Why are my iron levels low?
Usually blood loss, or too little iron getting in. Heavy periods and pregnancy are very common causes. But in men and after the menopause, the cause is often hidden, so a GP looks for it.
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What counts as low iron levels?
Low iron usually means a low ferritin. That’s the blood test for your iron stores.
A ferritin below 30 µg/L generally means low stores. Below 15 means your stores are empty.
Think of ferritin as your iron savings. You spend them first, so your blood count can still look normal for a while. See low ferritin with normal haemoglobin.
Once the savings run out, haemoglobin (the part of red blood cells that carries oxygen) falls. That’s anaemia: below 130 g/L in men, or below 120 g/L in women who aren’t pregnant (over age 15).
- Below 15 µg/LBSG: iron stores empty.
- 15 to just under 30 µg/LBSG: generally low stores.
- 30 up to 150 µg/LInflammation can hide low iron here.
- Above 150 µg/LLow iron unlikely, even with inflammation.
Source: BSG guideline
An inflammatory illness can push ferritin up and hide low iron. Other iron tests help then.
Lab lower limits vary from 15 to 30, so check the range on your results. Our iron studies guide explains each line.
What causes low iron?
Blood is rich in iron. So losing blood, even slowly, is a common cause. Taking in too little is the other.
| Cause | Examples | Worth asking about if you |
|---|---|---|
| Heavy periods | Changing a pad or tampon every 1 to 2 hours, or clots bigger than a 10p coin. | have periods. |
| Pregnancy | Most often too little iron in the diet. | are pregnant. |
| Bleeding in the gut | Ibuprofen or aspirin, stomach ulcers, piles, an inflamed bowel. Less often, bowel or stomach cancer. | are a man, are past the menopause or take ibuprofen or aspirin. |
| Not absorbing iron | Coeliac disease, stomach surgery. Long-term acid tablets (PPIs) may also play a part. | have had stomach surgery or take PPIs. |
| Too little iron in food | Iron from plants is absorbed less well than iron from meat. | eat a vegan diet. |
| Other | Giving blood, nosebleeds, endurance sport. | give blood or train for long events. |
Sources: NHS; NHS heavy periods; NHS vegan diet; BSG guideline
Low iron often has more than one cause.
Coeliac disease, where gluten damages the gut, is found in 3% to 5% of people with iron deficiency anaemia. So UK gut doctors say everyone with iron deficiency anaemia should be tested for it.
Women aged 19 to 49 need 14.8mg of iron a day, against 8.7mg for men. Heavy periods raise the risk of iron deficiency anaemia. See periods and iron levels.
Take ibuprofen, aspirin or acid tablets? Ask your GP if they could play a part. Never stop or change a prescribed medicine without your prescriber.
Why do men get low iron levels?
Men don’t lose blood each month, and nor do women past the menopause. So UK gut doctors say their iron deficiency anaemia is often from hidden, slow bleeding in the gut.
In UK adults over 50 with this anaemia, about 1 in 3 have a bleeding problem, most often in the stomach or lower bowel. About 1 in 3 of those turns out to be a cancer. Low iron without anaemia carries a low cancer risk.
How a GP looks for the cause
- 1
Blood count
A full blood count. No need to prepare.
- 2
Simple checks
A urine test and a coeliac blood test.
- 3
Poo test
If the cause isn’t clear, a FIT test checks your poo for hidden blood.
- 4
Camera tests
Usually first for men and women past the menopause with new anaemia.
Sources: NHS; BSG guideline; NICE NG12
Got iron deficiency anaemia? UK gut doctors say iron treatment shouldn’t wait for these tests, unless a bowel camera test is due very soon.
Still having periods? Gut camera tests aren’t usually needed after the coeliac check. Exceptions include being over 50, gut symptoms, severe or repeated anaemia, or bowel cancer in the family.
Can low iron cause depression?
It’s linked, but not proven to cause it. In a large Taiwan study, adults with iron deficiency anaemia were more likely to get depression and anxiety. Those treated with iron had a lower risk of mental health conditions.
The common signs of low iron are tiredness and lack of energy, shortness of breath, noticeable heartbeats, paler skin and headaches.
Low mood and tired all the time? Tell your GP about both.
There may be other reasons you lack energy, so check with your GP before taking iron. More in always tired.
How can I raise low iron levels?
Find the cause, then top up. Once your GP knows the reason, they’ll recommend treatment.
Six ways to raise low iron
- Tired but not diagnosed? Talk to your doctor or pharmacist before you take iron tablets.
- Eat more meat, pulses, dried fruit, dark-green leafy vegetables and fortified cereals.
- Eat foods with vitamin C at the same time as iron from plants.
- Skip tea or coffee during or after main meals.
- If you’re given iron tablets, take them for as long as advised, usually about 6 months, even with side effects.
- Keep iron supplements to 17mg a day or less, unless a GP advises more, and out of children’s reach.
Sources: NHS; NHS iron; NHS vegan diet; NHS ferrous sulfate
Most people on iron tablets feel better after 3 to 4 weeks. They may take 2 to 4 months to work fully.
Food helps, but slowly. See raising iron with food and when iron tablets aren’t working.
When to speak to a GP
Book an appointment if:
- You think you might have iron deficiency anaemia, such as feeling tired, short of breath or paler than usual.
- You’re a man or past the menopause and a test shows low iron. Ask what is causing it.
- Heavy periods are affecting your life or causing severe pain, or you bleed between periods or after sex.
- You feel tired but haven’t been diagnosed, before you start iron tablets.
Call 111 now if you or your child takes more than the recommended dose of iron tablets.
See also our ferritin blood test guide and iron deficiency blood test.