Screen for severe thrombocytopenia, active bleeding, thrombotic microangiopathy (TTP/HUS), and DIC. These require emergency or same-day haematology.
Very low platelets warrant same-day haematology assessment even without bleeding, but the count alone does not determine bleeding risk — interpret it with bleeding symptoms, the rate of fall, other cell lines, coagulation, medication, comorbidity and any planned procedure. Treatment is cause-specific and specialist-led; prophylactic platelet transfusion is not routinely used in ITP, HIT or TTP (NICE NG24).
TTP (thrombotic thrombocytopenic purpura) is a life-threatening emergency caused by severe ADAMTS13 deficiency (BSH 2023). It often presents without the historical pentad, so suspect it from thrombocytopenia plus MAHA. Discuss immediately with the regional TTP/haematology service; send ADAMTS13 before plasma therapy if this does not delay treatment, but do not wait for the result.
HELLP syndrome (Haemolysis, Elevated Liver enzymes, Low Platelets) presents with epigastric pain, nausea and headache, often with hypertension or proteinuria. Low platelets alone in pregnancy are not HELLP — haemolysis and elevated liver enzymes are also required. It needs emergency obstetric assessment.
DIC (disseminated intravascular coagulation) consumes platelets and clotting factors. Triggered by sepsis, trauma, obstetric catastrophe, malignancy. Prolonged APTT/PT, low fibrinogen, raised D-dimer. Treat underlying cause (sepsis source control, delivery in AFLP).
Confirm true thrombocytopenia and exclude laboratory artefact (pseudothrombocytopenia). A single low platelet count may be spurious due to clumping.
Pseudothrombocytopenia is a laboratory artefact: EDTA (the anticoagulant in FBC tubes) causes platelet clumping in some patients, so automated counters undercount platelets. The film shows clumps, and a citrate (or lab-advised) sample gives the true count. No treatment is needed — but assume it only in a well patient without bleeding, other cytopenias or film abnormalities.
Blood film review is key in unexplained thrombocytopenia. It can show schistocytes (TTP/TMA/DIC), large young platelets (ITP), dysplasia or blasts (MDS, leukaemia), and platelet clumps (pseudothrombocytopenia) that automated counters cannot interpret.
Bleeding risk is not determined by the platelet count alone. Some patients with severe thrombocytopenia have little bleeding, whereas clinically important bleeding can occur at higher counts — depending on the cause and rate of fall, platelet function, anticoagulants/antiplatelets, coagulopathy, renal/liver disease, trauma and planned procedures, pregnancy, age and comorbidity.
Transient thrombocytopenia post-viral infection (EBV, dengue, COVID) is common. Counts usually recover as the infection settles; repeating the FBC per local pathway avoids unnecessary referral, but escalate if the count is falling, the patient is symptomatic or other cell lines are affected.
Classify thrombocytopenia by severity, mechanism (decreased production vs increased destruction), and whether other cell lines are affected.
Severity bands help prioritise but do not on their own define bleeding risk or the need for admission. Interpret the count with bleeding symptoms, rate of fall, other cell lines, coagulation, medication, comorbidity and any planned procedure; when platelets are falling rapidly, urgency is greater than the absolute count suggests.
Isolated thrombocytopenia (normal Hb/WCC) suggests peripheral destruction (ITP, TTP, drug-induced) rather than bone marrow failure. The marrow is producing platelets normally, but they're being destroyed in the spleen or by antibodies. Prognosis is better than pancytopenia.
Pancytopenia (low platelets + Hb + WCC) indicates bone marrow failure or infiltration. Urgent bone marrow biopsy differentiates aplastic anaemia (empty marrow, treat with immunosuppression), MDS (dysplastic marrow, supportive care ± chemotherapy), and acute leukaemia (blast infiltration, immediate chemotherapy).
Likely gestational thrombocytopenia is usually mild, isolated and late-onset, and resolves postpartum. New, falling or moderate thrombocytopenia in pregnancy requires obstetric/haematology assessment to exclude pre-eclampsia/HELLP, ITP, TTP, acute fatty liver and other secondary causes.
Examine for signs of bleeding, organomegaly, and underlying conditions causing thrombocytopenia.
Petechiae vs purpura vs ecchymoses: petechiae (pinpoint, non-blanching), purpura (larger) and ecchymoses (bruises) document bleeding but do not map reliably to a specific platelet count. Widespread or mucosal bleeding is more concerning than a few dependent petechiae on the legs.
Splenomegaly in thrombocytopenia suggests splenic sequestration (hypersplenism) or lymphoproliferative disease. In ITP the spleen is usually not enlarged; significant splenomegaly points to CML, lymphoma, myelofibrosis or portal hypertension rather than isolated ITP.
Hepatosplenomegaly with thrombocytopenia suggests chronic liver disease. Portal hypertension causes splenomegaly (congestive) and hypersplenism (splenic sequestration of platelets).
Fundoscopy may identify retinal haemorrhage in severe thrombocytopenia. Bleeding at a critical site such as the eye or brain needs urgent haematology discussion; transfusion decisions follow NICE NG24 and specialist advice.
Investigate based on severity, clinical context, and blood film findings. Target investigations to the likely differential diagnosis.
The blood film differentiates ITP (large young platelets), TTP/TMA (schistocytes — judged on morphology and clinical context rather than a fixed percentage), MDS (dysplastic cells), and pseudothrombocytopenia (platelet clumps). Without a blood film, you cannot confidently diagnose ITP.
Clotting screen differentiates isolated thrombocytopenia (ITP, normal PT/APTT) from DIC (prolonged PT/APTT, low fibrinogen) and liver disease (prolonged PT, normal APTT). In ITP, clotting is normal because clotting factors are unaffected; only platelet number is low.
TTP diagnosis: the full pentad is often absent, so do not wait for it. Suspect TTP/TMA with thrombocytopenia plus MAHA (schistocytes, raised LDH, low haptoglobin, indirect hyperbilirubinaemia, reticulocytosis). Severe ADAMTS13 deficiency confirms TTP, but specialist treatment starts before the result — send ADAMTS13 before plasma therapy if this does not delay treatment (BSH 2023).
ITP is a diagnosis of exclusion. Secondary causes (HIV, hepatitis, autoimmune disease, liver disease, drugs, immunodeficiency, TTP, MDS) are sought according to clinical context. With isolated thrombocytopenia, a normal film (apart from large platelets) and no secondary cause, haematology confirms the diagnosis; bone marrow examination is a specialist decision for atypical features.
Refer based on severity, bleeding risk, mechanism, and pregnancy status. Severe thrombocytopenia requires same-day haematology.
Platelets <10 × 10⁹/L require urgent same-day haematology assessment even if asymptomatic. Treatment depends on the cause and is specialist-led; in ITP, prophylactic platelet transfusion is not routinely given (NICE NG24).
TTP is a medical emergency. Discuss immediately with the regional TTP/haematology service for plasma therapy; do not wait for ADAMTS13 results or for the full pentad.
HIT (heparin-induced thrombocytopenia) is paradoxically prothrombotic despite low platelets. If suspected, stop all heparin (including flushes) immediately, assess with the 4Ts score, contact haematology urgently and start an appropriate non-heparin anticoagulant per the specialist/local protocol (options include argatroban, bivalirudin, fondaparinux with weight- and renal-function-dependent dosing, or a DOAC in selected patients). Do not wait for laboratory confirmation if probability is intermediate or high. Do not give platelet transfusions routinely — only for life-threatening bleeding or specialist-directed procedures (BSH HIT 2024).
Gestational thrombocytopenia is usually mild, isolated and late-onset; new, falling or moderate thrombocytopenia needs obstetric/haematology assessment to exclude pre-eclampsia/HELLP, ITP, TTP and acute fatty liver. Suitability for neuraxial anaesthesia depends on the cause, platelet trend, coagulation, bleeding history, obstetric context and local anaesthetic policy, and is decided by the obstetric anaesthetic and haematology/obstetric team rather than a fixed threshold.
Treatment depends on cause and severity. Treatment of ITP is haematology-led and depends on bleeding, platelet count, comorbidity, planned procedures and patient preference. Primary care should arrange urgent referral, manage bleeding emergencies and avoid medicines that worsen bleeding unless essential.
ITP treatment options (haematology-led — not a primary-care prescribing protocol):
Next steps: see Haematological cancers · Hypertension in pregnancy · DOACs, antiplatelets and anticoagulation
Not every patient with ITP needs treatment. Haematology decides whether to observe or treat based on bleeding, platelet count, comorbidity, planned procedures and patient preference; treatments have side effects and often only temporarily raise platelets.
IVIg saturates Fc receptors on splenic macrophages, reducing destruction of antibody-coated platelets. Specialists use it when a rapid rise is needed (bleeding, urgent procedure) or steroids are unsuitable.
Corticosteroids suppress autoantibody-mediated destruction, but relapse on tapering is common and prolonged use brings osteoporosis, diabetes, weight gain and immunosuppression — so courses are kept as short as possible under haematology direction.
Platelet transfusion in ITP is generally reserved for life-threatening bleeding or urgent specialist-directed intervention, because transfused platelets are rapidly destroyed by the same antibodies (NICE NG24).
Lifestyle modifications reduce bleeding risk in patients with chronic thrombocytopenia. Education on recognizing serious bleeding is critical.
NSAIDs and aspirin impair platelet function and may increase bleeding risk, but whether to avoid them depends on the platelet count and trend, bleeding symptoms, cause, concurrent anticoagulants and renal/GI/cardiovascular risk. Paracetamol has no antiplatelet effect; use usual liver and dose precautions.
Contact sports risk head trauma. Advice should reflect the cause and stability of thrombocytopenia, bleeding history, contact and head-trauma risk, anticoagulation and the specific sport, rather than a single platelet cut-off.
Heavy menstrual bleeding (menorrhagia) is common in thrombocytopenia. Tranexamic acid (antifibrinolytic) can reduce menstrual bleeding where appropriate, and the levonorgestrel IUS or hormonal options can reduce or suppress menstruation — discuss with haematology/gynaecology.
Recognising ICH early saves lives. Sudden severe headache, vomiting, confusion, focal weakness and seizures are red flags needing 999 assessment; teach every patient with significant thrombocytopenia these warning signs.
Monitor platelet trajectory, watch for bleeding, and re-refer if platelets falling or new symptoms. Chronic thrombocytopenia requires long-term surveillance.
Platelet trajectory matters as much as the absolute count: a steady rise suggests recovery, while fluctuating or falling counts need haematology review. When platelets fall rapidly, urgency is greater than the absolute count suggests.
Spontaneous remission can occur in ITP, especially after viral infection, which is why haematology may choose observation rather than treatment when there is no bleeding.
ICH risk is the primary concern in severe thrombocytopenia. Sudden severe headache in a thrombocytopenic patient is ICH until proven otherwise — call 999 for emergency assessment and imaging.
Chronic ITP (platelets <100 × 10⁹/L for >12 months) requires long-term haematology follow-up. Relapse after stopping treatment is common. Second-line therapies (rituximab, TPO agonists, splenectomy) have different risk-benefit profiles; shared decision-making with patient and haematologist is essential.