Ferritin

Ferritin is a protein that stores iron inside your cells, and the amount of ferritin in your blood is the most reliable indicator of your body's total iron reserves. Think of ferritin as a storage cupboard for iron: when your body has plenty of iron coming in from food, it tucks the surplus away inside ferritin molecules for later use; when supplies run low, it opens the cupboard and releases iron back into circulation. Measuring your ferritin level matters because it can reveal iron depletion at an early stage, often well before it shows up in your haemoglobin or red blood cell count. Healthy iron stores are essential for producing the red blood cells that carry oxygen around your body, for sustaining your energy levels, and for supporting your immune system.

Your body needs iron for a remarkable number of tasks. It is the central atom in haemoglobin, the molecule inside red blood cells that picks up oxygen in the lungs and delivers it to every tissue and organ. Iron also plays a role in muscle function through a related protein called myoglobin, and it helps enzymes involved in energy production do their work. When ferritin levels drop too low, your body starts to ration its remaining iron, and you may notice symptoms such as tiredness, breathlessness during exercise, or feeling the cold more than usual. On the other hand, ferritin can sometimes rise for reasons unrelated to iron, it is also what is known as an acute phase reactant, meaning it can increase during periods of inflammation or infection.

A variety of factors influence your ferritin level. Dietary iron intake is the most obvious one: red meat, liver, and shellfish provide highly absorbable iron, while plant sources such as lentils, spinach, and fortified cereals offer a form that is absorbed less efficiently. Menstruation, pregnancy, and regular intense exercise can all increase iron demand and gradually draw down stores. Conditions affecting the gut, such as coeliac sensitivity, may reduce absorption. Vitamin C helps your body absorb iron from food, so pairing iron-rich meals with fruit or vegetables is a simple, practical strategy. If your ferritin is higher or lower than expected, your GP can investigate the cause and recommend the most appropriate course of action for you.