Home › Services › Iron deficiency
Condition
Iron deficiency anaemia and the gut
Low iron is usually treated with tablets or an infusion, and that is the right thing to do. The more important question is why it happened, and in a good proportion of people the answer lies in the gut. A/Prof Kariyawasam investigates iron deficiency in Sydney, often with a gastroscopy and colonoscopy on the same day.
Why the gut is investigated
The body loses very little iron on its own, so iron deficiency means one of three things: not enough iron in the diet, iron not being absorbed or iron being lost through bleeding. Diet alone is an uncommon cause in Australia. The gut is involved in the other two.
Coeliac disease is one of the causes most often missed here, because it can present as iron deficiency with no bowel symptoms at all, and the blood test for it is simple.
- Absorption: coeliac disease is the classic cause and sometimes the only sign of it. Previous stomach surgery, atrophic gastritis, Helicobacter pylori infection and long-term acid suppression can also reduce absorption.
- Slow bleeding that is invisible in the stool: from the stomach or duodenum (ulcers, erosions, some medicines such as anti-inflammatories and blood thinners), from the colon (polyps, bowel cancer, inflammatory bowel disease, abnormal blood vessels) and occasionally from the small bowel.
Right-sided bowel cancers and the flat serrated polyps that can precede them often bleed slowly and cause no other symptoms, so iron deficiency may be the only clue. Research from A/Prof Kariyawasam's group has found these lesions increasingly in younger patients.
Who needs investigation
Unexplained iron deficiency anaemia in a man of any age, or in a woman after menopause, is usually investigated with both a gastroscopy and a colonoscopy, normally in the same sitting, along with a blood test for coeliac disease.
The assessment also covers the everyday causes. These include diet, such as a vegetarian or vegan diet or eating little red meat, and regular blood donation, which steadily draws down iron stores. These can explain or add to low iron, but in a man or a woman after menopause they are not a reason to skip the gastroscopy and colonoscopy.
Younger women: periods are common, but not an automatic answer
Heavy periods are a frequent cause of iron deficiency and often the right explanation. But assuming it without asking the question has delayed diagnoses of coeliac disease, inflammatory bowel disease and bowel cancer in young women. Iron deficiency that is out of proportion to period loss, comes back despite treatment or comes with gut symptoms, weight loss or a family history, deserves the gut to be looked at.
Iron deficiency without anaemia, where iron stores are low but the blood count is still normal, is assessed on the same principles.
What the tests look for
At gastroscopy, biopsies are taken from the duodenum to look for coeliac disease even when it looks normal, and from the stomach where Helicobacter or gastritis is suspected. At colonoscopy, the whole colon is examined carefully, with particular attention to the right side, where the lesions that bleed slowly and silently tend to sit.
If both are normal and iron keeps falling, the small bowel is examined with a capsule endoscopy, a pill-sized camera that is swallowed and records pictures as it passes through.
Treating the iron deficiency
Iron is replaced at the same time as the cause is found. Tablets taken once a day, or on alternate days, are absorbed better than more frequent doses and cause fewer side effects. An iron infusion is used when tablets are not tolerated or not absorbed, when iron is needed quickly or in conditions such as inflammatory bowel disease.
Iron tablets are usually stopped about a week before a colonoscopy, because they darken the stools, which makes the lining harder to see.
Replacing iron without finding the cause fixes the blood test and can hide the problem, which is why the investigation matters as much as the treatment.
Where iron deficiency is investigated in Sydney
A/Prof Viraj Kariyawasam is a consultant gastroenterologist and hepatologist. Iron deficiency that needs a gut cause excluded is assessed at consultation in Norwest, Rouse Hill, Pennant Hills and Macquarie Park.
The gastroscopy and colonoscopy are performed at Norwest Private Hospital, Macquarie University Hospital and Pennant Hills Day Surgery. A referral from your GP is needed for a consultation.
Related pages
Common questions
The questions people actually ask, answered plainly.
Why do I need a colonoscopy for low iron?
Because slow, invisible bleeding from the bowel is one of the commonest causes of iron deficiency in men and in women after menopause, and some of those causes, including polyps and early bowel cancer, are only found by looking. A gastroscopy is usually done at the same time to check the stomach and to take biopsies for coeliac disease.
Can't I just take iron tablets?
Taking iron is the right treatment for the deficiency, but it does not explain why it happened. If the cause is bleeding from the gut, replacing iron can improve the blood test while the underlying problem continues.
I am a young woman with heavy periods. Do I need investigation?
Often not, if the iron deficiency fits with your periods and corrects with treatment. It is worth investigating if it is more than the periods would explain, keeps coming back or comes with gut symptoms, weight loss or a relevant family history. Coeliac disease should be checked with a blood test in any case.
What is an iron infusion, and do I need one?
An infusion gives a full dose of iron through a drip over a short time. It is used when tablets cause side effects, are not absorbed or do not work fast enough, and in some conditions such as inflammatory bowel disease. Your doctor will advise whether it suits you.
What if the gastroscopy and colonoscopy are normal?
If iron keeps falling, the small bowel is looked at next, usually with a capsule endoscopy. Blood loss elsewhere, including heavy periods and blood donation, and absorption problems are also reconsidered.
What is the best way to take iron tablets?
Iron is absorbed best on an empty stomach. Taking vitamin C with it was standard advice for years, but a randomised trial of 440 adults found it made no difference to recovery, so it is optional. Avoid tea, coffee, calcium-rich foods and antacids around the same time. If tablets upset your stomach, taking them with food or every second day is reasonable, and a dose every second day may be absorbed just as well. Your pharmacist can advise on timing with other medicines.
How long do iron tablets take to work?
Many people feel better within a couple of weeks, but blood levels take longer to recover and refilling the iron stores takes months. Tablets are usually continued for about three months after the haemoglobin returns to normal. If levels do not rise as expected, the iron may not be absorbed or blood loss may be continuing, and that needs looking into.
Is it normal for iron tablets to turn my stools black?
Yes. Dark or black stools are expected with iron tablets and are harmless. Constipation, nausea and stomach upset are also common, and taking iron with food or at a lower dose can help. Bleeding from the stomach can also cause black stools, so if you feel faint, dizzy or vomit blood, see a doctor the same day.
Do I need to stop iron tablets before a colonoscopy?
Usually, yes. Iron is normally stopped about a week before a colonoscopy, because it darkens the stools, which makes the bowel lining harder to see. Follow the written instructions from the rooms and ask when to restart.
My ferritin is low but my haemoglobin is normal. Do I still need tests?
Often, yes. Low iron stores without anaemia can have the same causes as iron deficiency anaemia, including slow bleeding from the gut or coeliac disease, only found earlier. An Australian review recommends that gastroscopy and colonoscopy be considered for all adults with unexplained iron deficiency, not only those who are anaemic. Whether you need them depends on age, periods, diet, blood donation and symptoms.
What are the side effects of an iron infusion?
Most people have none or only mild ones, such as headache, nausea or aching muscles and joints that settle within a few days. Serious allergic reactions are rare. Occasionally iron leaks into the skin around the drip and leaves a brown stain that can be long-lasting. Some infusions can lower phosphate levels in the weeks afterwards, which can cause weakness or tiredness.
Where these figures come from
- Gastroenterological Society of Australia, iron deficiency clinical update
- healthdirect, iron deficiency
- Coeliac Australia
- healthdirect, iron infusion
- Medical Journal of Australia, iron deficiency in the era of routine ferritin testing (2024)
This page is general information. It is not advice about your own situation, and it is not a substitute for seeing a doctor. If you have symptoms, see your GP.
Make an appointment
Appointments are booked through the rooms directly. Have your GP referral ready when you call or ask your GP to send it ahead. Urgent inflammatory bowel disease, rectal bleeding and positive bowel screening referrals are prioritised.
Norwest & Rouse Hill (02) 8530 1800 Pennant Hills (02) 9875 2311 Macquarie Park (02) 9812 3880