|
REASONING GP · Clinical algorithm · Quick reference
Anaemia in adults — triage and diagnostic approachThe MCV narrows the cause, but the question that changes outcomes is where is the blood going. Iron deficiency in a man or postmenopausal woman is a GI cancer question until answered.
|
Page 1 / 2 |
| Trigger / red flag | Leading concern · destination | Do now · do not delay |
|---|---|---|
| Compromise at any Hb: chest pain, breathlessness at rest, syncope, pulse above 100, systolic BP below 90, new confusion or heart failure · Hb below 70 g/L or a rapid fall from a recent normal · active bleeding — haematemesis, melaena, large-volume rectal bleeding, or heavy menstrual loss with a postural drop. Or anaemia with an abnormal second or third cell line: neutropenia, thrombocytopenia, pancytopenia, blasts or abnormal cells on the film, a very high or very low white count; or anaemia with fever, bruising, petechiae, bone pain, night sweats or lymphadenopathy. | Decompensated anaemia · GI bleed · haemorrhagic menstrual loss Emergency admission now Acute leukaemia · myelodysplasia · marrow infiltration · aplastic anaemia 999 or same-day haematology discussion — immediate if febrile or with blasts |
Take ferritin, B12 and folate before any transfusion or iron — once treated the cause may be unrecoverable. ECG if there is chest pain: anaemia precipitates ischaemia. Observations with postural BP. Stop NSAIDs, but discuss anticoagulation with the receiving team rather than stopping it unilaterally. Do not start a PPI and review after melaena, or prescribe oral iron and review a compromised patient. This is not "anaemia" — it is a marrow problem, and it does not go in a routine iron pathway. Speak to haematology the same day; a patient with blasts, neutropenic fever or rapidly falling counts needs admission now. Do not start iron, B12 or folate while awaiting that discussion, and do not repeat the FBC in a month. |
| Suspected haemolysis — jaundice with dark urine, a rapid fall in Hb, splenomegaly, high reticulocytes, raised LDH and bilirubin with low haptoglobin; a new drug or known haemoglobinopathy. Or B12 deficiency with neurological features — paraesthesiae, numbness, unsteady gait, cognitive change or sore tongue, with or without anaemia or a macrocytosis. | Haemolytic anaemia · subacute combined degeneration of the cord — irreversible if untreated Same-day haematology advice; admission if the Hb fall is rapid |
Haemolysis: send reticulocytes, LDH, bilirubin, haptoglobin, a film and a direct antiglobulin test together, stop the suspected drug, and judge urgency by the tempo of the fall rather than the absolute value. B12 with neurology: do not wait for the results or the intrinsic factor antibody, and never give folate first — folate alone can worsen the neurological damage. Give hydroxocobalamin by the neurological regimen (1 mg IM on alternate days until no further improvement, then 1 mg every 2 months, BNF), taking B12, folate and intrinsic factor antibody before the first dose. |
| Pregnancy — Hb below 110 g/L in the first and third trimesters, below 105 in the second, below 100 postpartum. Or a cause on the drug chart or history: NSAIDs, aspirin, anticoagulants, steroids, PPIs and metformin (B12), methotrexate; coeliac disease; bariatric or bowel surgery; dialysis; unsupplemented vegan diet. | Anaemia of pregnancy · drug-related loss or malabsorption · coeliac disease · CKD anaemia 999 if bleeding or compromised Same-day maternity or drug review |
Pregnancy: speak to maternity rather than managing alone — there is fetal and delivery risk, and postpartum Hb below 80 g/L needs same-day obstetric review. Start oral iron where deficiency is confirmed and refer for IV iron if oral is not tolerated, absorption is poor or delivery is near; a normal ferritin does not exclude deficiency late on. Otherwise: send coeliac serology in every unexplained iron deficiency — common, treatable and frequently missed — check eGFR, since CKD anaemia needs iron repletion before an erythropoietin-stimulating agent (NG8), and stop or review the culprit drug. |
| Iron-deficiency anaemia with an NG12 criterion: any man with iron-deficiency anaemia · any woman 55 or over who is postmenopausal with iron-deficiency anaemia · iron deficiency with rectal bleeding, a change in bowel habit, weight loss or an abdominal mass · dysphagia at any age · 55 or over with upper abdominal pain, reflux or dyspepsia plus weight loss · 60 or over with weight loss and new diabetes, nausea or bowel change · anaemia with bruising, petechiae or bone pain. | Colorectal · upper GI · urological · haematological cancer Urgent suspected-cancer referral or direct-access test within 2 weeks · NICE NG12 |
Match the test to the criterion (NG12): iron-deficiency anaemia in a man, or in a postmenopausal woman, is a colorectal urgent suspected-cancer referral — offer FIT to guide but never let a negative FIT override strong clinical suspicion · urgent direct-access OGD for dysphagia, or at 55 and over with weight loss plus upper abdominal pain, reflux or dyspepsia · very urgent FBC within 48 hours if leukaemia is possible · protein electrophoresis with Bence Jones protein at 60 and over · consider a renal tract cause. Investigate both ends of the gut. |
REASONING GP · Anaemia in adults — triage and diagnostic approach |
Page 2 / 2 |
| Iron deficiency low MCV, low ferritin | The commonest anaemia, and always a question about a source. Premenopausal women: menstrual loss is the usual cause — quantify it (flooding, clots, duration) and treat, but still send coeliac serology and consider GI loss where there are GI symptoms or a poor response. Men and postmenopausal women: GI blood loss until excluded — an NG12 colorectal referral. Also coeliac disease, NSAIDs, bariatric surgery, poor diet and urinary loss. But a low MCV with a normal ferritin and a normal or raised red cell count is thalassaemia trait — often strikingly low, with family origin from the Mediterranean, Middle East, South Asia, Africa or South-East Asia — needing a haemoglobinopathy screen and genetic counselling, not iron, which risks overload. |
| Chronic disease and CKD (normocytic), B12 and folate (macrocytic) | Chronic disease: inflammation, infection, malignancy or autoimmune disease with a normal or raised ferritin and a low transferrin saturation — treat the underlying disease, and never accept the label without excluding deficiency and myeloma. CKD: common once eGFR falls; iron stores must be repleted before an erythropoietin-stimulating agent (NG8). B12: pernicious anaemia, gastric or ileal surgery, Crohn's, metformin and long-term PPIs, vegan diet — neurological features mean treat today and never give folate first. Folate: poor diet, alcohol, pregnancy, haemolysis, methotrexate, coeliac disease. Check both together. |
| Marrow and haemolytic causes, and what not to conclude | Myelodysplasia — unexplained macrocytosis in an older patient, often with a low white count or platelets; myeloma — anaemia with renal impairment, bone pain and a raised ESR; leukaemia or infiltration — blasts or pancytopenia; haemolysis — high reticulocytes, raised LDH and bilirubin, low haptoglobin. All are haematology routes, and none responds to iron. Do not conclude: "iron deficiency — start iron" with no source sought in a man or postmenopausal woman · "chronic disease" without excluding deficiency and myeloma · "dietary" over 50 · "menorrhagia" without quantifying the loss or checking coeliac serology · or iron for a low MCV with a normal ferritin, which is probably thalassaemia trait. |
| Answer "where is the blood going", then prescribe | Send the whole panel and apply the NG12 criteria before starting iron. In a man or a postmenopausal woman the referral goes today and the iron starts alongside it, not instead of it: iron prescribed without a source sought is how GI cancer is missed here. Then the iron: one tablet of ferrous sulfate 200 mg (or fumarate or gluconate) daily is usually enough, and alternate-day dosing improves absorption and tolerance. Take with vitamin C, away from tea, coffee, calcium, PPIs and levothyroxine; warn about black stools and constipation. Expect the Hb to rise by at least 10 g/L in 4 weeks — if not, question adherence, dose, absorption or ongoing loss and escalate. Continue 3 months after the Hb normalises. |
| B12 and folate (order matters), and heavy menstrual bleeding | Never give folate alone in macrocytic anaemia until B12 is known — it can worsen neurological damage. Treat B12 first: hydroxocobalamin IM per the BNF, using the neurological regimen if there are neurological features, with lifelong maintenance in pernicious anaemia or after ileal or gastric surgery; then folate, and review metformin and PPIs. Heavy menstrual bleeding: treat the loss as well as the anaemia — tranexamic acid, an NSAID, a hormonal option or the levonorgestrel intrauterine system (NG88) alongside iron — but still send coeliac serology and reconsider GI loss if there are GI symptoms, a poor response, or she is over 50. |
| Recheck, the escalation rule, and what not to do | Recheck: FBC and ferritin at 4 weeks, then 3 months, then 3 months after stopping — with the triggers written down: chest pain, breathlessness at rest, syncope, melaena or heavy bleeding → emergency admission; Hb falling, no response at 4 weeks, or a new white-count or platelet abnormality → urgent specialist route. Do not: start iron before the haematinics are taken · give iron for a low MCV with a normal ferritin (screen for thalassaemia) · treat an abnormal white count or platelet count with iron · give folate before B12 · accept a normal MCV or a normal ferritin in inflammation as excluding deficiency · stop at a normal colonoscopy with the upper GI tract unexamined · or file iron deficiency in a man with no referral. |