Quick answer: Ferritin is the protein that stores iron, and a low result usually means your iron reserves are running low. Blood loss and low intake are common causes, but when ferritin stays low despite supplements, the gut is often part of the picture: coeliac disease, H. pylori, low stomach acid, acid-suppressing medicines and gut inflammation can all reduce iron absorption. Your doctor should look for the cause, especially if you are a man or post-menopausal. Food choices, timing and, where appropriate, an individualised supplement plan may support absorption.
“My ferritin is low again” is something I hear often, usually from people who are tired, losing more hair than usual, or who have been taking iron for months with little change. Low iron frequently travels with digestive symptoms, and the two are more connected than most people realise. If tiredness after meals is also part of your story, have a look at brain fog and fatigue after eating.
What does low ferritin mean?
Ferritin is the main storage form of iron in the body, and the blood level broadly reflects how full your iron reserves are. A low ferritin is the most specific single marker of iron deficiency.1 It often drops before haemoglobin does, so you can have low ferritin with a “normal” full blood count.
One important nuance: ferritin also rises with inflammation or infection. A normal ferritin in someone with active inflammation can therefore hide a deficiency, which is why your doctor may look at it alongside transferrin saturation, CRP and other markers. Laboratory ranges vary, so always ask how your result was interpreted.
What are the symptoms of low ferritin?
Symptoms are commonly associated with low iron stores even before anaemia develops, and may include:
- tiredness and low stamina
- increased hair shedding and brittle nails
- breathlessness on exertion or a racing heart
- feeling cold, restless legs at night
- poor concentration
These are not specific to iron, so they should not be used to guess your level – a blood test is the only way to know.
Why is my ferritin low when I eat well?
There are broadly three reasons iron runs low: losing more than you take in (heavy periods, blood loss from the gut, frequent blood donation), not taking enough in, or not absorbing what you eat. When diet looks fine and ferritin still will not move, absorption becomes the key question.
Iron is absorbed mainly in the upper small intestine (the duodenum), and it needs an acidic stomach to be converted into a form the gut can take up. Anything that affects the stomach or the lining of the upper small intestine can therefore affect iron.
Which gut problems affect iron absorption?
- Coeliac disease: damages the lining where iron is absorbed. A meta-analysis found that around 3% of people with iron deficiency anaemia had biopsy-confirmed coeliac disease – higher than in the general population.4 UK guidelines recommend coeliac blood tests for adults with iron deficiency anaemia.2
- H. pylori: consistently associated with iron deficiency, likely through reduced stomach acid and small blood losses.5 See what an H. pylori positive result means.
- Autoimmune or atrophic gastritis: reduces stomach acid and is a recognised cause of iron deficiency that does not respond to tablets.3
- Acid-suppressing medicines (PPIs and similar), used long-term, can reduce iron absorption – never stop them without speaking to your doctor.
- Inflammatory bowel disease and gut surgery can affect both absorption and blood loss.
Haematology guidance recommends looking for coeliac disease, H. pylori and autoimmune gastritis when iron deficiency is unexplained or does not respond to oral iron.3
When to see your doctor first
- Black stools, blood in the stool or rectal bleeding
- Iron deficiency in a man or a post-menopausal woman (guidelines recommend gut investigation)
- Unintended weight loss or a change in bowel habit
- Very heavy periods, breathlessness at rest or chest pain
- Ferritin that keeps falling despite supplements
How can I improve my ferritin levels?
First, make sure the cause has been looked for – topping up without knowing why iron is low can delay finding something important. Alongside your doctor's plan, these food and lifestyle steps may support absorption:
- Combine iron-rich foods well: haem iron from meat, fish and seafood is absorbed more efficiently; plant iron (pulses, dark leafy greens, seeds) is better absorbed with vitamin C-rich foods such as peppers, citrus or kiwi in the same meal.
- Watch the timing of tea, coffee and calcium: they can reduce iron absorption when taken with an iron-rich meal or supplement.
- Supplement timing: a study in iron-depleted women found that giving iron on alternate days increased the fraction absorbed compared with consecutive days, likely because of the iron-regulating hormone hepcidin.6 Dose, form and schedule should be individualised with your doctor.
- Support the gut itself: addressing reflux, gut inflammation or an underlying condition with your medical team is often what finally lets iron rise.
Ferritin still stuck despite doing everything right?
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Book your free 15-minute call →Why do iron tablets upset my stomach?
Constipation, nausea, cramps and dark stools are common with oral iron, and they are one of the main reasons people stop taking it. Taking iron with a little food, changing the form or adjusting the schedule (with your doctor or pharmacist) may improve tolerance. Persistent gut symptoms on iron are worth mentioning rather than pushing through.
Frequently asked questions
What is a low ferritin level?
Laboratories use different ranges, and the threshold depends on context, such as inflammation. Your doctor will interpret your ferritin together with haemoglobin, transferrin saturation and CRP.
Can gut problems cause low ferritin?
Yes. Coeliac disease, H. pylori, atrophic gastritis, inflammatory bowel disease and long-term acid-suppressing medicines are all associated with reduced iron absorption or gut blood loss.
How long does it take to raise ferritin?
It varies with the cause, the dose and absorption. Iron stores usually rebuild over months rather than weeks, and your doctor will recheck your levels to see how you are responding.
Should I take iron every day or every other day?
Some research suggests alternate-day dosing can improve the fraction of iron absorbed. The right dose and schedule depend on your situation and should be agreed with your doctor.
Does coffee affect iron absorption?
Coffee and tea contain polyphenols that can reduce non-haem iron absorption when consumed with a meal or supplement. Having them between meals may help.
References
- Camaschella C. Iron-deficiency anemia. N Engl J Med. 2015. PubMed: PMID 25946282
- Snook J, et al. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut. 2021. PubMed: PMID 34497146
- Hershko C, Camaschella C. How I treat unexplained refractory iron deficiency anemia. Blood. 2014. PubMed: PMID 24215034
- Mahadev S, et al. Prevalence of celiac disease in patients with iron deficiency anemia – a systematic review with meta-analysis. Gastroenterology. 2018. PubMed: PMID 29689265
- Hudak L, et al. An updated systematic review and meta-analysis on the association between Helicobacter pylori infection and iron deficiency anemia. Helicobacter. 2017. PubMed: PMID 27411077
- Stoffel NU, et al. Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women. Lancet Haematol. 2017. PubMed: PMID 29032957
This article is for educational purposes and is not medical advice. Nutritional therapy does not replace medical care. Always work with your doctor for any persistent or new symptoms and before making changes to your care, medication or supplements.