What Is Non-Anaemic Iron Deficiency (NAID)?
Non-anaemic iron deficiency (NAID) — sometimes called iron deficiency without anaemia — is a condition in which the body's iron stores are depleted, as shown by a low ferritin, but haemoglobin remains within the normal reference range.
This is a critically important distinction. The conventional medical definition of "anaemia" requires haemoglobin to fall below a threshold (approximately 12.0 g/dL in women, 13.0 g/dL in men). Many patients — and unfortunately some clinicians — assume that if haemoglobin is normal, there is no iron problem. This is incorrect.
Key fact: Ferritin is the protein that stores iron in the body. A low ferritin — regardless of haemoglobin — means your body's reserves are depleted. This can cause significant symptoms even when Hb is "normal." Most clinical guidelines define iron deficiency as ferritin below 30 µg/L, irrespective of Hb.
Why Does Haemoglobin Stay Normal When Ferritin Is Low?
The body has a carefully designed iron hierarchy. It uses available iron to serve its most critical functions first — and maintaining haemoglobin to carry oxygen to vital organs is at the top of the list. Hair follicles, energy metabolism, and cognitive function are lower priorities.
As iron stores deplete, the body draws them down to maintain Hb production. Haemoglobin can therefore remain in the normal range for months while ferritin falls progressively lower. By the time Hb drops — triggering the formal diagnosis of anaemia — ferritin has often been critically low for a long time. In this sense, a normal haemoglobin with low ferritin is not reassuring: it simply means the body is still compensating.
Symptoms of Non-Anaemic Iron Deficiency
NAID produces a recognisable symptom cluster. Because these symptoms develop gradually and haemoglobin remains normal, they are often attributed to stress, poor sleep, or depression rather than iron deficiency:
Cognitive & Energy
- Persistent fatigue despite adequate sleep
- Brain fog and poor concentration
- Low mood and motivation
- Reduced exercise tolerance
- Feeling cold all the time
Physical Signs
- Hair thinning and increased shedding
- Brittle nails
- Restless legs at night
- Breathlessness on exertion
- Headaches
If these symptoms resonate, and your ferritin is below 30 µg/L, the connection is likely to be real — regardless of what your haemoglobin shows.
Why NAID Goes Untreated So Often
There are several reasons patients with NAID spend years without appropriate treatment:
- NHS screening focuses on Hb: Routine blood count panels flag anaemia but may not prominently flag low ferritin with normal Hb.
- Reference ranges are conservative: Many labs only flag ferritin as abnormal when it falls very low (below 10–12 µg/L), despite guidelines supporting treatment at below 30 µg/L.
- GPs vary in approach: Without a formal anaemia diagnosis, some GPs may not feel confident prescribing iron — particularly if their lab reports ferritin as "within range."
- Symptoms are non-specific: Fatigue, brain fog, and hair loss are common presenting complaints with many possible causes, so the connection to iron is not always investigated.
Treatment Options for NAID
Both oral iron and IV iron infusion can correct non-anaemic iron deficiency. The choice depends on the severity of your ferritin depletion, your symptoms, and your ability to tolerate oral iron.
For patients with ferritin between 15–30 µg/L with mild symptoms, a trial of oral iron is reasonable. For those with ferritin below 15 µg/L, significant symptoms, prior tablet intolerance, or gut conditions affecting absorption, an IV iron infusion is often the more efficient and reliable option — restoring ferritin in weeks rather than months.
Book an Iron Assessment
If your ferritin is low and you are symptomatic — regardless of what your haemoglobin shows — book an iron assessment at Lambert Medical Practice. Our GP will assess your full iron panel, calculate your iron requirement, and recommend the most appropriate treatment.