Ferritin
| Clinical | Optimal | |
|---|---|---|
| Male | 30 - 400 ug/L | 30-300 ug/L (optimal 40-150 ug/L) |
| Female | 13 - 150 ug/L | 13-150 ug/L (optimal 40-100 ug/L) |
What is Ferritin?
Ferritin is a protein complex that stores iron inside your cells, primarily in the liver, spleen, and bone marrow. It acts as your body's iron reserve, releasing iron in a controlled manner when needed for essential processes such as red blood cell production, oxygen transport, energy metabolism, and immune function.
Measuring blood ferritin provides the most reliable single indicator of your total body iron stores. Low ferritin is the earliest detectable sign of iron deficiency, often appearing before other iron markers become abnormal and well before anaemia develops. This makes it an invaluable early warning marker.
It is important to note that ferritin is also an acute phase reactant, meaning it rises during inflammation, infection, or illness. This can temporarily mask iron deficiency, as ferritin may appear normal or even elevated despite depleted iron stores. Interpreting ferritin alongside other iron markers and inflammatory markers gives the most accurate picture.
Why Ferritin Matters for Your Health
Iron deficiency is the most common nutritional deficiency worldwide and is particularly prevalent among women of reproductive age, vegetarians, vegans, and endurance athletes in the UK. Symptoms can develop gradually and are often dismissed as normal tiredness, including fatigue, weakness, poor concentration, hair loss, cold intolerance, and reduced exercise tolerance.
From a longevity perspective, both iron deficiency and iron overload are harmful. Insufficient iron impairs oxygen delivery, energy production, and immune function. Conversely, excess iron acts as a pro-oxidant, generating free radicals that damage cells and tissues, accelerating ageing and increasing the risk of liver disease, heart disease, and certain cancers.
Maintaining ferritin within an optimal range, not simply above the minimum, is an important aspect of health optimisation. Many longevity-focused clinicians target a ferritin level that reflects adequate stores without excess, typically between 40-100 ug/L for most individuals.
Ferritin& Your Wearable Data
Ferritin reflects your body's total iron stores and is the single most useful test for diagnosing iron deficiency. Wearable data can reveal patterns associated with low ferritin before symptoms become obvious. Declining VO2 max estimates, elevated heart rate during previously easy exercise, and reduced exercise capacity all correlate with falling ferritin levels, as iron is essential for oxygen transport via haemoglobin.
Athletes and highly active individuals tracked by wearables are at increased risk of iron depletion. High training volumes, visible in your wearable's exercise data, accelerate iron loss through sweat, gastrointestinal blood loss from impact sports, and increased red blood cell turnover. Wearable data showing high weekly training loads alongside declining performance metrics should prompt ferritin testing.
Ferritin is also an acute-phase reactant that rises during inflammation. If your wearable data shows signs of overtraining or illness (elevated resting heart rate, decreased HRV, disrupted sleep), a normal or elevated ferritin reading may mask underlying iron deficiency. Context from your wearable helps clinicians interpret ferritin more accurately.
What High Ferritin May Suggest
Elevated ferritin can result from iron overload, inflammation, or both. True iron overload is most commonly caused by hereditary haemochromatosis, a genetic condition affecting approximately 1 in 200 people of Northern European descent, where the body absorbs too much dietary iron over time.
However, the most common reason for elevated ferritin in clinical practice is not iron overload but rather inflammation, metabolic syndrome, fatty liver disease, or alcohol consumption. In these cases, ferritin is elevated as part of the inflammatory response, and other iron markers (transferrin saturation) remain normal.
Persistently high ferritin with elevated transferrin saturation should raise suspicion for haemochromatosis, which is easily manageable if caught early but can cause serious organ damage (liver cirrhosis, diabetes, heart failure) if left untreated. Genetic testing is available and is recommended for individuals with persistently elevated ferritin.
What Low Ferritin May Suggest
Low ferritin is the earliest marker of depleted iron stores and indicates that your body's iron reserves are running low. Even before anaemia develops, low ferritin can cause symptoms including fatigue, poor concentration, exercise intolerance, hair thinning, restless legs, and increased susceptibility to infections.
The most common causes of low ferritin include inadequate dietary iron intake (particularly in vegetarians and vegans), blood loss (heavy menstrual periods, gastrointestinal bleeding), increased demand (pregnancy, intense exercise), and malabsorption (coeliac disease, inflammatory bowel disease, gastric surgery).
Many UK laboratories set the lower limit of ferritin at 13-15 ug/L, but symptoms of iron deficiency commonly occur at levels well above this. Most experts consider ferritin below 30 ug/L as indicative of depleted stores warranting intervention, regardless of whether formal anaemia criteria are met.
How to Optimise Your Ferritin
Food
Include haem iron sources such as red meat, liver, and shellfish, which are absorbed 2-3 times more efficiently than plant-based iron, Pair non-haem iron sources (lentils, beans, spinach, fortified cereals) with vitamin C-rich foods (citrus, peppers, tomatoes) to enhance absorption, Avoid drinking tea or coffee with meals, as the tannins and polyphenols significantly inhibit iron absorption, Include iron-fortified foods such as breakfast cereals and bread, which contribute meaningfully to UK dietary iron intake, Cook with cast iron cookware, which can increase the iron content of food, particularly acidic dishes
Lifestyle
Address any underlying causes of blood loss with your GP, particularly heavy menstrual periods or gastrointestinal symptoms, If following a vegetarian or vegan diet, be particularly mindful of iron-rich food choices and absorption-enhancing strategies, For endurance athletes, be aware that intense training increases iron losses through sweat, foot-strike haemolysis, and inflammation, Consider screening for coeliac disease if ferritin remains low despite adequate dietary intake, as this common condition impairs iron absorption
Supplements
Iron bisglycinate (20-30mg daily) is a well-absorbed form of supplemental iron with fewer gastrointestinal side effects than other forms, Take iron supplements with vitamin C (200-500mg) to enhance absorption, and away from tea, coffee, dairy, and calcium supplements, Lactoferrin (100-250mg daily) has been shown to improve iron absorption and may be better tolerated than standard iron supplements
⚠️ Supplement Warning
Warning: Do not self-supplement iron without medical guidance. Iron overload (haemochromatosis) is a serious condition affecting approximately 1 in 200 people of Northern European descent. Excess iron accumulates in the liver, heart, and pancreas, causing irreversible organ damage. Iron supplements should only be taken when blood tests confirm deficiency and under medical supervision. High-dose iron can also cause gastrointestinal side effects, interact with other medications, and mask serious underlying conditions such as gastrointestinal bleeding or coeliac disease.
When to Speak to Your GP
See your GP if your ferritin results suggest levels below 30 ug/L, particularly if you are experiencing fatigue, hair loss, or other symptoms of iron deficiency. Seek prompt medical advice if ferritin is below 15 ug/L, as this indicates significantly depleted stores. Also consult your GP if ferritin is persistently above 300 ug/L (men) or 200 ug/L (women), as this may warrant investigation for haemochromatosis or other underlying conditions. Unexplained iron deficiency, particularly in men or post-menopausal women, requires investigation to exclude gastrointestinal blood loss.
References
- WHO. Serum ferritin concentrations for the assessment of iron status. Geneva: WHO; 2011. who.int
- NHS. Iron deficiency anaemia — Diagnosis. Updated 2024. nhs.uk
- NICE. Anaemia — Iron deficiency. Clinical Knowledge Summaries. nice.org.uk
- Lancet. Camaschella C. Iron-deficiency anemia. N Engl J Med. 2015;372(19):1832-1843. pubmed.ncbi.nlm.nih.gov
- BMJ. Goddard AF, et al. Guidelines for the management of iron deficiency anaemia. Gut. 2011;60(10):1309-1316. pubmed.ncbi.nlm.nih.gov
Medical Disclaimer— This content is for general educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Omniwo Ltd is a wellness information service and is not a medical device, clinical laboratory, or regulated healthcare provider under MHRA guidelines. The “optimal ranges” presented on this page are based on published clinical guidelines (WHO, NICE, NHS) and peer-reviewed research; they represent functional wellness targets and may differ from standard laboratory reference ranges. Individual results should always be interpreted by a qualified healthcare professional (such as your GP) who understands your full medical history. Do not start, stop, or change any medication or supplement based solely on this information. If you are experiencing symptoms, seek medical attention promptly.