss. That's why Andro Prime doesn't sell iron supplements: a low ferritin result routes you to your GP with context, not to a product.