Iron-deficiency anaemia: what investigations do I need?

Why iron-deficiency anaemia matters

Iron-deficiency anaemia is a low haemoglobin caused by low iron stores. In premenopausal women, heavy menstrual periods are a common cause. In men, in postmenopausal women, and in younger women without heavy periods, the assumption is that the iron is being lost from somewhere in the gut — and the gut needs to be checked.

The reason is simple: bowel cancer can cause silent, low-level blood loss that produces no obvious bleeding but slowly drops your haemoglobin. Catching it through an anaemia workup can be life-saving.

The standard workup

After your GP confirms iron-deficiency anaemia on blood tests (low haemoglobin, low ferritin, low transferrin saturation), the standard specialist investigation is:

• A coeliac antibody test — coeliac disease causes iron deficiency and is easy to miss without testing.
• A gastroscopy — to look for ulcers, gastritis, cancer, vascular abnormalities, and to take small-bowel biopsies for coeliac.
• A colonoscopy — to look for polyps, cancer, inflammation, vascular abnormalities. Usually done in the same anaesthetic as the gastroscopy.

These two procedures together identify the cause in about 70–80% of cases.

If both are normal but anaemia continues

About 1 in 5 patients with iron-deficiency anaemia have a normal gastroscopy and colonoscopy. The next consideration is the small bowel — the six metres between the stomach and the large bowel that neither scope reaches.

Capsule endoscopy is the standard test for this. You swallow a vitamin-sized wireless camera that photographs the small bowel for eight hours. The specialist reviews the footage looking for ulcers, vascular lesions, tumours and signs of inflammation. See our capsule endoscopy page for details.

Other tests in selected situations

• CT enterography or MRI enterography — cross-sectional imaging of the small bowel, useful if Crohn’s disease is suspected.
• Double-balloon enteroscopy — a longer scope that can reach deeper into the small bowel, used for treating lesions found on capsule endoscopy.
• Tagged red cell scan or CT angiography — used for acute, brisk bleeding where the source isn’t obvious.
• Coeliac genetics — if coeliac antibody testing is equivocal or you’ve been on a gluten-free diet.

Treatment alongside investigation

While we investigate, your GP will typically start iron replacement — usually oral iron tablets, or if those don’t work or you don’t tolerate them, intravenous iron infusion. Treating the anaemia symptomatically is important, but it doesn’t replace finding and treating the cause.

Don’t accept iron infusion as the end of the story for unexplained iron deficiency. The infusion treats the number, not the leak.

When to refer urgently

Some features make iron-deficiency anaemia more concerning:

• Rapidly dropping haemoglobin.
• Severe anaemia
• Visible bleeding from anywhere.
• Weight loss, change in bowel habit, or family history of bowel cancer.
• Age over 50 with no obvious menstrual cause.

These warrant prompt specialist review rather than watch-and-wait.

About your specialist — Dr Goutham Sivasuthan

Dr Goutham Sivasuthan is an Australian-trained specialist surgeon, with conjoint accreditation by the Gastroenterological Society of Australia (GESA) in both upper GI endoscopy and colonoscopy. He completed his medical degree at the University of Queensland and his advanced training across Brisbane’s tertiary hospitals.

Dr Goutham consults and operates exclusively at Brisbane-region day-surgery and hospital facilities, and is the only clinician you’ll meet through your care — from your first consultation, through your procedure, to your follow-up. He is committed to no-gap care for insured patients and transparent pricing for everyone else.

Frequently asked questions

Can iron deficiency be caused by diet alone?

Pure dietary iron deficiency without GI blood loss is uncommon in adults eating a varied diet. It’s more common in vegetarians and vegans, and in pregnancy. But in general, dietary iron deficiency is a diagnosis of exclusion — we check the gut first and don’t blame diet without good evidence.

Will iron infusion fix me without further tests?

Iron infusion will top up your iron stores quickly, but if the cause is ongoing GI blood loss, the anaemia will come back. Investigations are about finding and treating the cause, not just refilling the tank.

How often do you find a cause?

Gastroscopy and colonoscopy together identify a cause in about 70–80% of patients. Capsule endoscopy picks up another 10–15%. A small minority have no source identified despite full investigation — these patients have ongoing surveillance.

Is it safe to delay investigation if I feel fine?

Iron deficiency can develop gradually and you may feel surprisingly normal until it’s quite severe. Delaying investigation risks missing a treatable cause. Once your GP has confirmed iron-deficiency anaemia, the investigation should follow within weeks rather than months.

Can I just take iron tablets and avoid the scopes?

If you have iron-deficiency anaemia and a known cause (heavy periods, coeliac on a strict diet), oral iron alone is reasonable. If the cause is unknown, taking iron without investigating can mask underlying disease — including, occasionally, an early bowel cancer that would have been curable if caught.

This article is part of our specialist series on bowel and gut health. For the full overview, see our main service page.