12.2 Haematology: Anaemias & Blood Safety Monitoring
Key Takeaways
- Oral iron products must be compared by elemental iron content, not salt weight; a modified-release ferrous sulfate 325 mg tablet supplies about 105 mg elemental iron.
- Single daily or alternate-day iron dosing is now preferred over divided dosing because large doses raise hepcidin and block subsequent absorption.
- Oral iron should be separated by at least two hours from levothyroxine, tetracyclines, quinolones and bisphosphonates, and continued about three months after haemoglobin normalises.
- Iron deficiency in an adult man or postmenopausal woman requires medical investigation for blood loss rather than an over-the-counter supplement.
- Fever, sore throat, mouth ulcers or unexplained bruising in a patient taking clozapine, carbimazole, methotrexate or a thiopurine requires a same-day full blood count.
12.2 Haematology: Anaemias & Blood Safety Monitoring
Quick Answer: APC lists haematology as an exam content area. The pharmacist-level material is iron deficiency anaemia (elemental iron dosing, absorption interactions, duration), vitamin B12 and folate deficiency, when an anaemia demands investigation rather than a supplement, and recognising drug-induced blood dyscrasias early enough to prevent death.
Anaemia arrives at the pharmacy counter as tiredness, breathlessness on stairs, or a request for "iron tablets". Standard 3.1 expects you to assess whether a supplement is the right answer at all; Standard 3.3 expects you to interpret monitoring and act on danger signals.
Iron deficiency anaemia
Read elemental iron, not the salt weight
Oral iron products state a salt weight and an elemental iron content, and only the elemental figure is comparable across products. For example, a modified-release ferrous sulfate 325 mg tablet provides approximately 105 mg of elemental iron, while smaller ferrous fumarate or ferrous gluconate tablets provide considerably less. Always check the pack or AMH before comparing "strengths" for a patient.
Dosing principles that have changed
Traditional practice divided large daily doses across the day. Current evidence shows that a large dose raises hepcidin, which then blocks absorption of the next dose. Practical consequences:
- A single daily dose is usually preferred over divided dosing
- Alternate-day dosing can achieve comparable or better fractional absorption with fewer gastrointestinal adverse effects, and is a reasonable strategy for people who cannot tolerate daily iron
- Lower doses are often as effective as maximal doses for repletion
Administration and absorption counselling
| Point | Reason |
|---|---|
| Best absorbed on an empty stomach; take with food if nausea is limiting | Food reduces absorption but improves tolerance and therefore adherence |
| Vitamin C or a citrus drink may improve absorption | Ascorbate reduces iron to the better-absorbed ferrous form |
| Separate from tea, coffee, milk, calcium and antacids | These substantially reduce iron absorption |
| Separate by at least 2 hours from levothyroxine, tetracyclines, quinolones and bisphosphonates | Chelation reduces absorption of both medicines |
| Expect dark stools; that is harmless | Prevents alarm and unnecessary presentations |
| Constipation is common — address proactively | Adherence collapses without it |
| Continue for about 3 months after haemoglobin normalises | Replenishes iron stores, not just the haemoglobin |
Overdose warning: iron is one of the most dangerous accidental ingestions in small children. Every iron supply is a safe-storage counselling opportunity.
When iron is the wrong answer
Iron deficiency in an adult man or a postmenopausal woman is not a nutrition problem until proven otherwise — it requires medical investigation for a source of blood loss, including gastrointestinal malignancy. Refer rather than sell. Other referral triggers include anaemia with weight loss, rectal bleeding or melaena, dysphagia, a haemoglobin that will not respond to adequate therapy, or anaemia in pregnancy that has not been medically assessed.
Vitamin B12 and folate
| Deficiency | Typical Australian management | Pharmacist points |
|---|---|---|
| B12 — malabsorption / pernicious anaemia | Parenteral hydroxocobalamin | Intrinsic factor loss means oral replacement is unreliable; do not substitute a supermarket supplement |
| B12 — dietary or drug-related | Oral cyanocobalamin can be adequate | Long-term metformin and proton pump inhibitors reduce B12 status; consider it in a metformin-treated patient with new neuropathy or fatigue |
| Folate | Oral folic acid | Never treat a possible B12 deficiency with folate alone — folate can improve the blood picture while neurological damage progresses |
That last row is a genuine exam trap. Check and correct B12 before, or alongside, folate.
Anaemia of chronic disease and chronic kidney disease
In chronic kidney disease, reduced erythropoietin production drives anaemia. Management uses iron (often intravenous) and erythropoiesis-stimulating agents under specialist direction. The community role is adherence support, injection-technique and storage counselling for ESAs, monitoring reminders, and avoiding medicines that worsen the picture.
Drug-induced blood dyscrasias — the recognition skill
This is the highest-yield haematology material for a pharmacist because you meet the patient before the blood test does.
| Medicine | Dyscrasia risk | The symptom that must never be dismissed |
|---|---|---|
| Clozapine | Severe neutropenia / agranulocytosis | Fever, sore throat, flu-like illness — urgent full blood count, mandatory monitoring programme |
| Carbimazole / propylthiouracil | Agranulocytosis | Sore throat, mouth ulcers, fever — stop and get an urgent blood count |
| Methotrexate | Myelosuppression | Mouth ulcers, unexplained bruising, sore throat, breathlessness |
| Azathioprine / mercaptopurine | Myelosuppression (catastrophic with allopurinol) | Infection signs, bruising |
| Co-trimoxazole, sulfasalazine | Bone marrow suppression | Fever, sore throat, purpura |
| Anticoagulants and antiplatelets | Bleeding, not marrow failure | Melaena, haematuria, unusual bruising, sudden severe headache |
Counselling script that works for all of them: "If you get a fever, a sore throat, mouth ulcers or unusual bruising, do not wait — get a blood test the same day and tell them which medicine you take."
Interpreting the numbers a patient shows you
You do not need to be a haematologist, but you should be able to orient yourself:
- Haemoglobin — the anaemia itself
- Mean cell volume (MCV) — low suggests iron deficiency or thalassaemia; high suggests B12/folate deficiency, alcohol, or some medicines
- Ferritin — the practical iron store marker, but it rises with inflammation, so a "normal" ferritin in an inflamed patient does not exclude iron deficiency
- Neutrophils — the number that matters for clozapine, carbimazole and cytotoxic monitoring
- Platelets — low platelets change your OTC advice immediately (avoid aspirin and NSAIDs)
Exam mindset
Haematology stems reward the intern who refuses to treat a symptom in isolation. Ask why the anaemia exists, check what the medicines could be doing to the marrow, and escalate fever or bruising in an immunosuppressed patient instead of selling a lozenge. Remember the elemental iron rule, the two-hour separation from levothyroxine, the three-month continuation, and the folate-before-B12 trap.
A patient starting oral iron for iron deficiency anaemia also takes levothyroxine each morning. What is the most important administration advice?
A 64-year-old man asks for iron tablets after his GP mentioned he was 'a bit anaemic' at a recent check. He has had no investigations. What is the most appropriate action?
A patient taking carbimazole for hyperthyroidism telephones the pharmacy with a sore throat and fever that started overnight. What is the priority advice?
A patient with macrocytic anaemia has not yet had vitamin B12 measured. Why is it unsafe to start folic acid alone?