Ferritin is one of those results people remember. "My ferritin was low" is a common phrase among people with heavy periods, people who exercise a lot and anyone who has been through a spell of tiredness. Less well known is that ferritin can also be high, and that a high result does not always mean too much iron. A ferritin blood test is simple, but reading it well takes a little context.
What ferritin is
LML describes ferritin as a protein that stores iron in the body. Because the amount in the blood broadly follows the size of the body's iron reserves, it is the most widely used single marker of iron stores. British guidance on iron deficiency anaemia in adults treats a low ferritin as a strong sign of low iron stores (Snook et al., 2021).
There is an important catch. Ferritin is also what is called an acute phase protein: it rises when there is inflammation in the body. LML notes that inflammation for any reason, such as autoimmune conditions, infections or excessive alcohol, can push ferritin up, sometimes a lot. That means a normal or even high ferritin does not always rule out low iron when inflammation is present (Namaste et al., 2017).
When ferritin is low
A low ferritin usually points to low iron stores. Iron deficiency is one of the most common nutritional problems in the world and can exist before anaemia appears (Pasricha et al., 2021). Common reasons include:
- blood loss, including heavy periods;
- pregnancy, when iron needs rise;
- diets low in iron;
- conditions that affect absorption from the gut.
LML notes that in women, low ferritin is often linked to menstruation or pregnancy. In adults, British guidance recommends that the cause of iron deficiency is looked into by a doctor rather than simply treated (Snook et al., 2021).
When ferritin is high
A high ferritin is common, and most of the time it is not caused by iron overload. A British guideline on investigating a raised ferritin lists frequent causes such as inflammation, liver disease, regular alcohol intake and features of metabolic syndrome, and explains that transferrin saturation helps separate these from true iron overload (Cullis et al., 2018).
When ferritin and transferrin saturation are both raised, a doctor may consider haemochromatosis, an inherited condition in which the body absorbs too much iron. LML notes that in men, high ferritin may be associated with haemochromatosis or liver disease. We cover iron overload and the HFE gene test in a separate guide.
Why ferritin is better read with the rest of the iron profile
On its own, ferritin can mislead in either direction. The Iron Status Profile in the BPR catalogue adds the other measures that make the picture clearer. LML describes them like this:
- Serum iron: how much iron is in the blood right now. Because it reflects the moment of the sample, it is rarely read alone.
- Total iron-binding capacity (TIBC) and unsaturated iron-binding capacity: how much iron the blood's transport protein could carry.
- Transferrin saturation: how much of that capacity is actually in use, another way of seeing how well the body is using its iron.
- Ferritin: the store.
If inflammation might be affecting the result, a professional may also look at an inflammation marker such as C-Reactive Protein (High Sensitivity), which is in the catalogue too. Research on adjusting ferritin for inflammation shows how much this can change the interpretation (Namaste et al., 2017).
Ferritin on its own or the full profile?
- Ferritin alone can be enough for a simple follow-up, for example after a course of iron that a doctor prescribed.
- The Iron Status Profile is more useful for a first look, or when the ferritin result is borderline or high.
- If you also want haemoglobin and blood cell counts, the Anaemia Profile, covered in another guide, combines both.
