Blood Tests for Anaemia: The Complete Guide
Anaemia affects over 1.6 million Australians. The right blood tests don't just confirm anaemia — they identify the type and underlying cause, which determines the correct treatment.
What Is Anaemia and Why Does It Matter?
Anaemia means your blood doesn't have enough healthy red blood cells or haemoglobin to carry adequate oxygen to your body's tissues. It is not a disease itself but a sign of an underlying problem — which is why identifying the type of anaemia through specific blood tests is critical for correct treatment.
The World Health Organization defines anaemia as haemoglobin below 130 g/L in men and below 120 g/L in non-pregnant women. In pregnancy, the threshold is 110 g/L due to normal haemodilution. However, these are population-level cutoffs — some individuals may be symptomatic with “normal” haemoglobin if their personal baseline is higher.
In Australia, anaemia is particularly prevalent in women of reproductive age (due to menstrual blood loss), pregnant women, older adults, Aboriginal and Torres Strait Islander communities, and people with chronic diseases. Iron deficiency alone accounts for about half of all anaemia cases globally, but treating iron deficiency when the actual cause is B12 deficiency or chronic disease can be ineffective or even harmful — which is why a systematic blood test approach matters.
The Full Blood Count: Your First Clue
The full blood count (FBC) is the starting point for every anaemia investigation. It measures haemoglobin (how much oxygen your blood can carry), MCV (the size of your red blood cells), and several other parameters that help classify the type of anaemia. MCV is the single most important clue — it splits anaemia into three categories that guide all further testing.
| Marker | Normal Range | Low Means | High Means |
|---|---|---|---|
| Haemoglobin (Hb) | 130–170 g/L (men), 120–150 g/L (women) | Anaemia — reduced oxygen-carrying capacity | Polycythaemia, dehydration, chronic lung disease |
| MCV (Mean Cell Volume) | 80–100 fL | Microcytic: iron deficiency, thalassaemia | Macrocytic: B12/folate deficiency, alcohol, liver disease |
| MCH (Mean Cell Haemoglobin) | 27–32 pg | Hypochromic: iron deficiency, thalassaemia | Macrocytic anaemias (B12, folate) |
| Ferritin | 30–300 µg/L (men), 30–200 µg/L (women) | Iron deficiency (below 30 is diagnostic) | Inflammation, infection, iron overload, liver disease |
| Reticulocyte Count | 0.5–2.5% | Bone marrow not responding (production problem) | Bone marrow compensating (blood loss or haemolysis) |
| RDW (Red Cell Distribution Width) | 11.5–14.5% | Uniform cell size (normal) | Mixed cell sizes: iron deficiency, B12/folate deficiency |
5 Types of Anaemia and Their Blood Tests
Iron Deficiency Anaemia
How it's diagnosed: Iron deficiency is the most common cause of anaemia worldwide and in Australia. Iron is essential for haemoglobin production — without it, red blood cells become small (microcytic) and pale (hypochromic), carrying less oxygen to tissues. Ferritin is the most sensitive early marker — it reflects total body iron stores and drops well before haemoglobin falls. A ferritin below 30 µg/L is diagnostic of iron deficiency, even if haemoglobin is still normal. Transferrin saturation below 20% confirms insufficient iron delivery to the bone marrow.
Common causes: Blood loss is the most common cause in adults — heavy menstrual periods in women, gastrointestinal bleeding (ulcers, polyps, colon cancer) in men and post-menopausal women. Other causes include inadequate dietary intake (vegetarians, vegans, restrictive diets), malabsorption (coeliac disease, inflammatory bowel disease, gastric bypass surgery), pregnancy (increased demand), and frequent blood donation.
Australian context: Iron deficiency affects approximately 12% of Australian women of reproductive age and up to 20% of pregnant women. The RCPA recommends ferritin as the first-line test for suspected iron deficiency. Iron studies are bulk billed under Medicare when requested by your GP with a clinical indication such as fatigue, heavy periods, or suspected dietary deficiency.
Vitamin B12 Deficiency Anaemia
How it's diagnosed: Vitamin B12 (cobalamin) is essential for DNA synthesis and red blood cell maturation. When B12 is deficient, red blood cells become abnormally large (macrocytic) because they cannot divide properly. The bone marrow produces fewer, larger cells that are less effective at carrying oxygen. B12 deficiency also causes neurological damage — peripheral neuropathy, balance problems, and cognitive decline — which can become permanent if not treated. Serum B12 below 150 pmol/L is deficient; 150–250 pmol/L is borderline and should be followed up with homocysteine or methylmalonic acid (MMA) which are more sensitive functional markers.
Common causes: Pernicious anaemia (autoimmune destruction of intrinsic factor, needed for B12 absorption) is the most common cause in older Australians. Other causes include strict vegan or vegetarian diets (B12 is found almost exclusively in animal products), malabsorption from coeliac disease or Crohn’s disease, gastric surgery or prolonged use of proton pump inhibitors (PPIs like omeprazole and pantoprazole which reduce stomach acid needed for B12 absorption), and metformin use in diabetics.
Australian context: B12 deficiency is particularly common in older Australians — approximately 10–15% of people over 60 have low B12 levels due to reduced stomach acid production. The RCPA notes that serum B12 has limited sensitivity, and functional markers (homocysteine, MMA) should be checked when B12 is borderline. B12 testing is bulk billed under Medicare. Treatment is typically intramuscular B12 injections (if absorption is impaired) or high-dose oral supplements.
Folate Deficiency Anaemia
How it's diagnosed: Folate (vitamin B9) works closely with B12 in DNA synthesis and red blood cell production. Deficiency produces the same macrocytic picture as B12 deficiency — large, immature red blood cells. However, folate deficiency does NOT cause the neurological damage seen with B12 deficiency. Serum folate reflects recent dietary intake (it can normalise after a single good meal), so red cell folate is a more reliable marker of long-term folate status. It is critical to check B12 before treating folate deficiency — giving folate alone to someone with undiagnosed B12 deficiency can mask the anaemia while neurological damage progresses silently.
Common causes: Inadequate dietary intake (folate is found in leafy green vegetables, legumes, and fortified cereals), alcohol excess (impairs folate absorption and metabolism), pregnancy (folate requirements double), malabsorption disorders (coeliac disease), and certain medications including methotrexate, trimethoprim, and some anti-epileptic drugs which interfere with folate metabolism.
Australian context: Since 2009, Australia has mandated folic acid fortification of bread-making flour, which has significantly reduced neural tube defects and population-level folate deficiency. However, deficiency still occurs in people with alcohol use disorders, malabsorption, and those on folate-depleting medications. Folate testing is bulk billed under Medicare. The RCPA recommends checking both B12 and folate together when macrocytic anaemia is identified.
Anaemia of Chronic Disease
How it's diagnosed: Anaemia of chronic disease (ACD) is the second most common type of anaemia after iron deficiency. It occurs when chronic inflammation — from infection, autoimmune disease, cancer, or chronic kidney disease — disrupts iron metabolism. Inflammatory cytokines increase hepcidin production, which blocks iron absorption from the gut and traps iron inside storage cells (macrophages). The result is a paradox: the body has adequate iron stores (ferritin is normal or elevated) but cannot use them effectively. This distinguishes ACD from true iron deficiency, where ferritin is genuinely low.
Common causes: Any chronic inflammatory condition: rheumatoid arthritis, lupus, inflammatory bowel disease, chronic infections (tuberculosis, HIV, hepatitis), chronic kidney disease (reduced erythropoietin production), cancer (both the disease itself and chemotherapy), and heart failure. The anaemia is usually mild to moderate and improves when the underlying condition is treated.
Australian context: ACD is commonly seen in hospital settings and in patients with chronic conditions managed by GPs. The diagnostic challenge is distinguishing ACD from iron deficiency when they coexist (which is common). Ferritin above 100 µg/L with low transferrin saturation and elevated CRP/ESR points to ACD. The RCPA recommends checking CRP alongside iron studies when chronic disease is suspected. All these tests are bulk billed under Medicare.
Haemolytic Anaemia
How it's diagnosed: Haemolytic anaemia occurs when red blood cells are destroyed faster than the bone marrow can replace them. The hallmark is an elevated reticulocyte count (the bone marrow is working overtime to compensate), elevated LDH and bilirubin (released from destroyed red cells), and low haptoglobin (consumed by binding free haemoglobin). The blood film often shows fragmented red cells (schistocytes) or spherocytes depending on the cause.
Common causes: Autoimmune haemolytic anaemia (warm or cold antibody types), hereditary conditions (thalassaemia trait is common in Australians of Mediterranean, Middle Eastern, South-East Asian, and African descent), infections (malaria, Clostridium), medications (some antibiotics, methyldopa), mechanical causes (prosthetic heart valves, microangiopathic conditions like TTP/HUS), and hypersplenism.
Australian context: Australia’s multicultural population means thalassaemia trait is relatively common — approximately 5% of Australians of Mediterranean, South-East Asian, or Middle Eastern ancestry carry a thalassaemia gene. Thalassaemia carriers often have mild microcytic anaemia that is mistakenly treated with iron supplements. A haemoglobin electrophoresis or gene test is needed to confirm the diagnosis. The DAT (Coombs test) and haemolysis markers are bulk billed under Medicare when clinically indicated.
When Anaemia Is Urgent: Know the Severity Levels
Not all anaemia requires urgent treatment. Your haemoglobin level and symptoms together determine how quickly you need medical attention. Here is a guide based on RCPA and WHO criteria:
Hb 100–120 g/L (women) or 100–130 g/L (men)
Symptoms: Mild fatigue, slight pallor, exercise intolerance
Action: GP review within 1–2 weeks. Identify and treat the cause.
Hb 70–100 g/L
Symptoms: Pronounced fatigue, breathlessness on exertion, pale skin, dizziness, rapid heartbeat
Action: Urgent GP review within days. Needs investigation. May need specialist referral.
Hb 50–70 g/L
Symptoms: Severe fatigue at rest, breathlessness, chest pain, tachycardia, confusion
Action: Same-day medical review or ED. May require blood transfusion.
Hb Below 50 g/L
Symptoms: Cardiovascular collapse risk, severe breathlessness, altered consciousness
Action: Emergency (call 000). Blood transfusion required. ICU monitoring may be needed.
What to Ask Your GP
Script for your GP appointment:
“I've been experiencing fatigue / breathlessness / dizziness / pale skin / heavy periods and I'd like to be checked for anaemia. Could we start with a full blood count and iron studies? If my MCV is abnormal, could we also check B12 and folate?”
Full Blood Count (FBC) with reticulocyte count
Iron Studies (ferritin, serum iron, transferrin, TIBC)
Vitamin B12 and Folate
CRP (to distinguish iron deficiency from chronic disease anaemia)
Coeliac serology (if malabsorption suspected)
Haemoglobin electrophoresis (if thalassaemia suspected)
Anaemia Blood Test Reference Panel
| Test | Purpose | Cost (Australia) |
|---|---|---|
| Full Blood Count (FBC) | Haemoglobin, MCV, MCH, RDW, reticulocytes | Bulk billed |
| Iron Studies (Ferritin, Iron, Transferrin, TIBC) | Diagnose iron deficiency vs chronic disease anaemia | Bulk billed |
| Vitamin B12 | Diagnose B12 deficiency causing macrocytic anaemia | Bulk billed |
| Serum Folate / Red Cell Folate | Diagnose folate deficiency causing macrocytic anaemia | Bulk billed |
| Reticulocyte Count | Assess bone marrow response | Bulk billed |
| CRP / ESR | Distinguish iron deficiency from chronic disease anaemia | Bulk billed |
| Blood Film (Peripheral Smear) | Visual assessment of red cell morphology | Bulk billed |
| Haemoglobin Electrophoresis | Screen for thalassaemia and haemoglobin disorders | Bulk billed* |
| Haptoglobin, LDH, Bilirubin | Haemolysis markers | Bulk billed |
| Coeliac Serology (tTG antibodies) | Screen for coeliac disease causing malabsorption | Bulk billed |
* Haemoglobin electrophoresis is bulk billed when ordered with a clinical indication such as unexplained microcytic anaemia, family history of thalassaemia, or ethnicity-based screening.
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Reference ranges sourced from the Royal College of Pathologists of Australasia (RCPA) and WHO guidelines. SmarterBlood provides health information and AI-powered blood test analysis. It is not a substitute for professional medical advice, diagnosis, or treatment.