Low ferritin on a blood test: what it means for your iron
Medically Reviewed by Dr. Pedro Yelamo Vera, MD
Licensed Physician No. 484814280 · Official Medical College of Bizkaia (Spain)Last reviewed: 21 October 2026
Low ferritin explained: what it says about your iron stores, why the cause matters as much as the number, who needs more tests, and warning signs.
You don't have to figure this out alone
Dr. Pedro Yelamo Vera is an independent, bilingual GP licensed in Spain. Book a 15-minute video consultation in English or Spanish for €50, with a private electronic prescription issued under Spanish law when clinically appropriate.
Ferritin is the most useful blood test for iron stores. A low ferritin means your iron reserves are running low, even if your haemoglobin is still normal. Finding out why is just as important as the number. This guide explains how to read the result and what usually happens next.
- Ferritin shows how much iron your body has stored. A low ferritin almost always means low iron stores.
- Many labs and UK guidance treat a ferritin under about 30 µg/L as a sign of iron deficiency in adults.
- Ferritin can look normal or high during infection or inflammation, even when iron is low.
- The cause matters. Heavy periods, diet and blood loss from the gut are common. Some people need tests to rule out a hidden cause.
Dr. Pedro Yelamo Vera is a GP licensed in Spain (Colegiado No. 484814280).
For a medical emergency, call 112 or go to the nearest local emergency department. Do not wait for a video consultation or an online reply.
What ferritin is
Ferritin is a protein that stores iron inside your cells. A small amount is in the blood. The level in the blood gives a good idea of how much iron you have in reserve.
Iron is needed to make haemoglobin, the part of red blood cells that carries oxygen. When stores run low, the body first uses up its reserves. Later, haemoglobin falls too. That is called iron deficiency anaemia.
On a Spanish report you will see ferritina, in ng/mL or µg/L. Both units give the same number.
How to read your result
Each lab sets its own range. Look at the one printed next to your result. As a guide for adults:
| Ferritin | What it often means |
|---|---|
| Under about 15 µg/L | Iron stores are very low |
| Under about 30 µg/L | Iron deficiency is likely, especially with symptoms |
| 30 to 100 µg/L with inflammation | Iron deficiency is still possible |
Ferritin also rises when the body is fighting infection or inflammation. In that case a "normal" ferritin can hide low iron. Your doctor may look at other tests, such as transferrin saturation (índice de saturación de transferrina) and CRP, a marker of inflammation.
Low ferritin with low haemoglobin means iron deficiency anaemia. Our guide to the full blood count explains haemoglobin and the red cell indices.
Symptoms of low iron
Some people feel fine. Others notice:
- Tiredness and lack of energy.
- Shortness of breath on effort, or a pounding heartbeat.
- Pale skin.
- Headaches.
- Hair loss or brittle nails.
- Restless legs at night.
- Cravings to eat ice or non-food items.
Why the cause matters
Low iron is a sign, not a diagnosis. The body loses iron through blood loss or does not take in enough. Common causes are:
- Heavy periods. This is the most common cause in women before the menopause.
- Pregnancy, when iron needs go up.
- Diet low in iron, for example some vegetarian or vegan diets without planning.
- Poor absorption, for example with coeliac disease or after stomach surgery.
- Blood loss from the gut, for example from ulcers, some pain medicines or, less often, bowel polyps or cancer.
- Frequent blood donation or hard endurance training.
In men, and in women after the menopause, iron deficiency without a clear cause needs further tests. UK guidance from NICE advises checking the gut in many of these cases. Your doctor will explain what is right for you.
Have an iron or ferritin result you are not sure about?
You can book a video visit to go through the results you already have with a GP licensed in Spain, in English or Spanish.
What usually happens next
Your doctor will look at your ferritin together with your symptoms, history and other results. Common next steps are:
- Check haemoglobin and the red cell indices, if not already done.
- Ask about periods, diet, digestion and any blood loss.
- Test for coeliac disease, often with a simple blood test.
- Arrange gut tests if the cause is not clear, especially in men and after the menopause.
- Agree a plan to restore iron, and when to repeat the blood test.
Do not start strong iron supplements for months without a plan. Too much iron can be harmful. Iron also hides the clues your doctor needs to find the cause. Ask first.
When to get urgent help
Call 112 or go to an emergency department if you have:
- Black, tarry stools, or a lot of blood from the back passage.
- Vomiting blood.
- Chest pain, fainting or severe shortness of breath.
- Very heavy bleeding from the vagina, especially if you feel faint.
Going through your results by video
Dr. Yelamo is a GP licensed in Spain. He can go through results you already have, by video, for adults. Visits run every day, 07:30–20:30 (Spain time). In the visit he will:
- Read the full report, with units, dates and the lab's range.
- Compare it with past results, including ones from other countries.
- Ask about periods, diet, digestion, medicines and symptoms.
- Explain what your ferritin means and what is usually checked next.
- Tell you if you need a test or an exam in person.
He does not promise any test or prescription before the visit. Where clinically appropriate, following a genuine evaluation. Treatment and prescriptions are issued solely at the doctor's discretion based on evidence-based clinical guidelines.
See how the Urgent Care video visit works. It lasts 15 minutes and costs €50.
Frequently asked questions
What ferritin level is too low?
Each lab has its own range. In adults, a ferritin under about 30 µg/L usually points to iron deficiency, and under 15 µg/L to very low stores. Inflammation can raise ferritin and hide low iron.
Can I have low ferritin with normal haemoglobin?
Yes. Iron stores fall first. Haemoglobin drops later. Low ferritin with normal haemoglobin is iron deficiency without anaemia, and it can still cause tiredness.
Why is low iron sometimes checked with gut tests?
Because slow blood loss from the gut can cause it without other signs. In men and in women after the menopause, guidance often advises gut tests when there is no clear cause.
Should I take iron tablets if my ferritin is low?
Talk to a doctor first. Iron is not right for everyone, too much can be harmful, and it can hide the clues that show the cause.
Can an online GP go through my ferritin result?
Yes. Dr. Yelamo can go through results you already have by video, for adults. He explains them and tells you if you need more tests or an exam in person.
Sources
- NHS: Iron deficiency anaemia
- NHS: Iron deficiency anaemia, causes
- NHS: Iron deficiency anaemia, diagnosis
- NHS: Total iron-binding capacity (TIBC) and transferrin test
- NICE guideline NG12: Suspected cancer, recognition and referral
Related guides
Medical Citations & Sources
This content is written and reviewed by a licensed physician with reference to the following official health authorities.
