Low Ferritin: What It Means and What to Do Next
Short answer: ferritin shows how much iron your body has in storage. UK guidance uses a ferritin below 30 µg/L to confirm iron deficiency, even if your haemoglobin is still normal. Low ferritin is common and usually treatable, but the cause should always be found, especially in men and in women after the menopause.
What ferritin measures
Ferritin is the protein that stores iron. As iron runs low, ferritin falls first, often months before haemoglobin drops and anaemia shows on a full blood count. That makes ferritin the most useful single test for iron stores.
What counts as low ferritin?
Below 30 µg/L: iron deficiency, according to UK guidance.
Below 15 µg/L: severely depleted iron stores.
30 to 100 µg/L with inflammation: ferritin rises during infection or inflammation, so iron deficiency can still be present. A CRP and transferrin saturation help to tell.
The reference range printed on lab reports often starts lower than 30, so a result can look normal and still mean your stores are low.
Symptoms of low iron
Tiredness and low energy, breathlessness on exertion, headaches, feeling the cold, pale skin, brittle nails, hair shedding, restless legs and poor concentration. Some people have no symptoms at all.
Common causes
Heavy periods, the most common cause in women of childbearing age
Pregnancy and breastfeeding
Low iron intake, for example some vegetarian or vegan diets
Regular blood donation or endurance sport
Poor absorption, for example coeliac disease or after stomach surgery
Blood loss from the gut, which may not be visible
Important: iron deficiency without an obvious cause, particularly in men and in women after the menopause, should be investigated through your GP, because it can be the first sign of a problem in the bowel or stomach.
How low ferritin is treated
Treatment is usually iron tablets. UK guidance supports once-daily or alternate-day dosing, which is often better tolerated and absorbed than taking iron several times a day. Taking it with vitamin C, for example orange juice, and away from tea, coffee, milk and antacids helps absorption. Common side effects include constipation, stomach upset and dark stools.
Do not take iron long term without a test showing you need it, because too much iron can be harmful. Diet helps too: red meat, pulses, dark green vegetables and fortified cereals are good sources.
When to retest
If you were anaemic, haemoglobin should start to rise within a few weeks of treatment. Ferritin takes longer to refill, so a recheck after around three months, or as your clinician advises, shows whether your stores have recovered.
How we can help
Check your iron stores with a ferritin blood test, or the fuller iron status profile or anaemia profile.
Already have a low result? Book a clinician consultation with our Advanced Clinical Practitioner, by phone UK-wide from £50 or face to face in Crewe. We will explain your result, look for a likely cause and prescribe iron if it is right for you.
Frequently asked questions
Can I have low ferritin with normal haemoglobin?
Yes. This is called iron deficiency without anaemia. It can still cause symptoms and is still worth treating and investigating.
Can low ferritin cause hair loss?
Low iron stores are commonly linked with increased hair shedding, although the evidence is mixed. It is one reason ferritin is often checked when people notice thinning hair.
Do I need to fast for a ferritin test?
Not usually for ferritin alone. If serum iron or transferrin saturation is included, a morning sample is often preferred because iron levels vary through the day.
Related reading
This article is general information based on UK guidance from the NHS and NICE. It is not personal medical advice. If you have symptoms or are worried about a result, speak to a clinician.
