Understanding iron levels, symptoms, testing and treatment options including iron infusion

Why Iron Levels Matter for Energy, Health and Performance 

Iron deficiency occurs when the body does not have sufficient iron to meet its needs. It is the most common nutritional deficiency worldwide and affects people of all ages. 

Iron is essential for producing haemoglobin, the protein in red blood cells that carries oxygen around the body. 

Iron deficiency often develops gradually. In the early stages, iron stores become depleted while haemoglobin levels may remain within the normal range. Over time, as levels fall further, the body produces fewer healthy red blood cells and iron deficiency anaemia (IDA) develops. 

Because this process can occur slowly, many people live with symptoms for months, sometimes years, before the underlying cause is recognised. 

Understanding Ferritin 

Iron status is usually assessed with a blood test called ferritin, which reflects the body’s stored iron. 

Laboratory reference ranges for ferritin can be quite wide. This means a result may technically fall within the “normal” range but still be relatively low for optimal physiological functioning, particularly in women. 

It is therefore possible to experience symptoms of iron deficiency even when haemoglobin levels remain normal and ferritin sits at the lower end of the reference range. This is sometimes referred to as iron deficiency without anaemia. 

For this reason, iron results should always be interpreted in the context of symptoms, medical history and overall health, rather than relying on laboratory numbers alone. 

Symptoms of Iron Deficiency 

Iron deficiency can affect both physical and cognitive wellbeing, and symptoms often develop gradually. 

Common symptoms include: 

• Persistent fatigue or low energy 

• Brain fog or difficulty concentrating 

• Reduced exercise tolerance 

• Shortness of breath, particularly with exertion 

• Palpitations 

• Headaches 

• Hair thinning or hair loss 

• Pale skin 

• Dry mouth or brittle nails 

• Poor sleep 

• Some people may also experience restless legs or low mood, and many patients simply describe feeling constantly exhausted despite adequate sleep or struggling to maintain their usual level of activity. 

Untreated iron deficiency can significantly affect quality of life, daily functioning and overall wellbeing. 

When to Check Your Iron Levels 

Iron deficiency can sometimes be difficult to recognise because symptoms such as fatigue, poor concentration or reduced exercise tolerance are often attributed to busy lifestyles, stress or lack of sleep. 

It may be worth checking your iron levels if you experience persistent fatigue, breathlessness with activity, brain fog, hair thinning or reduced stamina, particularly if these symptoms continue over time. 

Testing may also be helpful for individuals with heavy menstrual bleeding, during or after pregnancy, those following restrictive diets, endurance athletes, or anyone experiencing persistent unexplained fatigue. 

A simple blood test measuring ferritin and haemoglobin levels can help assess iron status and guide appropriate treatment where needed. 

Causes of Iron Deficiency 

Iron deficiency can occur for several reasons, and identifying the underlying cause is an important part of management. 

Common causes include: 

• Heavy menstrual bleeding 

• Pregnancy and the post-partum period 

• Dietary insufficiency 

• Gastrointestinal blood loss 

• Reduced iron absorption, for example in coeliac disease Increased physiological demand, such as in endurance athletes 

• In women, menstrual blood loss remains one of the most frequent causes. In other patients, gastrointestinal or metabolic causes may need to be considered. 

Iron and Physical Performance 

Iron plays an important role in oxygen transport, energy production and muscle function, all of which are essential for physical performance. 

When iron levels are low, the body’s ability to deliver oxygen to working muscles is reduced. This can lead to reduced endurance, slower recovery and increased fatigue during exercise. 

Iron deficiency is not uncommon in individuals who train regularly, particularly endurance athletes such as runners and cyclists. Increased physical demands, dietary factors and small but repeated iron losses during training can all contribute. 

Importantly, iron deficiency can occur even when haemoglobin levels remain normal, meaning ferritin levels may be low while routine blood tests still appear within the normal range. 

For individuals who train frequently or participate in competitive sport, assessing iron status can therefore be an important part of maintaining optimal health, recovery and performance. 

Treatment for Iron Deficiency 

Treatment focuses on restoring iron levels and addressing the underlying cause. 

When iron deficiency is identified and appropriately treated, many patients notice improvements in energy levels, concentration, exercise tolerance and overall wellbeing. 

Management may include: 

• Dietary advice 

• Oral iron supplementation 

• Investigation of contributing medical conditions 

• Intravenous iron infusions 

• Iron tablets are often used first, but some patients find them difficult to tolerate due to gastrointestinal side effects such as nausea or constipation. In other cases, iron may not be well absorbed. 

When this happens, intravenous iron infusion can provide an effective alternative, allowing iron stores to be replenished more efficiently. 

When Is an Iron Infusion Recommended? 

In some situations, iron tablets may not be sufficient to restore iron levels. This may occur when iron is poorly absorbed, when tablets cause significant side effects, or when iron levels need to be corrected more quickly. 

An intravenous iron infusion allows iron to be delivered directly into the bloodstream, bypassing the digestive system. This can replenish iron stores more efficiently and is often well tolerated. 

Iron infusions may be considered in situations such as significant iron deficiency, during pregnancy, in patients with gastrointestinal conditions affecting absorption, or when oral supplements have not been effective. 

A Multidisciplinary Approach 

Iron deficiency can intersect with several areas of health, including women’s health, pregnancy, gastrointestinal health, mental wellbeing and chronic medical conditions. 

At Central Health London, patients benefit from a collaborative, multidisciplinary approach. Where appropriate, care may involve input from our GPs alongside specialist clinicians across areas such as women’s health, obstetrics, mental health and general medicine, ensuring a comprehensive assessment and an individualised treatment plan for both men and women. 

If you would like advice about iron deficiency or treatment options, including iron infusion therapy, our clinical team would be happy to help. 

Frequently Asked Questions 

What ferritin level is considered low? 

Ferritin reference ranges vary between laboratories. However, symptoms of iron deficiency may occur even when ferritin sits within the lower end of the normal reference range. Results should always be interpreted in the context of symptoms and clinical history. 

Can you have iron deficiency without anaemia? 

Yes. Iron stores can become depleted before haemoglobin levels fall. This is known as iron deficiency without anaemia and can still cause symptoms such as fatigue, poor concentration and reduced exercise tolerance. 

How long does it take to recover from iron deficiency? 

Recovery time depends on the underlying cause and treatment used. Oral supplements may take several months to restore iron levels, while intravenous iron infusion can replenish iron stores more quickly. 

When should iron deficiency be investigated further? 

If iron deficiency persists, recurs, or cannot be explained by common causes such as menstrual blood loss or pregnancy, further investigation may be recommended to identify underlying gastrointestinal or metabolic causes.