Ferritin blood test: what it measures and what can change it
Ferritin shows how much iron is stored in the body. Inflammation, infection and liver problems raise it whatever the iron stores are.
General information about the test, from Hea's guide and the NHS · Last reviewed 5 November 2026
What it measures, and why GPs check it
Ferritin
Ferritin shows how much iron is stored in the body. Inflammation, infection and liver problems raise it whatever the iron stores are.
It is the usual first test for iron deficiency, the most common cause of anaemia.
Haemoglobin
Haemoglobin is the protein in red cells that carries oxygen. It is the main number in a full blood count.
A low level is anaemia; the cause matters more than the number itself.
Levels in UK guidance
Ranges differ between labs — your report shows your lab's range.
Ferritin
- Below 30 µg/L iron stores are generally low and below 15 µg/L they are absent, by British guidance, which asks the GP to treat it and look for the cause. BSG guidelines for the management of iron deficiency anaemia in adults (2021; PMID 34497146), Definitions; BSH guideline for the laboratory diagnosis of iron deficiency (2022; PMID 34693519); ASH 2026 (PMID 42747316)
- A high ferritin is followed up with transferrin saturation and a look at alcohol, liver and inflammation, not treated on its own. EASL 2022; BSH 2018
Haemoglobin
- WHO and UK guidance use below 130 g/L for men and below 120 g/L for women as anaemia. WHO guideline on haemoglobin cutoffs to define anaemia (2024); BSG guidelines for the management of iron deficiency anaemia in adults (2021; PMID 34497146)
- Laboratories phone a doctor the same day below 70 g/L (below 50 g/L with small red cells) and above 190 g/L. RCPath G158 v2 (2026), Table B1
- Anaemia is worked up with the red cell size (MCV) and with ferritin, B12 and folate; the pattern points to the cause. Lab Tests Online UK: Full blood count (FBC); BSH guidelines for cobalamin and folate disorders (2014; PMID 24942828)
What can shift the number
Now or in the last 3 months
- Pregnant. In pregnancy the usual ranges for many tests are different: show these results to your midwife or GP. NICE NG201 Antenatal care (2021); NICE NG3 Diabetes in pregnancy (2015, updated 2020); RCOG Green-top Guideline 76: thyroid disorders in pregnancy (2025; PMID 40240075); NICE NG239 (2024) rec 1.3.2; BSG guidelines on the management of abnormal liver blood tests (2018); Lab Tests Online UK: Lipid profile; C-reactive protein (CRP); ESR
- An infection or illness in the 6 weeks before. An infection or inflammation can raise ferritin, CRP, ESR and platelets for some weeks, and can raise or lower white cells. Ferritin can then stay within the laboratory's range even when iron is low. Lab Tests Online UK: Ferritin; C-reactive protein (CRP); ESR; Full blood count (FBC); Platelet count; BSH guideline for the laboratory diagnosis of iron deficiency in adults and children (2022; PMID 34693519)
- Gave blood, lost blood or had a transfusion. Bleeding, giving blood or a transfusion changes blood count and iron results: each blood donation removes iron, and platelets rise after bleeding. BSG guidelines for the management of iron deficiency anaemia in adults (2021; PMID 34497146), History and examination; NHS Blood and Transplant: Haemoglobin and iron; Lab Tests Online UK: Platelet count
Long-term conditions
- Coeliac disease, Crohn's or colitis, a stomach ulcer, or stomach or bowel surgery. Coeliac disease, bowel inflammation and stomach surgery reduce iron absorption or cause blood loss; coeliac disease is found in 3–5% of iron deficiency anaemia. BSG guidelines for the management of iron deficiency anaemia in adults (2021; PMID 34497146), statements 7 and 8, table 1
Some medicines and supplements can change this result too. When you add your results, Hea asks which ones you take.
What a GP reads it with
Ferritin
Read together with: Haemoglobin, CRP, Iron, Transferrin saturation. BSH guideline for the laboratory diagnosis of iron deficiency in adults and children (2022; PMID 34693519); BSG guidelines for the management of iron deficiency anaemia in adults (2021; PMID 34497146), Definitions; Lab Tests Online UK: Ferritin
A GP usually checks the full blood count with it, treats a deficiency with iron and looks for where the iron is going, especially in men and in women after the menopause.
Haemoglobin
Read together with: Ferritin, MCV (mean cell volume), Vitamin B12, Folate. Lab Tests Online UK: Full blood count (FBC); BSG guidelines for the management of iron deficiency anaemia in adults (2021; PMID 34497146)
A GP usually repeats the count with iron studies, asks about periods, diet and bowel symptoms, and investigates further in men and in women after the menopause.
Questions to ask your GP
- Should the cause be looked for, not just the level treated?
- When should this be repeated after treatment?
- Could inflammation be making this number look higher?
- Which tests are needed to find the cause?
- How does this compare with my previous count?
Safety first
If your lab or GP has flagged your result as urgent, follow their advice first.
Not for emergencies: call 999 or NHS 111.
Questions people ask
What is a ferritin blood test?
A ferritin test checks the amount of iron stored in your body. It is one of several blood tests the NHS uses to look at iron, along with a full blood count and a transferrin saturation test, which shows how much iron is in your blood.
NHS: Haemochromatosis – diagnosis, Page last reviewed 29 March 2023What are the symptoms of low iron?
The NHS lists tiredness and lack of energy, shortness of breath, noticeable heartbeats (palpitations), paler skin than usual and headaches as common symptoms of iron deficiency anaemia. Less common ones include ringing or buzzing in your ears (tinnitus), hair loss and restless legs. A GP will usually check with a full blood count.
NHS: Iron deficiency anaemia, Page last reviewed 26 January 2024What causes low ferritin?
The NHS says heavy periods and pregnancy are very common causes of iron deficiency. Bleeding in the stomach or intestines is another common cause, for example from an ulcer or from some anti-inflammatory painkillers. If the reason is not clear, the GP may do other tests to find it.
NHS: Iron deficiency anaemia, Page last reviewed 26 January 2024How do you increase your ferritin levels?
The NHS approach starts with your GP finding the reason your iron is low, such as heavy periods or bleeding in the gut. If you need iron supplements, take them as your GP or pharmacist advises. Iron-rich foods include dark-green leafy vegetables, meat, beans, peas and lentils, and dried fruit. Large amounts of tea, coffee, milk and dairy make it harder for your body to absorb iron.
NHS: Iron deficiency anaemia, Page last reviewed 26 January 2024What can cause a high ferritin level?
The NHS lists several causes of high iron in the body, including long-term liver disease, alcohol misuse, too much iron from supplements or injections, and an inherited condition called haemochromatosis. To check for haemochromatosis, doctors use ferritin with other blood tests and sometimes a gene test. If these find a problem, you are usually referred to a hospital specialist.
NHS: Haemochromatosis – diagnosis, Page last reviewed 29 March 2023Got your result? Start with this question in your AI.
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Sources
Each line about the test above names the guideline it comes from, as Hea's guide cites it. The answers to the questions come from:
- NHS: Haemochromatosis – diagnosis, Page last reviewed 29 March 2023
- NHS: Iron deficiency anaemia, Page last reviewed 26 January 2024