What Blood Tests Show Iron Deficiency?

If you’re feeling persistently tired, foggy, short of breath, or struggling to keep up with daily activities, iron deficiency may be contributing. Blood tests called iron studies help assess your iron levels – however iron deficiency is not identified by a single number.

To understand whether your body has enough iron, we look at a group of blood test results (called iron studies or anaemia studies) that together show how iron is stored, transported, and used.

Typically, iron studies incorporate

• Ferritin: Shows how much iron your body has stored and is the most important test for diagnosing iron deficiency. Ideally, this should be above 50mcg/L (which is different from many laboratory reference ranges). This is the primary parameter we look at.

• Transferrin Saturation (%): Indicates how much iron is being delivered to your body’s tissues. Less than 20% often reflects iron deficiency even with a normal ferritin.

• Total Iron Binding Capacity (TIBC): Reflects how hard your body is working to transport iron in the bloodstream.

• Serum Iron: Measures the very small amount of iron circulating in your blood at the time of the test and can vary from day to day. This is the least useful indicator of your body’s iron status.

• Haemoglobin (Hb): Measures your blood’s ability to carry oxygen and is often normal in non-severe iron deficiency.

Iron deficiency and anaemia are not the same condition, and ferritin cut-offs do not always tell the full story. While current guidelines often define iron deficiency as a ferritin below 30 micrograms per litre, ferritin is influenced by many factors including inflammation, chronic illness, liver disease, obesity, infection, and metabolic stress. This means some people can have “normal” or even elevated ferritin levels while still having clinically significant iron deficiency.

In this video, Dr Joel Collins, Clinical Haematologist and Practice Principal of The Iron Infusion Clinic, explains why ferritin must always be interpreted in the context of symptoms, overall health, and other blood test results – not as a standalone number. Many patients with ongoing fatigue, brain fog, reduced exercise tolerance, hair loss, restless legs, or poor concentration may still be iron deficient despite being told their iron studies are “normal”.

The discussion also explores why many people with ferritin levels over 50mcg/L – and sometimes even over 100–200 mcg/L may benefit from specialist led clinic assessment for iron deficiency.

Ferritin (Iron Stores)

Ferritin is the most important marker when assessing iron deficiency. It reflects how much iron your body has stored.

• A low ferritin level confirms iron deficiency, even if other blood tests are normal.

• Standard laboratory reference ranges may underestimate iron deficiency.

• Many people with a ferritin below 50 micrograms/L have symptoms consistent with iron deficiency, despite being told their results are “normal”.

Transferrin Saturation (%)

This test shows how much of your transferrin (the protein that carries iron) is actually bound to iron.

• Low transferrin saturation suggests that insufficient iron is being delivered to tissues and organs.

• This can contribute to fatigue, brain fog, and reduced physical performance.

Total Iron Binding Capacity (TIBC)

These markers indicate how strongly your body is trying to bind and transport iron.

• High transferrin or TIBC levels often mean the body is “seeking” more iron, which is common in iron deficiency.

Serum Iron

Serum iron measures the amount of iron circulating in the blood at the time of testing.

• Levels can fluctuate significantly from day to day.

• On its own, serum iron does not reflect iron stores and should never be used in isolation.

Haemoglobin (Hb)

Haemoglobin measures the blood’s capacity to carry oxygen.

• Low haemoglobin indicates anaemia.

• However, haemoglobin is often normal in early or moderate iron deficiency, meaning iron deficiency can be missed if ferritin is not checked.

You can be iron deficient without being anaemic. We call this non-anaemic iron deficiency (NAID). This is a common situation in Australia, and causes a significant burden of symptoms that lower quality of life.

If you’re unsure whether your blood tests are complete, or you’re experiencing symptoms despite being told your results are normal, our team can help review your iron studies and guide you on the appropriate next steps.

Our iron deficiency screening tool can be found here Iron Deficiency Screening Tool

Iron deficiency and anaemia are commonly confused, but they are not the same condition.

Anaemia specifically refers to a low haemoglobin level (Hb), meaning the blood has a reduced capacity to carry oxygen. Iron deficiency is one of the most common causes of anaemia, but importantly, a person can be iron deficient without being anaemic.

In this video, Dr Joel Collins – Clinical Haematologist and Practice Principal of The Iron Infusion Clinic explains the important differences between iron deficiency and anaemia, and why iron deficiency can still cause significant symptoms even when standard blood counts appear “normal”.

Iron plays a critical role in far more than just red blood cell production. It is also essential for muscle function, neurological development, neurotransmitter activity, cognition, energy production, and overall wellbeing. This is why many patients with low iron stores experience symptoms such as fatigue, brain fog, poor concentration, exercise intolerance, restless legs, headaches, or reduced quality of life long before anaemia develops.