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What’s the difference between ferritin and iron?

Ferritin is a complex protein that stores iron in an inactive form. So how does it help to identify low iron levels?

Have you recently had a blood test to investigate symptoms of low iron? If so (and depending on which test you had), you may have noticed that a biomarker called ferritin was included. But what is ferritin, and why is it useful when looking at iron? 

Iron is a vital element that we require for several different bodily processes, including: 

  • Creating new red blood cells 
  • Carrying oxygen around the body  
  • Strengthening our immune system 

Most of the iron in our bodies is in haemoglobin, a protein in our red blood cells. A smaller proportion (about 25%) is stored as ferritin, which is found in cells and circulates in the blood [1]. And it’s ferritin that’s responsible for controlling the release of iron when levels are too low or high.  

How much iron do we store? 

The average adult male has about 1,000 mg of stored iron (enough for about three years), whereas women have only about 300 mg (enough for about six months). When iron intake is chronically low, stores can become depleted, decreasing haemoglobin levels. 

Interestingly, it is the ferritin levels that deplete first (rather than iron levels). That’s why ferritin is a good indicator of early anaemia, which may not be apparent from iron levels alone (at first).  

What is ferritin? 

Ferritin is a complex globular protein that stores iron in an inactive form. It is found in many body cells, especially in the liver, spleen, bone marrow, and reticuloendothelial cells [2].  

It plays a significant role in the absorption, storage, and release of iron. As your iron stores deplete, the ferritin releases its iron for use. If your ferritin depletes, you will run out of iron and your ability to produce red blood cells in your bone marrow decreases.  

What is a Ferritin Blood Test? 

A Ferritin Blood Test measures the amount of ferritin in your blood. Because ferritin stores iron, it gives an estimate of your body's iron levels and is a useful tool for detecting iron deficiency. 

What are normal ferritin levels? 

Normal ferritin levels will vary according to your age and sex. Reference ranges will also vary according to the laboratory testing your blood sample.  

NICE defines a ferritin result under30 μg/L as iron deficient. However, it’s possible to have a normal ferritin result and still be iron deficient —ferritin levels increase when there is inflammation in the body which can mask a low result. A full iron panel (Iron Blood Test) can give more insight in these cases. 

Before menopause, women have lower ferritin levels because of losing iron through menstruation. And women who are pregnant may be at risk of iron deficiency or low levels due to the increased requirement for iron within the body. After menopause, average iron levels increase. Our recent ferritin data found just under 5% of women over 60 are iron deficient compared with around 20% of women aged 18-50.  

Generally, ferritin that’s more than 200 μg/L in premenopausal women or greater than 300 μg/L in postmenopausal are considered to be raised. In men, a ferritin result greater than 400 μg/L is usually considered high. 

What do low ferritin levels mean? 

Low ferritin levels could indicate anaemia caused by excessive or chronic bleeding, poor absorption of iron, or too little iron in the diet. 

Ferritin is useful at indicating early anaemia as your iron levels may still be within the normal range, but ferritin levels aren’t. That’s because your body will deplete the iron stores first while iron levels remain sufficient in the meantime.  

Around 20% of menstruating women have low iron levels, which NICE describes as under 30 μg/L in most people. If your ferritin levels are low, additional tests including an iron test, TIBC, and transferrin test are used to confirm a diagnosis of iron deficiency anaemia. 

Symptoms of low ferritin levels include: 

  • Pale skin 
  • Fatigue 
  • Dizziness 
  • Heart palpitations 
  • Shortness of breath 

What do high ferritin levels mean? 

As ferritin is an acute phase protein, it can increase during infection, inflammation, or trauma.  

High ferritin levels can occur with: 

  • An infection of some kind 
  • Inflammation (such as rheumatoid arthritis) 
  • Heavy alcohol use 
  • Overuse of ferritin supplements 
  • Overactive thyroid 
  • Liver disease 
  • Kidney failure 
  • Haemochromatosis (iron overload syndrome) is an inherited condition where the body cannot rid itself of iron - so it accumulates over time 
  • Some types of cancers 

High ferritin levels are often (but not always) associated with iron overload. If iron levels continue to increase, it can accumulate in the liver and other organs causing damage. 

How can I increase my ferritin levels? 

Generally (unless our doctor advises you otherwise), low ferritin levels can be improved by changes to your diet.  

Ways to increase ferritin levels:  

  • Increase your intake of red meat, dark green leafy vegetables (like spinach and kale), fortified cereals and bread, and pulses (beans, peas and lentils).  
  • Eat iron-rich foods alongside a good source of vitamin C (such as orange or lemon juice) to help improve your absorption of iron.  
  • Iron supplements are also widely available, and you can talk to your pharmacist about which one is right for you.  

How can I reduce my ferritin levels? 

In many cases, raised ferritin levels are temporary due to inflammation or infection. Your ferritin levels are likely to settle as you feel better.  

If our doctors suspect iron overload, they’ll advise you to see your doctor. Otherwise, you may be able to reduce the iron in your blood through diet. 

Ways to decrease ferritin levels:  

  • Reduce your intake of iron-rich foods such as red meat. 
  • Avoid using iron cookware. 
  • Don’t consume vitamin C with foods that are rich in iron.  
  • If you are supplementing with iron, reduce your dose after consulting your doctor as high levels of iron can be damaging.  

Another surprising way to reduce iron levels is to donate blood regularly, as this gets rid of excess iron in the body. 

So, what is iron? 

Iron is a vital component of three fundamental processes of life, including: 

  • Oxygen transport 
  • DNA synthesis 
  • Oxidative phosphorylation  

About half of the body’s iron (about 2.1g) is in red blood cells in the oxygen-transporting haemoglobin. About another gram is in macrophages (white blood cells) and the oxygen-transporting myoglobin of muscles. Excess iron is stored in the liver. 

Iron deficiency is the most common cause of anaemia worldwide [3]. If you are low in iron, your body will struggle to get enough oxygen to the tissues — this can make you feel more fatigued and cause you to get tired quicker.  

Where do you get iron from? 

You get your iron from two main sources: 

  1. Your diet (about 5%)  
  2. The breakdown and turnover of your red blood cells (about 95%) 

In your diet, there are two main types of iron: Fe2+, which is found in meat and dairy products, and Fe3+, which is harder to absorb and found in plant-based foods. 

Symptoms of low iron (or iron deficiency anaemia) 

Symptoms of iron deficiency anaemia can include: 

  • Tiredness and lack of energy 
  • Shortness of breath 
  • Noticeable heartbeats (heart palpitations) 
  • Pale skin 

If you’re experiencing symptoms of iron deficiency, a simple blood test can check your iron-related biomarkers.  

What is an Iron Blood Test? 

Our Iron Blood Test looks at several measures of iron (not just iron or ferritin). Together, these markers evaluate how much iron you have in your blood, to diagnose low iron levels or monitor existing iron deficiency. 

Importantly, our Iron Blood Test also includes an inflammation marker (CRP-hs) to help distinguish causes of raised ferritin. 

What are normal iron levels? 

Serum iron is a very transient reading and can be influenced by the amount of iron-rich food in your diet in the days before your blood test. For this reason, it’s rare for iron to be looked at on its own. At Medichecks, we interpret iron alongside other markers to get a whole picture of iron health. 

Again, a normal range will depend on the laboratory that’s interpreting your results. However, we show all results within the normal, borderline, and out-of-range scale so you’ll be able to see where you sit for each biomarker and what this may mean for you.  

What do low iron levels mean? 

If your results are low, it’s important to look at this in the context of other iron markers, particularly ferritin.  

Low iron could mean:  

  • You haven’t eaten much iron recently (or in general for your body’s needs) 
  • Your body can't absorb iron properly because you have a gut or bowel condition like coeliac disease or Crohn's 
  • You’ve lost blood through menstruation or internal bleeding, often in the digestive tract 
  • You need further investigation for iron deficiency anaemia (which can also develop in pregnancy) 

What do high iron levels mean? 

Raised iron in the blood can indicate iron overload syndrome (haemochromatosis) an inherited condition where your body cannot rid itself of excess iron. This would usually be accompanied by elevated ferritin and transferrin saturation levels.  

A high result could also mean you’re overdoing it on the iron supplements, or you’ve recently eaten an iron-rich meal. Taking all biomarkers and your lifestyle into consideration is so important when it comes to analysing results.  

For more on this, have a look at our blog: what is iron overload?  

Finally, is ferritin the same as iron? 

If you had ever wondered whether ferritin and iron are one of the same, you certainly wouldn’t have been alone.  

The main difference is that iron is a mineral (present in red blood cells that carries oxygen) whereas ferritin is a protein that stores iron and releases it when the body needs it. So, even though they aren’t the same, they certainly work together.


 References 

  1. ucsfhealth.org. 2022. Hemoglobin and Functions of Iron. [online] Available at: <https://www.ucsfhealth.org/education/hemoglobin-and-functions-of-iron> [Accessed 14 July 2022]. 
  2. South Tees Hospitals NHS Foundation Trust. 2022. Ferritin - South Tees Hospitals NHS Foundation Trust. [online] Available at: <https://www.southtees.nhs.uk/services/pathology/tests/ferritin/> [Accessed 14 July 2022]. 
  3. Miller, J., 2022. Iron Deficiency Anemia: A Common and Curable Disease
  4. Cks.nice.org.uk. 2022. Investigations | Diagnosis | Anaemia - iron deficiency | CKS | NICE. [online] Available at: <https://cks.nice.org.uk/topics/anaemia-iron-deficiency/diagnosis/investigations/> [Accessed 14 July 2022].