Iron and Ferritin Test: Symptoms of Deficiency and Reading Results

Feeling constantly tired, breathless, or noticing unusual hair loss, but being told your initial blood tests are 'normal'? You are not alone, and the answer might lie in a deeper understanding of your iron levels.

As GPs, we frequently speak to patients struggling with unexplained fatigue. Iron is vital for energy and overall health, but standard blood tests can sometimes tell only half the story. To get a good picture, doctors need to look at ferritin. Ferritin is a measure of your body's iron stores, which tells a very different story to the iron currently circulating in your blood.

This guide is for anyone who is experiencing symptoms of iron deficiency or overload, has been advised to have an iron or ferritin test, or wants to make sense of their test results.

In this article, we will cover the key symptoms to watch for and explain the difference between ferritin and other iron tests. We will also help you understand what your results really mean (even the confusing ones), and outline the next steps you can take to support your health.

What are iron and ferritin?

Iron is an essential mineral that your body uses to produce haemoglobin, enabling red blood cells to carry oxygen efficiently. Ferritin is the specific protein that stores this iron inside your cells for future use. Together, testing both provides a good picture of your immediate iron supply and long-term reserves.

The role of iron

Iron is a crucial mineral required to make haemoglobin. Haemoglobin is a protein found in red blood cells that carries oxygen from your lungs to the rest of your body, as explained by the NHS. Without enough iron, your body cannot produce enough healthy red blood cells. This lack of oxygen transport can affect your energy production, and immune function

What is ferritin?

Ferritin is a protein that stores iron inside your cells and releases it in a controlled way. A ferritin blood test measures the amount of stored iron in your body, providing a estimate at your iron reserves. Think of your body's iron like money: ferritin is the savings in your bank account, while serum iron is the loose cash currently in your wallet.

Ferritin vs serum iron

Serum iron measures the amount of iron currently circulating in your blood. This level can fluctuate daily depending on what you have recently eaten or the time of day. Ferritin measures your long-term iron stores, making it a much more reliable indicator of your overall iron status. To evaluate your iron health fully, doctors often look at Total Iron-Binding Capacity (TIBC) alongside these markers.

Symptoms of low and high iron levels

Low iron levels typically cause tiredness, breathlessness, and pale skin, whereas high iron levels can lead to joint pain and chronic fatigue over time.

Symptoms of iron deficiency

When your iron stores run low, your body struggles to produce enough haemoglobin to transport oxygen effectively. This lack of oxygen causes the classic signs of iron deficiency. According to the NHS, the most common symptoms include unexplained fatigue or tiredness, shortness of breath, noticeably pale skin, and heart palpitations (noticeable heartbeats).

Lesser-known deficiency symptoms

Beyond tiredness, iron deficiency can cause several less obvious symptoms that people often do not connect to their iron levels. These include unusual hair loss, brittle or spoon-shaped nails, restless leg syndrome, and cracks at the corners of the mouth (angular cheilitis). Some people also experience pica, which is an unusual craving to eat non-food items like ice or dirt. If you are struggling with low energy, you might find our guide on understanding fatigue helpful.

Symptoms of iron overload

Having too much iron can also cause significant health issues. Iron overload (such as in the condition haemochromatosis) causes iron to build up in the body's organs. Symptoms of high iron are often non-specific and develop slowly over a long period. They can include chronic fatigue, joint pain, abdominal pain, loss of libido, and heart problems.

If you are low iron and have new symptoms and feel unwell;; e.g. fainting, dizziness, chest pain, new tar like stool, then attend A+E.

How iron status is tested

Your iron status is tested using a blood test called an iron studies panel, which measures your ferritin, serum iron, and the proteins that transport iron around your body.

Reasons for an iron panel

A GP will often order an iron panel to investigate symptoms of anaemia or iron overload. This is too look for the causes, possible diagnoses include fibroids, bowel cancer and gut problems.

We also use these tests to screen for iron deficiency in at-risk groups, such as pregnant women or people with gastrointestinal conditions. As noted in NICE guidance, blood tests including iron indices are important for assessing conditions like gastrointestinal bleeding, which is a very common cause of iron deficiency.

The full iron panel

To get the context of your iron health, doctors look at a full 'iron studies' panel. As outlined by the NHS, this includes:

Result patterns for conditions

Looking at these markers together helps your doctor diagnose the specific issue.

In the table you can see some possible results but usually this needs interpreting along with your medical history, medication and symptoms.

Reading ferritin and iron test results

Reading your results involves comparing your ferritin and transferrin saturation levels against laboratory reference ranges to see if your iron stores are depleted, optimal, or overloaded.

Normal reference ranges

Normal reference ranges for ferritin are measured in micrograms per litre (µg/L) and can vary slightly between different laboratories and countries. Keep in mind that a 'normal' laboratory result is not always the same as an 'optimal' level for your personal health, which is why your results should always be discussed with a clinician.

Low ferritin levels

A low ferritin level is one of the earliest and most sensitive indicators of iron deficiency. It means your body's iron stores are depleted. This drop in storage happens before your serum iron falls or anaemia develops. This is usually under 30 µg/L.
Common causes include inadequate dietary intake, poor absorption (such as in coeliac disease), or blood loss. For example, NICE guidance highlights heavy menstrual bleeding as a primary cause of iron deficiency that must be identified and treated.

High ferritin levels

A high ferritin result may indicate iron overload, where the body absorbs too much iron. However, ferritin is also what doctors call an 'acute-phase reactant'. This means ferritin levels can spike due to inflammation, infection, liver disease, or certain cancers, even if your actual iron stores are normal or low. Other causes are alcohol, fatty liver and inflammation.

Misleading normal results

In virtual GP consultations, a frequent source of frustration for patients is feeling terrible despite being told their ferritin is 'normal'. If you have a condition causing inflammation (like an infection, an autoimmune disease, or chronic kidney disease), your ferritin can appear 'falsely normal' or high. This can hide an underlying iron deficiency.

To clarify this 'grey zone', doctors evaluate your transferrin saturation alongside markers of inflammation. According to clinical guidelines from the Royal United Hospitals Bath NHS Foundation Trust, a transferrin saturation of less than 20% can help support a diagnosis of iron deficiency

Next steps after your results

Based on your results, a clinician will determine if you have non-anaemic iron deficiency or iron deficiency anaemia, and will recommend dietary changes, supplements, or further investigation.

Non-anaemic iron deficiency

You can have low iron without being anaemic. Non-Anaemic Iron Deficiency (NAID) occurs when your iron stores (ferritin) are low enough to cause symptoms like fatigue and hair loss, but your haemoglobin level is still within the normal range. Identifying and treating NAID can help improveyour symptoms and prevent the condition from progressing to full anaemia.

Iron deficiency anaemia

Iron Deficiency Anaemia (IDA) happens when your low iron stores have led to insufficient haemoglobin production. This results in fewer, smaller red blood cells that cannot carry enough oxygen around your body. According to NICE CKS guidance, this requires medical treatment to replenish iron stores and correct the anaemia.

Increasing iron levels

• Diet: Eating iron-rich foods can help maintain levels. This includes haem iron from meat and fish, and non-haem iron from plants like lentils, spinach, and tofu. Pairing non-haem iron with Vitamin C can help improve absorption.
• Supplements: If you have a diagnosed deficiency, dietary changes alone are rarely enough, and iron supplements are often necessary. Common forms include ferrous fumarate and ferrous sulphate. There are some medications and food that can affect absorption so remember to check - this can include coffee. Side effects like constipation can occur, so a doctor can help you find a suitable type and dose. Due to the risks of iron overload, you should only take high-dose iron supplements under medical advice. Also worth noting supplements can make your poo darker or black.
• Further investigation: A doctor will investigate the underlying cause of your deficiency, rather than just treating the low number on your blood test.Finding the underlying cause of iron deficiency is important to rule out serious causes and make sure the treatment is accurate. Causes can include gastrointestinal bleeding, coeliac disease or, less commonly, bowel cancer. 

Preparing for your doctor's appointment

To get the most out of your appointment, prepare a complete list of your symptoms, medical history, and specific questions about your iron panel results.

Information to share

Before speaking to a GP, make a list of all your symptoms, even the strange ones like unusual cravings or restless legs. Note any relevant medical history, such as gut issues or heavy periods. Finally, list your typical daily diet and note down any supplements you are currently taking.

Questions to ask

Consider taking a checklist of questions into your consultation:

• Given my symptoms, what do you consider an optimal ferritin level for me?
• Could my results indicate non-anaemic iron deficiency?
• Do we need to consider inflammation affecting my ferritin level?
• What is the best type of iron supplement for me to take, and at what dose?
• What follow-up tests will I need to monitor my levels?

For more advice on getting the right support, read our guide on how to make the most of your GP appointment.

Conclusion

Ferritin is a measure of your body's iron stores and is a much more sensitive marker than serum iron alone. Symptoms of iron deficiency can appear long before you develop full anaemia, a state known as non-anaemic iron deficiency. Keep in mind that a 'normal' ferritin result can also be misleading if you have underlying inflammation masking a deficiency.

Understanding your full iron panel is the first step towards addressing your symptoms and improving your health. Do not dismiss persistent symptoms even if you have been told your initial results are in the normal range. If you are concerned about your symptoms, need help interpreting your test results, or want to discuss treatment options, book an appointment with a Doctor Care Anywhere GP today.