Iron Deficiency and Iron-Deficiency Anemia: Causes, Symptoms and Diagnosis
What iron deficiency and iron-deficiency anemia are, common causes such as heavy periods and bleeding, symptoms that overlap with other conditions, and how clinicians diagnose it.
Content last updated . This page has not been medically reviewed.
How the sources define the terms
Anemia is a condition in which the body does not have enough healthy red blood cells. Iron-deficiency anemia is the type that develops when the body's iron stores run low, and it is the most common form of anemia. [2] NHLBI describes it the same way: a type of anemia that develops if you do not have enough iron in your body. [4] Low iron can exist before anemia appears. The NHS says there are other types of anaemia, such as vitamin B12 or folate deficiency, that the blood test also checks for. [1]Evidence labels on this page: established means standard clinical practice described by health agencies; insufficient or Proper evidence not found means we looked and could not support a claim.
Common causes
Finding the cause matters as much as replacing the iron. The sources we read group causes like this.| Cause | What the source says | Source |
|---|---|---|
| Heavy periods | Heavy, long or frequent menstrual periods are a common cause of iron loss through bleeding. | [2] |
| Pregnancy and breastfeeding | Heavy periods and pregnancy are very common causes; in pregnancy it is most often a lack of iron in the diet. The body also needs more iron than normal when pregnant or breastfeeding. | [1][2] |
| Bleeding in the digestive tract | Ulcers, bowel or food-pipe inflammation, piles and (less often) cancers, and regular use of NSAIDs such as ibuprofen and aspirin. | [1] |
| Poor absorption | Celiac disease, Crohn disease, gastric bypass surgery. | [2] |
| Low intake | Not eating enough iron-containing foods, for example on a strict vegetarian diet. | [2] |
| Other | Long-lasting inflammation conditions such as heart failure or obesity can make it hard for the body to regulate and use iron. | [4] |
Endurance sports can also cause athletes to lose iron through the digestive tract and through the breakdown of red blood cells. [4] Frequent blood donors are also listed as at risk. [5]
Young children can become iron deficient when they do not get enough iron in their diet, often as they move to whole foods around 9 months to 1 year. [4] Infants are born with enough iron to last about six months, according to MedlinePlus. [5]
Symptoms
The NHS lists tiredness and lack of energy, shortness of breath, noticeable heartbeats, paler than usual skin and headaches. [1] Less common ones include wanting to eat non-food items such as paper or ice (pica). [1] NHLBI notes that people with mild or moderate iron-deficiency anemia may not have any symptoms. [4]None of these symptoms is specific to low iron. The pages we read point to a blood test, not symptoms, as the way to check.
How it is diagnosed
The NHS says a GP will usually do a full blood count to find out whether the number of red blood cells is normal, and if the reason is unclear may do other tests such as a stool test for blood. [1] MedlinePlus lists a complete blood count, serum iron, total iron binding capacity and serum ferritin, and, to check for blood loss, tests that may include colonoscopy and upper endoscopy. [2] What each test measures is explained on Iron tests explained.Treatment is clinician-led
The NHS says that once the reason has been found the GP will recommend treatment; if the blood test shows a low red cell count, iron tablets will be recommended, usually for about 6 months. [1] MedlinePlus says most of the time a provider will measure your iron level before you start supplements. [2] Do not treat a suspected deficiency alone: the cause has to be found, and iron supplements are not appropriate for everyone (see Iron overload and hemochromatosis).What is not established
Proper evidence not found in the pages we read for diagnosing iron deficiency from hair analysis or at-home panels (searched NHS, MedlinePlus, NHLBI). For the limits of such tests see Hair mineral analysis.If left untreated
The NHS says untreated iron deficiency anaemia can raise the risk of illness and infection, may increase the risk of heart or lung complications, and in pregnancy can raise the risk of complications before and after birth. [1]More on supplements is on Iron, heavy periods and iron on Iron for athletes, heavy periods and blood donors, and everyday context on Anemia and iron deficiency.
Frequently asked questions
Can I tell I am iron deficient from symptoms alone?
No. Tiredness, breathlessness and pale skin overlap with many conditions, and the NHS says a GP usually confirms anaemia with a blood test. [1]
Why do clinicians look for a cause?
Bleeding, for example from ulcers or heavy periods, and poor absorption are common causes, and treatment depends on what is found. [1][2]
Are heavy periods enough to cause anemia?
The NHS lists heavy periods as a very common cause of iron deficiency anaemia, and notes that heavy periods can be treated with medicine. [1] Talk to a GP about heavy periods. [6]
Can I have low iron without anemia?
Yes. MedlinePlus notes that not all people who have low iron levels have anemia. [7]
Do iron supplements fix it quickly?
MedlinePlus says anemia often improves with about 6 weeks of iron therapy, with iron continuing about 6 months more to replace stores; a clinician guides this. [2]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
When to see a clinician
References
- NHS (UK). Iron deficiency anaemia. Page last reviewed 26 January 2024. Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Iron deficiency anemia. Review date 4/1/2025. Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Iron overdose. Read 2026-10-23.
- NHLBI (US National Institutes of Health). Iron-deficiency anemia. Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Iron in diet. Review date 1/21/2025. Read 2026-10-23.
- NHS (UK). Heavy periods. Page last reviewed 19 September 2024. Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). Iron tests. Read 2026-10-23.