Iron deficiency anaemia in adults

Red Flags

IDA with weight loss, change in bowel habit, rectal bleeding, dyspepsia, or family history of GI cancer — same-day endoscopy + colonoscopy under cancer pathway^[1]
Severe symptomatic anaemia (Hb <70 g/L with cardiac decompensation, syncope, dyspnoea) — admit; transfuse 1 unit at a time and reassess; IV iron post-stabilisation^[1]
Recurrent IDA despite repletion and no GI source — investigate menorrhagia, coeliac disease, H pylori, malabsorption, urinary loss, parasitic infection^[1]
Severe hypophosphataemia after IV ferric carboxymaltose — check phosphate at 1–2 weeks if symptomatic; replace; switch agent if recurrent^[1]

First-line treatment

Interventions

Identify and treat underlying cause^[1]
All adult IDA needs aetiology workup; do not just replete iron; coordinate gastroenterology, gynaecology, or other relevant specialty for definitive treatment
Diet counselling^[1]
Iron-rich foods (red meat where consumed, dark green leafy vegetables, pulses, fortified cereals); vitamin C with iron meal; avoid tea/coffee within 1 hour of iron tablet; address vegetarian/vegan deficiencies
Oral iron repletion (first-line)^[1]
100 mg elemental iron PO daily or alternate-day; alternate-day improves absorption per hepcidin physiology; continue until Hb normalises + 3 months to replenish stores; reassess Hb at 4–6 weeks
IV iron when oral fails or contraindicated^[1]
Indications: intolerance, non-response, ongoing blood loss, malabsorption (IBD, post-bariatric, coeliac), pre-operative repletion within 6 weeks, advanced CKD; ferric carboxymaltose convenient single-dose; iron sucrose multi-dose alternative

First-line drug therapy

Drug	Class	Adult	Paediatric	Notes
Ferrous sulphate^[1]	Iron salt (oral)	200 mg PO TDS (60 mg elemental iron each); or alternate-day single dose	Per local protocol	First-line oral iron; widely available, low cost; nausea, constipation common — alternate-day improves tolerance and absorption; iron polymaltose better tolerated alternative
Ferrous ascorbate^[1]	Iron salt with vitamin C (oral)	100 mg elemental iron PO BD	—	Indian-market alternative with claimed better absorption due to integrated ascorbic acid; well-tolerated; cost similar to ferrous sulphate
Ferric carboxymaltose (IV)^[1]	Parenteral iron — high-dose single infusion	750–1000 mg IV single dose; can repeat at 7 days for total iron deficit (max 2000 mg total)	—	Single-dose convenience; rapid repletion; phosphate decline at 1–2 weeks (rarely symptomatic); hypersensitivity rare
Iron sucrose (IV)^[1]	Parenteral iron — multi-dose	200 mg IV per session × 5 sessions to total dose calculated by Ganzoni formula	1–2 mg/kg per session	Widely available alternative; multiple sessions; lower hypersensitivity than older iron preparations
Iron isomaltoside / ferric derisomaltose (IV)^[1]	Parenteral iron — high-dose single infusion	Up to 20 mg/kg IV single infusion	—	Single-dose alternative to ferric carboxymaltose; lower phosphate decrement signal; hypersensitivity rare

Ferrous sulphate^[1]

Iron salt (oral)

Adult: 200 mg PO TDS (60 mg elemental iron each); or alternate-day single dose
Paediatric: Per local protocol

First-line oral iron; widely available, low cost; nausea, constipation common — alternate-day improves tolerance and absorption; iron polymaltose better tolerated alternative

Ferrous ascorbate^[1]

Iron salt with vitamin C (oral)

Adult: 100 mg elemental iron PO BD
Paediatric: —

Indian-market alternative with claimed better absorption due to integrated ascorbic acid; well-tolerated; cost similar to ferrous sulphate

Ferric carboxymaltose (IV)^[1]

Parenteral iron — high-dose single infusion

Adult: 750–1000 mg IV single dose; can repeat at 7 days for total iron deficit (max 2000 mg total)
Paediatric: —

Single-dose convenience; rapid repletion; phosphate decline at 1–2 weeks (rarely symptomatic); hypersensitivity rare

Iron sucrose (IV)^[1]

Parenteral iron — multi-dose

Adult: 200 mg IV per session × 5 sessions to total dose calculated by Ganzoni formula
Paediatric: 1–2 mg/kg per session

Widely available alternative; multiple sessions; lower hypersensitivity than older iron preparations

Iron isomaltoside / ferric derisomaltose (IV)^[1]

Parenteral iron — high-dose single infusion

Adult: Up to 20 mg/kg IV single infusion
Paediatric: —

Single-dose alternative to ferric carboxymaltose; lower phosphate decrement signal; hypersensitivity rare

Safety-net

Take iron tablet on an empty stomach with vitamin C (orange juice, citrus); avoid tea or coffee within an hour^[1]
Persistent fatigue, breathlessness, or recurrence of anaemia despite iron — return to your clinician for further investigation; do not just take more iron^[1]
Take iron for 3 months after Hb returns to normal — your iron stores need rebuilding even when blood count is fine^[1]

Referral criteria

Suspected GI source in IDA — men >50 or post-menopausal women, weight loss, bowel habit change, family history of GI cancerGastroenterology with endoscopy and colonoscopy under cancer pathway^[1]
Refractory IDA despite repletion or recurrent IDAGastroenterology / haematology for occult source workup^[1]
Heavy menstrual bleeding contributing to IDAGynaecology for AUB workup and tranexamic acid / hormonal therapy^[1]
Severe anaemia with cardiac compromiseEmergency department; transfusion and IV iron^[1]

Clinical summary

Diagnosis, oral and intravenous iron repletion, and aetiology workup for iron deficiency anaemia in non-pregnant adults.

References

1.ICMR Guidelines for Iron Deficiency Anaemia in Adults (2023); BSH Guidelines for the Laboratory Diagnosis of Iron Deficiency; AGA Clinical Practice Update on Anaemia in GI Disorders (2023)