Iron deficiency is among the most common nutritional deficiencies worldwide and one of the most frequently missed diagnoses. Symptoms — fatigue, brain fog, cold intolerance, breathlessness — overlap with dozens of other conditions, and a routine full blood count can look normal even when iron stores are depleted. A full iron studies panel is the only way to see the complete picture.
Why a full blood count isn't enough
Anaemia — a low haemoglobin or haematocrit — is the late-stage consequence of iron deficiency, not the early one. By the time haemoglobin falls, iron stores have usually been low for months. An iron studies panel catches the problem earlier, before anaemia develops.
Serum iron
Serum iron measures the amount of iron currently circulating in your blood. It's highly variable — it changes with time of day (highest in the morning), recent meals, and acute illness. A single low serum iron reading is a hint, not a conclusion. It's always interpreted alongside the other markers.
Normal range: roughly 60–170 micrograms per decilitre (mcg/dL), though reference ranges vary by laboratory.
Ferritin
Ferritin is the storage form of iron — the body's reserve tank. It's the single most useful marker for detecting iron deficiency before anaemia sets in. A low ferritin almost always means iron stores are depleted.
The important caveat: ferritin is also an acute-phase reactant. During inflammation, infection or chronic disease, ferritin can rise — sometimes dramatically — even when actual iron stores are low. This is why a 'normal' or high ferritin doesn't always rule out functional iron deficiency, particularly in people with inflammatory conditions.
Normal range: approximately 20–200 ng/mL for women, 20–300 ng/mL for men. Many haematologists consider levels below 30–50 ng/mL worth treating when symptoms are present.
TIBC (Total Iron-Binding Capacity)
TIBC measures how much iron your blood could carry if all your transport proteins (mainly transferrin) were saturated. When iron stores are low, the body produces more transferrin to capture every available iron molecule — so TIBC goes up. A high TIBC alongside low ferritin and low serum iron is the classic iron deficiency pattern.
Normal range: approximately 250–370 mcg/dL.
Transferrin saturation
Transferrin saturation (TSAT) is calculated from serum iron and TIBC: it tells you what percentage of your transport capacity is actually carrying iron. Below 20 percent suggests deficiency; below 15 percent is consistent with iron-deficiency anaemia. Very high saturation (above 45–50 percent) can indicate iron overload — a different problem requiring different investigation.
Reading the pattern
No single value tells the whole story. Doctors look for the pattern:
- Iron deficiency: low ferritin, low serum iron, high TIBC, low transferrin saturation
- Anaemia of chronic disease: normal or high ferritin, low serum iron, normal or low TIBC
- Iron overload (haemochromatosis): high ferritin, high serum iron, high transferrin saturation
What to do with your results
If your iron studies suggest deficiency, treatment depends on severity and cause. Mild deficiency in otherwise healthy people is often managed with dietary changes and oral iron supplements. More severe deficiency, or deficiency caused by poor absorption, may require intravenous iron. Identifying and treating the underlying cause — bleeding, absorption issues, dietary insufficiency — is always part of the plan.
Keep your iron study results together over time. The trend — are stores improving with treatment? — matters as much as any single reading.