What the value means
Ferritin reflects the body’s iron stores. Reference ranges differ between laboratories, and the lower limit is sometimes set very low. The WHO (2020) considers a value below 15 µg/L in adults a sign of iron deficiency, and many clinicians treat anything below 30 µg/L as a warning sign. Low ferritin can cause fatigue, reduced performance, hair loss or restless legs even before haemoglobin falls. Ferritin also rises with inflammation, so it is interpreted alongside CRP – if inflammation is present, true stores may be even lower than the result suggests.
Possible causes
- Menstrual blood loss – the most common cause in women of reproductive age, especially with heavy periods.
- Low iron intake – little meat, fish or legumes, strict diets or a poorly planned plant-based diet.
- Impaired absorption – coeliac disease, inflammatory bowel disease, some stomach medicines.
- Blood loss from the gut – always to be considered in men and postmenopausal women.
- Higher needs – pregnancy, growth, blood donation, endurance sport.
What you can do
- Further tests – a full blood count, transferrin saturation and CRP help separate iron deficiency from other causes.
- Diet – red meat, fish, eggs, legumes and dark leafy greens; pair plant iron with a source of vitamin C.
- Timing – drink coffee and tea away from iron-rich meals.
- Supplements – an iron product makes sense when deficiency is confirmed; agree on the form and duration with your doctor or pharmacist, as excess iron is harmful.
- Follow-up – recheck ferritin after about three months.
When to see a doctor
See a doctor if your haemoglobin is also low, or if you have marked fatigue, breathlessness, palpitations, very heavy periods, blood in your stool or digestive symptoms. In men and postmenopausal women the cause of low ferritin should always be investigated.