In short:
- Iron contributes in particular to a reduction of tiredness and fatigue, to normal cognitive function and to normal formation of red blood cells and haemoglobin, according to the EU register of claims.
- A deficiency most often comes from an insufficient dietary intake, blood loss (heavy periods) or digestive malabsorption.
- Tiredness, paleness and breathlessness are the most common signs; brittle nails, hair loss or restless legs can also appear.
- A blood test (ferritin) confirms a deficiency, sometimes even before anaemia appears: if in doubt, ask a doctor.
An iron deficiency sets in when the body no longer has enough of this mineral, which is essential for transporting oxygen and making red blood cells. It mostly affects certain identified profiles: women of childbearing age, pregnant women, growing children, people following a strict vegetarian diet. This fact sheet sets out the causes, the symptoms and what to do.
Iron deficiency at a glance
| Benchmark | Value or information |
|---|---|
| Authorised roles | Reduction of tiredness and fatigue, normal cognitive function, normal oxygen transport, normal formation of red blood cells and haemoglobin |
| Reference intake (ANSES), adult men and post-menopausal women | 11 mg a day |
| Reference intake (ANSES), women of childbearing age | 11 to 16 mg a day depending on menstrual losses |
| Dietary sources | Red meat, offal, fish and seafood, legumes, leafy green vegetables |
| Profiles most at risk | Women of childbearing age, pregnant women, children and teenagers, strict vegetarian diet, chronic digestive disease |
| Diagnosis | Blood test (ferritin, then haemoglobin if anaemia is suspected), made by a doctor |
What is iron and what is it for?
Iron is a mineral that the body cannot make and must obtain from food, or, to a small extent, recycle from red blood cells that have reached the end of their life. It is part of haemoglobin, the protein in red blood cells that carries oxygen to the tissues.
The EU register of claims1 recognises several authorised claims for iron. Iron contributes:
- to a reduction of tiredness and fatigue;
- to normal cognitive function;
- to normal energy-yielding metabolism;
- to normal formation of red blood cells and haemoglobin;
- to normal oxygen transport in the body;
- to the normal function of the immune system;
- and it has a role in the process of cell division.
Iron deficiency develops in stages: iron stores (ferritin) fall first, before red blood cell production is affected, then haemoglobin decreases in turn, down to anaemia.
The causes of an iron deficiency
An iron deficiency usually has one of these origins.
| Cause | What to know |
|---|---|
| Insufficient dietary intake | A diet low in meat, fish or legumes; a strict vegetarian or vegan diet without particular attention to iron sources |
| Blood loss | Heavy periods, digestive bleeding (ulcer, polyp, haemorrhoids), frequent blood donations |
| Digestive malabsorption | Coeliac disease, Crohn’s disease, Helicobacter pylori infection, stomach or duodenum surgery |
| Increased needs | Pregnancy, growth in children and teenagers, regular intensive sports practice |
Who is most at risk of an iron deficiency?
The US NIH fact sheet on iron2 lists several profiles more exposed to an insufficient intake or to greater iron loss.
| Profile | Why |
|---|---|
| Women of childbearing age, heavy periods | Menstrual iron losses greater than the usual dietary intake |
| Pregnant women | Increased needs for blood volume and foetal growth |
| Infants and young children | High needs relative to body weight, to support growth |
| Teenagers | Rapid growth, and heavy periods in teenage girls |
| People who eat no meat, poultry or seafood | Iron from plants is less well absorbed than iron from animal products |
| Chronic digestive diseases | Reduced intestinal absorption (coeliac disease, Crohn’s disease) |
The symptoms of an iron deficiency
The most common signs
An iron deficiency often sets in gradually, and the very earliest stages cause no noticeable symptoms. The most common signs, once the deficiency progresses to anaemia, are intense tiredness, weakness, paleness, breathlessness on exertion and headaches. Difficulty concentrating or remembering, and increased sensitivity to cold, can also appear2.
Less well-known signs
Other, less systematic signs are classically associated with iron deficiency: brittle or ridged nails, hair loss, a sore or inflamed tongue, restless legs syndrome, or unusual cravings for non-food substances (ice, dirt), known as pica. In children, an uncorrected iron deficiency can come with learning difficulties2. These signs have many other possible causes: only a blood test, interpreted by a doctor, can link them to an iron deficiency.
How do you know if you are short on iron?
A blood test can measure ferritin, the marker that reflects the body’s iron stores, and haemoglobin if anaemia is suspected. A ferritin level below 30 micrograms per litre suggests iron deficiency, and a level below 10 micrograms per litre suggests established iron deficiency anaemia2; haemoglobin and haematocrit, often used for screening, remain less sensitive and specific markers than ferritin3. It is the doctor who interprets these results, looks for the cause (dietary, blood loss, malabsorption) and decides on the appropriate treatment.
How to prevent or correct an iron deficiency
Dietary iron comes in two forms: haem iron, better absorbed, found in animal products, and non-haem iron, less well absorbed, found in plants.
| Food | Why it matters |
|---|---|
| Red meat and offal (black pudding, liver) | Haem iron, among the best absorbed |
| Fish and seafood (mussels, sardines) | A good source of haem iron |
| Legumes (lentils, chickpeas, beans) | A source of non-haem iron, better absorbed with vitamin C |
| Leafy green vegetables (spinach, chard) | A source of non-haem iron |
| Whole grains and nuts | Contribute to daily iron intake |
| Vitamin C-rich foods (citrus, bell pepper) | Help absorb non-haem iron eaten at the same meal |
For someone on a strict vegetarian or vegan diet, systematically pairing a vitamin C source with plant sources of iron improves absorption. The guide on micronutrition and diet explains how to spot the most common deficiencies depending on the diet followed, and the page on vitamin and mineral needs places iron among the other micronutrients.
Beyond diet, an existing deficiency is corrected under medical supervision: it is the doctor who chooses the form of supplement and the length of treatment based on the cause found. The page on vitamin B12 deficiency covers another common deficiency that shares some symptoms with iron deficiency, and the one on vitamin courses for tiredness covers other causes of tiredness worth watching.
Key takeaways
- Iron contributes in particular to a reduction of tiredness and fatigue, to normal cognitive function and to normal formation of red blood cells and haemoglobin.
- A deficiency most often comes from an insufficient dietary intake, blood loss or digestive malabsorption.
- Women of childbearing age, pregnant women, children and people on a strict vegetarian diet are the profiles most at risk.
- A blood test (ferritin) confirms a deficiency, sometimes even before anaemia appears: suggestive symptoms call for a medical opinion.
Frequently asked questions
What are the symptoms of an iron deficiency?
The most common signs are intense tiredness, paleness, breathlessness on exertion and headaches. Brittle nails, hair loss, restless legs or a sore tongue can also appear, especially when the deficiency progresses to anaemia.
What causes an iron deficiency?
The three most common causes are an insufficient dietary intake, blood loss (heavy periods, digestive bleeding) and digestive malabsorption (coeliac disease, Crohn’s disease, stomach surgery), which reduce absorption or increase iron needs.
Who is most at risk of an iron deficiency?
Women of childbearing age, especially with heavy periods, pregnant women, growing children and teenagers, people following a strict vegetarian or vegan diet, and people with a chronic digestive disease.
Can you be low on iron without being anaemic?
Yes, iron deficiency develops in stages: iron stores (ferritin) fall first, before haemoglobin decreases in turn. A low ferritin level can therefore coexist with still-normal haemoglobin, sometimes already with tiredness or other symptoms.
How do you know if you are short on iron?
A blood test can measure ferritin, which reflects the body’s iron stores, and haemoglobin if anaemia is suspected. If you have suggestive symptoms or a risk factor, the diagnosis and treatment decision are for a doctor to make.