Skip to main content

Health condition · Clinically reviewed

Anemia, MCV-guided workup and treatment that actually restores stores.

Anemia is the US spelling of anaemia. Same condition, same UK clinical approach - and for the primary UK page, see /conditions/anaemia.

Jump to treatment
A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE, BSH and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including oral and IV iron, B12 hydroxocobalamin and haematology thresholds.

Key facts

Anemia at a glance.

The essentials in plain English - thresholds, classification by red cell size, and the ladder of UK treatment.

  • What it is

    A haemoglobin below the age and sex-adjusted threshold - under 130 g/L in men, 120 g/L in non-pregnant women and 110 g/L in pregnancy.

  • US vs UK spelling

    Anemia is the US spelling. UK guidance uses anaemia - see our primary UK page at /conditions/anaemia for the same clinical content.

  • How it is classified

    By red cell size (MCV) - microcytic, normocytic or macrocytic - which points straight at the likely cause.

  • Most common cause

    Iron deficiency - from menstrual loss, gut bleeding, malabsorption or a diet low in bioavailable iron.

  • Serious causes

    Colorectal cancer, coeliac disease, chronic kidney disease and haemolysis all present with anemia and must be excluded.

  • Treatment ladder

    Treat the cause, replace the missing nutrient, escalate to IV iron or transfusion if severe or symptomatic.

Why this guide matters

A cause-first framework, not a supplement aisle.

Anemia is common and treatable - and every case has a story worth uncovering before reaching for iron tablets.

  • MCV points at the cause

    A microcytic picture almost always means iron. A macrocytic picture usually means B12 or folate. Order the right tests first time.

  • Iron deficiency needs an explanation

    In men or post-menopausal women it is a suspected cancer pathway - urgent OGD and colonoscopy until proven otherwise.

  • Replacement should restore stores

    Ferritin, not haemoglobin, is the true endpoint. Under-treatment guarantees relapse - IV iron shortens the road when tablets fail.

How the diagnosis is made

From first blood test to a clear plan.

The steps a UK GP or haematologist will normally follow, in order - so you know what to expect and why.

  1. 01

    Assessing

    Full blood count and MCV

    The starting point - confirms anemia and classifies it by red cell size to narrow the cause.

  2. 02

    Assessing

    Iron studies and ferritin

    Ferritin below 30 micrograms/L confirms iron deficiency. Transferrin saturation adds context in chronic disease.

  3. 03

    Assessing

    B12, folate and TFTs

    Essential when the MCV is high - vitamin B12, folate and thyroid function together explain most macrocytic pictures.

  4. 04

    Confirming

    Reticulocyte count and blood film

    A reticulocyte rise plus film changes points at haemolysis, marrow response or a primary blood disorder.

  5. 05

    Confirming

    Coeliac serology and U&E

    Anti-tTG antibodies for coeliac disease, renal function for anaemia of chronic kidney disease.

  6. 06

    Referral

    Gastro or gynae referral

    Iron deficiency in men or post-menopausal women needs OGD and colonoscopy. Menstrual loss needs a gynae review.

  7. 07

    Referral

    Haematology referral

    For haemolytic anemia, unexplained macrocytosis, suspected marrow disease or when transfusion or IV iron is being considered.

Typical timeline: a first blood test to a settled plan in one to four weeks.

Symptoms

What anemia actually feels like.

The classic mix of fatigue, breathlessness and pallor - and the features that mean it is time to seek urgent help.

  • Fatigue and low energy

    The commonest symptom - persistent tiredness that does not lift with rest is the classic presenting complaint.

  • Breathlessness on exertion

    Reduced oxygen-carrying capacity - stairs, hills and exercise feel harder than they used to.

  • Palpitations and tachycardia

    The heart works harder to compensate - a fast or pounding pulse at rest can be the first clue.

  • Pallor and cold hands

    Pale conjunctivae, nail beds and palms - and a persistent feeling of being cold.

  • Pica and restless legs

    Craving ice, chalk or starch, or restless legs at night - both point strongly at iron deficiency.

  • Glossitis and angular cheilitis

    A smooth, sore tongue and cracked mouth corners - typical of iron, B12 or folate deficiency.

  • Neurological symptoms

    Numbness, tingling or unsteady walking - a red flag for B12 deficiency needing urgent replacement.

  • Red flag - chest pain or collapse

    Severe symptomatic anemia with chest pain, syncope or heart failure is an emergency needing hospital assessment.

Treatment

How anemia is treated in the UK.

Oral iron or vitamin replacement first, IV iron and menstrual control next, transfusion and haematology-led therapy for severe or specialist cases.

  • Oral iron replacement

    Ferrous sulfate, fumarate or gluconate - alternate-day dosing improves absorption and reduces gut side effects.

  • IV iron infusion

    Ferric carboxymaltose or derisomaltose when oral iron fails, is not tolerated, or in CKD, IBD and pregnancy.

  • B12 hydroxocobalamin

    Intramuscular loading then maintenance - lifelong in pernicious anaemia or ileal disease. Oral B12 works for dietary deficiency.

  • Folic acid replacement

    Oral folic acid 5 mg daily for four months - always check B12 first to avoid masking neurological damage.

  • Menstrual control

    LNG-IUS, tranexamic acid or the combined pill to reduce heavy periods driving iron loss.

  • Erythropoiesis stimulators

    EPO analogues for anaemia of chronic kidney disease - specialist-led, with iron status corrected first.

  • Red cell transfusion

    Reserved for severe symptomatic anemia or acute blood loss - single-unit transfusion is the modern standard.

  • Haematology-led therapy

    Steroids, immunosuppression or splenectomy for autoimmune haemolysis; disease-specific care for thalassaemia and sickle cell.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP or haematologist knows your history and can tell you which parts apply to you. If in doubt, get seen.

  • NICE. Anaemia - iron deficiency (CKS).

  • NICE. Anaemia - B12 and folate deficiency (NG239).

  • British Society for Haematology (BSH). Guidelines on the diagnosis and management of iron deficiency and haemolytic anaemias.

  • NICE. Chronic kidney disease - management of anaemia (NG8).

Red flags

When anemia needs urgent attention.

Most anemia is manageable in primary care. These are the situations that are not - and where a specialist opinion is needed.

  • Iron deficiency in men or post-menopausal women

    A GI cancer must be excluded - urgent OGD and colonoscopy under the two-week wait pathway.

  • Rectal bleeding or altered bowel habit

    Anemia with any lower GI red flag is a suspected cancer referral until proven otherwise.

  • B12 deficiency with neurological signs

    Numbness, ataxia or cognitive change needs urgent hydroxocobalamin - delay causes irreversible damage.

  • Severe symptomatic anemia

    Chest pain, syncope, heart failure or Hb below 70 g/L needs same-day hospital assessment and possible transfusion.

  • Suspected haemolysis

    Jaundice, dark urine and a rising reticulocyte count point at haemolytic anaemia - urgent haematology input.

  • Pregnancy with Hb below 100 g/L

    Antenatal anaemia needs prompt iron replacement, and IV iron if oral therapy fails or the third trimester is close.

  • Pancytopenia

    Low haemoglobin plus low white cells and platelets is a marrow red flag - urgent haematology referral.

  • Weight loss or night sweats

    Anemia with B symptoms raises concern for lymphoma or other marrow infiltration.

  • Failure to respond to oral iron

    No Hb rise after four weeks means malabsorption, ongoing loss or the wrong diagnosis - rethink and refer.

Living with it

A treatable condition, with a clear ladder.

Four things that make the biggest difference day to day - treat the cause, give iron time, use diet as a helper, and escalate when tablets are not enough.

A quiet reminder

Ferritin is the endpoint, not haemoglobin alone.

A normal haemoglobin with an empty ferritin means relapse is coming - keep going until stores are refilled.

  1. 01 Cause

    Treat the cause, not just the number

    A low haemoglobin is a symptom - find the source of loss or the missing nutrient and the anemia follows.

  2. 02 Timing

    Give iron 8 to 12 weeks

    Haemoglobin recovers over weeks, ferritin over months - stay the course before deciding oral iron has failed.

  3. 03 Diet

    Diet helps, but rarely fixes deficiency

    Red meat, pulses, leafy greens and vitamin C aid absorption - but established deficiency needs replacement.

  4. 04 Escalate

    IV iron is safe and effective

    When oral iron does not work or is not tolerated, a single IV infusion often restores stores in one visit.

Frequently asked

Everything we get asked about anemia.

Quick answers on classification, iron, B12, IV replacement and transfusion.

  • What is anemia?

    Anemia is a haemoglobin concentration below the normal range for age and sex - under 130 g/L in men, 120 g/L in non-pregnant women and 110 g/L in pregnancy. It reflects reduced oxygen-carrying capacity of the blood and always has an underlying cause worth identifying. Anemia is the US spelling of anaemia and the two terms mean the same thing.

  • What is the difference between anemia and anaemia?

    None clinically - only the spelling. Anemia is the US form and anaemia is the UK form. UK guidance, NHS pages and our primary condition page all use anaemia. This page mirrors that content for readers searching the US spelling.

  • How is the cause of anemia worked out?

    By classifying the anemia by red cell size on a full blood count. Microcytic points at iron deficiency or thalassaemia. Normocytic points at chronic disease, acute blood loss or haemolysis. Macrocytic points at B12 or folate deficiency, hypothyroidism, alcohol or certain drugs. Iron studies, B12, folate, thyroid function and a blood film then narrow it further.

  • When is IV iron used instead of tablets?

    When oral iron has failed, is not tolerated, or where absorption is unreliable - inflammatory bowel disease, coeliac disease, chronic kidney disease, heart failure or the third trimester of pregnancy. A single infusion of ferric carboxymaltose or derisomaltose can replace months of tablets in one visit.

  • Is a low haemoglobin always serious?

    Not always, but it always needs an explanation. Mild anemia may be well tolerated, especially if it has developed slowly. Severe symptomatic anemia, or iron deficiency in men or post-menopausal women, always needs prompt investigation to exclude serious causes including gastrointestinal cancer.

  • What is haemolytic anemia?

    A group of conditions where red cells are destroyed faster than the marrow can replace them. Causes include autoimmune disease, inherited red cell disorders such as hereditary spherocytosis, enzyme deficiencies like G6PD, and haemoglobinopathies including sickle cell disease and thalassaemia. It is diagnosed with reticulocyte count, blood film, haptoglobin, LDH and a direct antiglobulin test, and managed by a haematologist.

Related content

Keep reading.

Pulse Healthcare concierge

Send us your enquiry

A concierge service for UK private healthcare. We match you with the best vetted clinics and consultants in our network - they then contact you directly.

So we can match you to the right clinician close to you.

We reply to every enquiry within 24 hours (Mon–Fri). Confidential - your details are never shared outside our vetted consultant network.