Iron Deficiency Without Anaemia: A Common But Under-Recognised Condition
Most people associate iron deficiency with anaemia — low haemoglobin (Hb). But a significant proportion of iron-deficient patients have a normal Hb and low ferritin. This is called iron deficiency without anaemia (IDWA), and it's one of the most commonly under-diagnosed conditions in UK primary care.
The reason haemoglobin stays normal while ferritin drops is straightforward: the body prioritises iron for haemoglobin production above all else. When iron intake is insufficient (due to diet, absorption problems, or blood loss), the body draws on ferritin stores to maintain red blood cell production. Hb stays normal. Ferritin falls. By the time Hb starts to drop, ferritin may already be severely depleted.
Key fact: ferritin 15 is clinically significant iron deficiency
Most clinical guidelines define iron deficiency as ferritin below 30 µg/L, regardless of haemoglobin level. A ferritin of 15 µg/L falls well below this threshold. The British Society of Gastroenterology and National Institute for Health and Care Excellence (NICE) both recognise IDWA as warranting investigation and treatment in symptomatic patients.
Symptoms With Ferritin 15 and Normal Haemoglobin
Because haemoglobin is maintained, patients with IDWA don't typically experience the classic anaemia symptoms of pallor or severe breathlessness at rest. Instead, they experience a subtler but equally debilitating pattern:
- Persistent fatigue — beyond what sleep fixes; cellular energy production is impaired
- Brain fog — difficulty concentrating, slowed thinking, forgetting words
- Hair thinning — diffuse shedding, reduced hair volume, thinning at the temples
- Reduced exercise tolerance — breathlessness or fatigue on exertion that wasn't there before
- Restless legs — often worse at night, closely linked to iron and dopamine metabolism
- Cold extremities — hands and feet that are disproportionately cold
- Low mood and irritability — iron depletion affects neurotransmitter synthesis
Why "Your Bloods Are Fine" Is Misleading
A common experience for patients with IDWA is being told their blood results are normal — because haemoglobin falls within range. This is accurate but incomplete. If ferritin isn't checked, or if the result is noted but not acted upon because Hb is normal, the underlying iron deficiency goes untreated.
At Lambert Medical Practice, we always review ferritin, TSAT, haemoglobin, and serum iron together — because no single marker tells the full story. A ferritin of 15 with a normal Hb is still a significant finding that warrants clinical decision-making.
Do You Need an Iron Infusion at Ferritin 15 with Normal Hb?
The short answer is: possibly, and it depends on your symptoms and TSAT. A few guiding principles:
Infusion likely appropriate
Significant symptoms + ferritin 15 + TSAT <20%, or previous tablets failed
Tablets reasonable first step
Mild symptoms, no gut condition, no prior tablet intolerance — with close monitoring
Discuss with your GP
Clinical history, cause of deficiency, and individual preference all inform the decision
Calculate Your Iron Requirement
Even with a near-normal haemoglobin, the Ganzoni Formula typically calculates a significant iron deficit at ferritin 15 — because 500 mg is added to replenish stores regardless of Hb, and even small Hb gaps produce meaningful mg requirements in most adults.
Use our free Iron Deficit Estimator to get a personalised estimate from your actual blood results: