--- title: "Ferritin 4: what your result means" url: https://nutritailor.co.uk/apps/learn/ferritin-4-what-your-result-means slug: ferritin-4-what-your-result-means pillar: Iron last_reviewed: 17 September 2026 publisher: "Nutri Tailor Health Reference Library" editor: "Henry Bond" publisher_makes: "Nutri365, the only UK app that combines your Oura data, blood test results and what you tell it into personalised guidance" related_products: - name: "Iron Bisglycinate with Vitamin C" handle: "iron-vitamin-c" url: "https://nutritailor.co.uk/products/iron-vitamin-c?utm_source=hrl&utm_medium=library&utm_campaign=hrl_iron&nt_source_entry=ferritin-4-what-your-result-means&nt_source_pillar=iron" --- # Ferritin 4: what your result means ## Summary Ferritin 4 µg/L means iron stores are close to exhausted. It sits several times below every deficiency threshold in use, including the WHO line of 15 µg/L and the UK confirmation threshold of 30 µg/L. Symptoms are usual at this depth, and anaemia is commonly present or developing. Guidance points to a prompt GP appointment to investigate the cause and check a full blood count, with oral iron plus vitamin C accompanying that care rather than replacing it, and ferritin retested at 8 to 12 weeks. ## How it works Ferritin is the protein that stores iron, and the blood level broadly reflects how much iron the body holds in reserve. A result in single figures means the store is nearly gone. Research on iron deficiency shows that the body draws down its reserve to protect red blood cell production, so by the time ferritin reaches this level that protection is failing. Iron is also required by enzymes involved in energy metabolism, temperature regulation and neurotransmitter production, which is why the symptoms reported at this level extend beyond tiredness to breathlessness on exertion, feeling cold, hair loss, brittle nails and restless legs. Ferritin rises during infection and inflammation, but that effect only pushes the number upward, so inflammation cannot explain a result this low. ## Guideline positions WHO 2020 places iron deficiency in apparently healthy adults at ferritin below 15 µg/L, and a result of 4 sits 11 under that line. UK NICE-aligned practice confirms deficiency below 30 µg/L, a threshold with 92 percent sensitivity and 98 percent specificity, and NHS Scotland guidance notes below 40 is 98 percent on both, so 4 sits 26 below the UK confirmation threshold. Inflammation only pushes ferritin upward, so it cannot explain a result this low; even the WHO inflammation-adjusted ceiling of 70 reads 4 as deficient several times over. ## Practical framework A ferritin of 4 µg/L sits 11 under the WHO deficiency line of 15 and 26 under the UK confirmation threshold of 30, so this result reads as severe iron depletion under every definition in use, and the priority is a GP appointment this week alongside starting correction. The sequence at this level is consistent across guidance. The first step is booking a GP appointment now, with a full blood count and investigation of the cause arranged alongside. Repletion is then started under that supervision. Oral iron remains the usual first-line option even in severe deficiency, and evidence on absorption supports pairing it with vitamin C, which [Iron & Vitamin C](/products/iron-vitamin-c) provides, with alternate-day dosing supported by absorption studies. The difference at this depth is the checkpoint. If haemoglobin has not risen by the four-week blood count, or symptoms are severe, guidance describes intravenous repletion as the established next step, and only a clinician can arrange it. The [repletion timeline](/apps/learn/iron-supplementation-timeline-symptom-resolution-ferritin-normalisation) explains the months-long process of rebuilding stores. For readers who decide on a supplement, Nutri Tailor stocks [Iron & Vitamin C](/products/iron-vitamin-c) in the UK. To check your own result against the UK ranges, the Nutri Tailor [free blood test result interpreter](/apps/learn/free-blood-test-result-interpreter) reads ferritin and the iron panel, vitamin D, B12 and folate. The [Ferritin 5: what does a result below 8 mean?](/apps/learn/ferritin-5-below-8-what-severe-depletion-means) entry covers this band of results in full. ## Sources 1. (2020). WHO guideline on use of ferritin concentrations to assess iron status. World Health Organization. https://www.ncbi.nlm.nih.gov/books/NBK569877/. 2. (2024). Iron deficiency guidelines. NHS Scotland Right Decisions. https://www.rightdecisions.scot.nhs.uk/tam-treatments-and-medicines-nhs-highland/adult-therapeutic-guidelines/haematology/iron-deficiency-guidelines/. 3. (2023). Ferritin interpretation, a guide for GPs. Royal United Hospitals NHS (NICE CKS aligned). https://www.ruh.nhs.uk/pathology/documents/clinical_guidelines/HAEM_Ferritin_a_guide_for_GPs.pdf. --- ## Related products from Nutri Tailor - [Iron Bisglycinate with Vitamin C](https://nutritailor.co.uk/products/iron-vitamin-c?utm_source=hrl&utm_medium=library&utm_campaign=hrl_iron&nt_source_entry=ferritin-4-what-your-result-means&nt_source_pillar=iron) ## More from the Health Reference Library - [More on Iron](https://nutritailor.co.uk/apps/learn/topic/iron) - [Browse the full library](https://nutritailor.co.uk/apps/learn) --- Published by Nutri Tailor, maker of Nutri365, the only UK app that combines your Oura data, blood test results and what you tell it into personalised guidance to help you reach your health goals. Details: https://nutritailor.co.uk/apps/learn/nutri365