Haematology · Peripheral blood smear

Hypersegmented Neutrophils

Neutrophils with too many nuclear lobes — hypersegmented neutrophils, a hallmark of megaloblastic anaemia due to vitamin B12 or folate deficiency.

Blood smear showing neutrophils whose nuclei are divided into many small lobes among red cells
Hypersegmented neutrophils on a peripheral smear.Image: Prof. Osaro Erhabor, via Wikimedia Commons — CC BY-SA 4.0.

Written & reviewed by: Kinase Medical Team · Last reviewed: 30 September 2026 · Editorial policy

Key features

  • Neutrophils larger than normal with an excess of nuclear lobes. Cut-offs vary by source: Harrison's describes five or more lobes; other texts use more than five (6+).
  • Due to impaired DNA synthesis in granulocyte precursors in vitamin B12 or folate deficiency.
  • Accompanied by oval macrocytes (MCV usually >100 fL), anisocytosis and poikilocytosis.
  • May be the only clue in a patient who is not yet anaemic.
  • Severe cases can show leukopenia and thrombocytopenia (ineffective haematopoiesis).

Differential diagnosis

Differential diagnosis of Hypersegmented Neutrophils
ConditionHow to tell it apart
Non-megaloblastic macrocytosis (alcohol, liver disease, some drugs)Macrocytic red cells without megaloblastic change — hypersegmented neutrophils point instead to B12/folate deficiency.

How it appears in NEET PG

Usually shown with a macrocytic anaemia vignette (vegetarian diet, pregnancy, alcohol use or neurological signs); the question asks for the deficiency or the next test.

Frequently asked questions

How many lobes define a hypersegmented neutrophil?

Definitions differ: some textbooks use five or more lobes, others more than five. In practice, neutrophils with six or more lobes are clearly abnormal.

What causes hypersegmented neutrophils?

Most commonly vitamin B12 or folate deficiency, which impairs DNA synthesis in dividing precursors.

Which red cell change accompanies them?

Oval macrocytes (macro-ovalocytes), with the MCV usually above 100 fL.

Sources

  1. Harrison's Principles of Internal Medicine (textbook)
  2. Parakh N, Dewan P. Revisiting the hematological manifestations of vitamin B12 deficiency. Front Nutr 2026 (PMC review)
  3. Pathoma — Fundamentals of Pathology (review text)

Keep practising

For exam preparation and medical education only — not a substitute for clinical judgement, diagnosis or treatment of any patient.