--- title: "Ferritin 5: what does a result below 8 mean?" url: https://nutritailor.co.uk/apps/learn/ferritin-5-below-8-what-severe-depletion-means slug: ferritin-5-below-8-what-severe-depletion-means pillar: Iron last_reviewed: 22 August 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-5-below-8-what-severe-depletion-means&nt_source_pillar=iron" --- # Ferritin 5: what does a result below 8 mean? ## Summary Ferritin below 8 µg/L indicates iron stores are close to exhausted. A result at this level 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, because the cause needs investigating, a full blood count is needed alongside, and severe deficiency sometimes warrants clinically supervised repletion, including intravenous iron where oral iron fails or speed matters. Oral iron with vitamin C remains part of the picture, but at this level it accompanies GP care rather than replacing it. ## 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. ## Timing Studies of iron repletion show recovery happens in stages. Haemoglobin responds first, and the four-week full blood count is the checkpoint, with a rise of around 20 g/L expected. Symptoms typically improve across weeks one to eight. Stores rebuild last, and ferritin is only meaningfully re-read at around 12 weeks, with full rebuilding taking months. NHS guidance describes continuing iron for around three months after resolution, aiming for a ferritin above 50 µg/L, with periodic monitoring where the cause persists. ## Safety profile Certain features alongside a very low ferritin need a GP the same week. These include black or bloody stools, unexplained weight loss, chest symptoms or breathlessness at rest, difficulty swallowing, and pregnancy. Severe anaemia occasionally needs urgent care, and breathlessness at rest or chest pain is a reason to call emergency services rather than book an appointment. Iron supplements are contraindicated in haemochromatosis, an inherited iron overload condition, and need storing out of reach of children. ## Special populations In menstruating women, a result this low usually reflects years of accumulating deficit, and clinical attention to the bleeding itself matters, because supplementation cannot keep pace with an unaddressed heavy loss. In men and in post-menopausal women, guidance regards single-figure ferritin as a finding that needs investigation for gastrointestinal causes as a priority. In pregnancy, a result at this level needs clinical contact the same week. Anyone who donates blood frequently, follows a restrictive diet, or has a gut condition such as coeliac disease should mention it at the appointment, because it helps identify the cause sooner. ## Guideline positions A result below 8 µg/L sits under every threshold in use. The WHO defines deficiency in healthy adults below 15 µg/L, and sets an inflammation-adjusted ceiling of 70 µg/L. UK practice aligned with NICE guidance confirms deficiency below 30 µg/L. NHS guidance for severe deficiency describes prompt investigation of the cause, a full blood count four weeks after starting iron to confirm the response, with a haemoglobin rise of around 20 g/L expected, and intravenous iron as the route clinicians consider where oral iron fails, is not tolerated, or speed is required. ## Practical framework 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. ## 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-5-below-8-what-severe-depletion-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