Ferritin “normal” but still exhausted? How to read your iron results
Told your iron is normal but still tired? Learn what ferritin, transferrin saturation and TIBC show, why gut health matters, and when to look further.
- Updated
- 6 min read
- By Charmaine Shepherd, IFM Certified Practitioner
Adapted from Charmaine’s free guide. Rewritten for the website mockup; the edits are awaiting her final approval.
Ferritin shows how much iron you have in storage. Many UK labs report results from around 13 to 15 µg/L as “normal”, but iron deficiency is usually confirmed below 30 µg/L, and many people still feel tired, foggy and cold well above that. In my clinic I look at the full iron panel alongside inflammation and gut health, because a low or stubborn ferritin often reflects absorption, blood loss or inflammation rather than diet alone.
“Your bloods are fine.” If you have heard this while still feeling exhausted, foggy, cold and nowhere near your best, this article is for you.
Iron is one of the most nuanced areas of testing. A single number, judged against a population reference range, can miss what is actually going on.
What does ferritin actually measure?
Ferritin is the protein your body uses to store iron. Think of it as the fuel tank, while serum iron is the fuel line. Serum iron goes up and down through the day; ferritin tells us how full your reserves are.
Iron is needed for haemoglobin, which carries oxygen to every cell. It is also needed for energy production, thyroid hormone conversion and making the brain chemicals dopamine and serotonin.
What is a normal ferritin level, and what is optimal?
Lab ranges vary, and many start at around 13 to 15 µg/L for women. NHS haematology guidance treats ferritin below 30 µg/L as indicating iron deficiency, and below about 12 to 15 µg/L as absent stores.
In practice, I see many women whose ferritin sits between 30 and 50 µg/L. Their result is reported as normal, yet they have the classic symptoms of low iron. In my clinic, I generally aim for ferritin of around 50 to 80 µg/L, adjusted for the individual.
Ferritin below about 50 µg/L is often seen alongside:
- tiredness that sleep doesn’t fix
- brain fog and poor concentration
- low mood and poor stress resilience
- hair thinning and shedding
- restless legs, especially at night
- feeling cold, and reduced exercise tolerance
Which iron tests should you ask for?
A standard check may give you only one or two numbers. A full iron panel gives a much clearer picture.
| Test | What it tells us | What to look for |
|---|---|---|
| Ferritin | Your iron stores | Below 30 µg/L indicates deficiency; I usually aim for 50 to 80 µg/L |
| Serum iron | Iron circulating right now | Varies with meals, time of day and infection, so never read on its own |
| Transferrin and TIBC | Your capacity to carry iron | High TIBC with low ferritin is a classic pattern of iron deficiency |
| Transferrin saturation | How much carrying capacity is in use | Below about 20% suggests deficiency; above 45% in women (50% in men) needs checking for iron overload |
| Haemoglobin, MCV, MCH | Whether anaemia has developed | These can be normal while ferritin is already low |
| CRP | Inflammation | Ferritin rises with inflammation, so it can look adequate when usable iron is low |
The grey zone is where most people are dismissed: haemoglobin is normal, so there is no anaemia, but ferritin is low and symptoms are real.
Why can ferritin look normal when iron is low?
Ferritin is an acute phase protein. It rises with infection and inflammation, including the low-grade inflammation of autoimmune conditions or an unsettled gut. A ferritin of 60 µg/L alongside a raised CRP and a low transferrin saturation may hide genuinely low usable iron.
That is why I never read ferritin in isolation.
Why won’t my ferritin go up?
You can eat plenty of iron-rich food and still be low, or take supplements for months and barely move your ferritin. When that happens, something else is usually driving the problem. I look at three areas.
Blood loss. Heavy periods are the most common cause of low iron in women before menopause. They deserve proper attention, not just more tablets.
Absorption. Iron is absorbed in the upper small intestine. That depends on enough stomach acid, a healthy gut lining and a well-balanced microbiome. Coeliac disease is an important cause, and NHS guidance recommends testing for it in iron deficiency anaemia.
Inflammation. Inflammation raises hepcidin, the hormone that closes the gates on iron absorption. I explain this in When iron won’t budge: the ferritin, hepcidin and microbiome connection.
How does gut health affect iron absorption?
The gut microbiome is not a bystander. Some bacteria compete for iron, particularly in an imbalanced gut. Beneficial bacteria ferment fibre into short-chain fatty acids such as butyrate, which help maintain the gut lining that absorbs iron.
Common clues that the gut is involved include bloating, irregular bowels, food reactions, past antibiotic courses, or iron tablets that cause stomach upset.
Can probiotics help iron absorption?
The best-studied strain is Lactobacillus plantarum 299v (now called Lactiplantibacillus plantarum). A 2019 meta-analysis found it improves the absorption of iron from food. Evidence that it raises ferritin over time is more limited, so I see it as a support alongside other measures, not a fix on its own.
The strain matters. A generic probiotic is not the same as one chosen for a specific purpose.
What does a functional approach to low iron look like?
- Full panel testing: ferritin, serum iron, TIBC, transferrin saturation, full blood count and CRP.
- Finding the cause: periods, gut function, coeliac screening, stomach acid and inflammation.
- A suitable form of iron, if needed: for example ferrous bisglycinate, which many people find gentler on the gut.
- Better absorption: pairing iron with vitamin C and keeping tea, coffee and calcium away from iron-rich meals.
- Targeted gut support: chosen for your picture, not a one-size formula.
- Retesting after around three months.
Please don’t take iron without testing first. Too much iron is harmful, and some people store too much, as in haemochromatosis.
When should you see your GP?
See your GP promptly if you have new iron deficiency and you are a man, have been through menopause, have lost weight without trying, have changes in your bowel habit or any bleeding. These need investigating through the NHS, and I always work alongside that.
Common questions
What ferritin level is too low?
Below 30 µg/L usually confirms iron deficiency. Many people have symptoms between 30 and 50 µg/L, even though this is often reported as normal. In my clinic I generally aim for around 50 to 80 µg/L.
Can you have low ferritin without anaemia?
Yes. Iron stores fall first, and haemoglobin drops later. You can have low ferritin with a normal full blood count, which is why some people are told everything is fine.
Why is my ferritin high when I feel tired?
Ferritin rises with inflammation, infection, liver stress and iron overload. A high ferritin needs interpreting with CRP and transferrin saturation, and sometimes testing for haemochromatosis.
How long does it take to raise ferritin?
Usually around three months of consistent treatment before ferritin changes clearly, which is why I retest at about that point. If it hasn’t moved, we look harder at absorption, blood loss and inflammation.
Should I take iron and probiotics together?
Many practitioners suggest spacing them, for example iron in the morning and probiotics later in the day. This is a sensible precaution rather than a strict rule, so ask about your own supplements.
Sources
- NHS: Iron deficiency anaemia
- Newcastle upon Tyne Hospitals: Adult haematology guidelines for GPs (ferritin thresholds)
- Royal United Hospitals Bath: Ferritin, a guide for GPs
- Health Education England: Hereditary haemochromatosis
- Vonderheid et al. (2019): Lactobacillus plantarum 299v and iron absorption, systematic review and meta-analysis
- Axling et al. (2020): L. plantarum 299v and iron status in female athletes
Normal vs optimal: 5 blood test ranges explained
Why am I always tired? 10 causes a standard blood test can miss
What happens at your first functional medicine appointment?
This article is for general information and isn't a substitute for personal medical advice. Please don't start or stop any medication without speaking to your GP or prescriber.