Anaemia - microcytic

Borders Ref Help Toolkit
NHS Borders

Definition:

Anaemia (haemoglobin below normal range) and microcytosis (MCV below normal range). 

The principle causes of a microcytic anaemia are iron deficiency, the anaemia of chronic disease, and thalassaemia:

  • A microcytic anaemia with a low ferritin (or serum iron low and transferrin ≥3.0 g/l on a fasting sample) establishes a diagnosis of iron deficiency anaemia.  In such cases, treat with oral iron supplements until the Hb normalises and then for an additional 3 months to replenish iron stores.  If the patient experiences side effects (often nausea or bowel disturbance), try alternative oral iron preparations such as Ferrous Sulphate, Ferrous Gluconate or Sodium Feredetate.  To enhance absorption of oral iron, please advise patients to take supplements with orange juice and avoid taking within 1 hour of meals, tea or coffee. If the patient is absolutely unable to tolerate any oral iron preparation, they should be referred for intravenous iron infusion..  Please consult separate iron deficiency anaemia pathway for further management. Consider what the underlying cause of iron deficiency is, and whether Gastroenterology referral is warranted.
  • The anaemia of chronic disease is diagnosed in patients with anaemia, low-normal or low MCV, normal or increased ferritin, raised ESR and low-normal/low iron and low-normal/low transferrin ≤3.0 g/l.  This is caused by chronic infective or inflammatory disorders.  In such cases, please consult separate anaemia-normocytic guidance for further management.
  • Thalassaemia is an inherited haemoglobinopathy commoner in people of SE Asian or Southern Mediterranean ancestry but may be seen in Caucasians.  It is diagnosed using Hb electrophoresis and other specialised analyses.  Testing can be requested via Haematology at BGH if this is suspected.

Who to refer, who not to refer, how to refer

Who to refer:

  • Iron deficiency anaemia where patient is completely intolerant of all oral iron preparations. If under a parent specialty for bleeding symptoms, or with a clear organ system cause for iron deficiency, referral should be directed to the appropriate specialty.
  • All cases of suspected haemoglobinopathy – see separate Inherited Red Cell Disorders guidance - link here.

Who not to refer:

  • Iron deficiency anaemia – consult separate iron deficiency anaemia pathway for further management.
  • Anaemia of chronic disorders – see definition above – follow separate normocytic anaemia guidance for further management.

How to refer:

SCI Gateway to Department of Haematology  BGH

Primary care management

Primary care investigations

  • Ferritin – if low, this indicates iron deficiency and please treat as above and consult separate iron deficiency anaemia pathway for further management.
  • If ferritin is normal or high, check iron and transferrin on a fasting blood sample (take sample in morning with nothing to eat and only water to drink since midnight), CRP and blood film
  • If serum iron is low and transferrin ≥3.0 g/l on a fasting sample, this is diagnostic of iron deficiency – treat as iron deficiency as above and consult separate iron deficiency anaemia pathway for further management.
  • If results show anaemia of chronic disorders – see definition above – please follow separate normocytic anaemia guidance for further management.

Editorial Information

Last reviewed: 17/01/2025

Next review date: 17/01/2027

Author(s): Charlotte Robertson.