Reasoning GP · Algorithm · 1-page summary
Normocytic anaemia (MCV 80–100 fL) in adults
For: adults with a low Hb and MCV 80–100 fL, in hours or OOH; pregnancy thresholds included. Not for: children. Raised or low MCV → macrocytosis or microcytosis algorithms; known sickle cell disease → its protocol.
Core rule: anchor on the reticulocytes and film, not the MCV. High reticulocytes = bleeding or haemolysis; low/normal = underproduction. Fragments + low platelets = emergency. Iron only when deficiency is documented.
0Stop — call 999 now
- Severe or rapidly progressive anaemia with chest pain, syncope, haemodynamic instability, acute dyspnoea, confusion or active bleeding → 999
- Suspected microangiopathic haemolysis (TTP/HUS) — anaemia + low platelets, fragments, neuro symptoms, renal impairment or fever (full pentad not needed) → immediate hospital/haematology Same-day — now; do not wait for ADAMTS13.
- While waiting: do not delay transfer to plan a transfusion in primary care.
1Triage — the whole FBC, film and reticulocytes
| Finding | Action |
|---|---|
| Blasts, febrile neutropenia | Or active bleeding, severe thrombocytopenia, rapidly progressive cytopenias → Same-day hospital/haematology |
| Stable pancytopenia | Repeat FBC + film, reticulocytes, medication review → Urgent haematology |
| High reticulocytes | Bleeding or haemolysis: LDH, haptoglobin, bilirubin, DAT. Stable, DAT positive (?AIHA) → Urgent haematology discussion |
| Low/normal reticulocytes | Underproduction (chronic disease, CKD, early iron deficiency, marrow) → block 3 |
2Screen — serious causes
- Sickle cell disease with severe pain, fever, hypoxia, chest or neuro symptoms, acute anaemia, big spleen, priapism or persistent vomiting → Same-day hospital.
- Weight loss, lymphadenopathy, night sweats, hepatosplenomegaly → consider a suspected cancer pathway referral (NG12) Urgent.
- Iron-deficiency anaemia, or anaemia aged 60+ even without iron deficiency → offer FIT; ≥10 µg Hb/g → colorectal suspected cancer pathway Urgent.
- Pregnancy (Hb <110 g/L 1st trimester, <105 later): severe, symptomatic or rapid fall, or Hb <100 g/L near delivery → Urgent obstetric advice.
3Assess — initial set for all
☐ Repeat FBC + differential, trends ☐ Reticulocytes ☐ Film if unexplained, progressive, other cytopenias or ?haemolysis ☐ Ferritin + CRP (TSAT if ferritin may mislead) ☐ U&E/eGFR, LFTs + bilirubin, urinalysis ☐ B12/folate, TSH, pregnancy test, coeliac serology where indicated ☐ Bleeding, drug, diet, alcohol and family history
Paraprotein, HIV, haemoglobinopathy tests and imaging only as findings guide.
4Classify — reticulocytes, ferritin with CRP, eGFR
- Chronic disease/inflammation — ferritin normal or high, low TIBC, raised CRP → treat the disease.
- Early iron deficiency — ferritin <30 µg/L → oral iron and find the source.
- CKD — not from eGFR alone: >60 investigate other causes; 30–60 use judgement; <30 CKD more likely, still consider others.
- Haemolysis — high reticulocytes, raised LDH and unconjugated bilirubin, low haptoglobin; DAT.
- Mixed deficiency — iron + B12/folate can give a normal MCV → check all three.
- Uncertain — no response after 4–6 weeks of treatment, or dysplasia/?MDS → Urgent haematology.
5Treat today — doses: NICE/SPC, BNF, local formulary
- Iron deficiency (confirmed): one oral tablet daily giving ~50–100 mg elemental iron; alternate days if not tolerated; continue 3 months after Hb normalises.
- B12: take samples first; neuro symptoms or severe megaloblastic anaemia → start IM hydroxocobalamin now, do not wait. Treat B12 before folate.
- Folate deficiency: folic acid 5 mg daily (commonly 4 months) once B12 is checked or treated.
- Chronic disease alone: no iron, B12, folate or EPO. ESA or roxadustat only via the renal team.
6Refer routinely — and follow up
- Gastroenterology: iron-deficiency anaemia in men and post-menopausal women → bidirectional GI investigation (BSG 2021).
- Renal team: CKD anaemia that is persistent, symptomatic, severe, in advanced CKD, or needs IV iron, ESA or HIF-PHI.
- Follow-up: Hb at 2–4 weeks on iron; no response at 4 weeks despite adherence → reassess (blood loss, coeliac, diagnosis), then IV iron via hospital pathway.
7Never reassure by
- A normal ferritin with inflammation, infection, CKD, malignancy, liver disease or obesity.
- A normal MCV — mixed iron and B12/folate deficiency hides both.
- A low eGFR as the whole explanation, especially with eGFR >60.
- A negative FIT when symptoms persist or there is a rectal/abdominal mass.
- Empirical iron instead of assessing for marrow disease.
- Folic acid while B12 status is unknown (cord damage).
8Safety-net — say it, then document it
999 “Call 999 for chest pain, fainting or collapse, severe breathlessness, new confusion, vomiting blood or heavy bleeding from the back passage.” A&E now “Fever if you have low white cells or sickle cell disease.” Same day “Contact us or NHS 111 today for worsening breathlessness, palpitations, black tarry stools or other rectal bleeding, yellow skin or dark urine, new bruising or bleeding, or new neurological symptoms.”
Remote or OOH: any of these → same-day face-to-face assessment; do not wait for the routine blood test or appointment.
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies
Reticulocytes and film reviewed: no blasts, fragments or unexplained cytopenias
Ferritin with CRP, renal function, B12/folate as indicated; FIT if due
Cause treated (B12 before folate); Hb recheck date and owner set
Safety-net given and documented
Summary of the full Reasoning GP normocytic anaemia algorithm, which holds the detail on haemolysis, CKD anaemia, sickle cell and pregnancy. Sources: NICE NG12 (updated April 2026), NG203, NG239, CG143; BSG IDA 2021; BSH iron deficiency in pregnancy; MHRA; local formulary. Clinical reference — follow local haematology pathways and check doses: NICE/SPC, BNF.