Iron deficiency

Deficiency and anaemia are not the same thing

Iron deficiency means the body’s iron stores are depleted. Iron deficiency anaemia is the later stage, when there is not enough iron to make adequate haemoglobin.

It is entirely possible to be iron deficient with a completely normal haemoglobin and a normal full blood count. Stores run down first and the blood count falls later, so a normal blood count does not rule iron deficiency out.

Symptoms, and their limits

Early on, people often notice tiredness, difficulty concentrating and low motivation. As it progresses towards anaemia, symptoms can include marked fatigue, breathlessness, a fast or irregular heartbeat, dizziness and pallor.

Two honest caveats. Many people have no symptoms at all. And fatigue is one of the least specific symptoms in medicine — it accompanies poor sleep, low mood, thyroid disease, sleep apnoea and a long list of other conditions. Feeling tired is a good reason to get tested; it is not a good reason to start iron without testing.

What ferritin measures, and why it misleads

Ferritin is the protein that stores iron, and blood ferritin usually reflects how much iron is in store. It is the single most useful test — but it has a well-known weakness.

Ferritin is also an acute phase reactant, which means it rises with inflammation: during an infection, after surgery, with autoimmune conditions, liver disease, obesity and chronic kidney disease. So it is possible to be genuinely iron deficient while the ferritin reads normal or even high. This is the most common reason iron deficiency is missed.

In Australia a ferritin below about 30 µg/L usually indicates iron deficiency in adults, but the exact figure depends on the laboratory, on sex and pregnancy, and on whether inflammation is present — reference intervals are not standardised nationally. Where inflammation is likely, a higher threshold is used and other tests become important. Transferrin saturation below 20 per cent, alongside a full blood count and often a CRP, helps resolve the picture when ferritin alone is equivocal.

Why the cause matters

This is the part most often skipped. Iron deficiency has four broad causes, and treating the iron without addressing the cause means it comes back.

• Blood loss — heavy menstrual bleeding is the most common cause in menstruating people; bleeding from the gastrointestinal tract is the most common cause in men and in women past menopause; frequent blood donation also contributes
• Malabsorption — coeliac disease, inflammatory bowel disease, previous gastric or bariatric surgery, and Helicobacter pylori infection
• Increased requirement — pregnancy, breastfeeding, infancy, childhood growth and adolescence
• Reduced intake — restricted, vegetarian or vegan diets without attention to iron sources

When the gut needs investigating

Whether gastroscopy and colonoscopy are needed depends on age, sex, menstrual status and symptoms. Men and women past menopause with newly diagnosed iron deficiency anaemia are usually referred for both, because bleeding from the gastrointestinal tract is the most likely explanation and some of those causes are serious.

Younger women with heavy periods and no bowel symptoms are often not referred initially — but should be if there are bowel symptoms, a significant family history, or if the deficiency returns after treatment. Recent Australian commentary argues for considering endoscopic examination more broadly in adults with iron deficiency, and the decision is an individual one.

Coeliac disease should be considered in everyone with unexplained iron deficiency. It affects more than one in 70 Australians and four out of five remain undiagnosed. One practical point matters enormously: coeliac testing only works while gluten is still being eaten. Anyone who has already gone gluten free needs to reintroduce it for several weeks before testing, so it is worth testing before changing the diet rather than after.

Heavy periods

Heavy menstrual bleeding affects around one in four people who menstruate, and prevalence rises with age — from about 18 per cent at 22 to around 32 per cent by 48. It is the leading cause of iron deficiency in this group and it is frequently normalised.

Practical markers of heavy bleeding: clots larger than a 50 cent coin, changing a pad or tampon every hour, needing to change overnight, flooding through clothing, or bleeding for more than eight days. Bleeding after menopause is never normal and should always be assessed.

Treatment

Diet alone rarely corrects an established deficiency, but it matters for maintenance. Haem iron from meat, poultry and fish is absorbed considerably better than non-haem iron from plants. Vitamin C improves absorption of non-haem iron; tea, coffee, wine, calcium and the phytates in wholegrains reduce it. Cooking helps — the body absorbs around 6 per cent of the iron from raw broccoli and around 30 per cent from cooked.

Oral iron supplements are the usual treatment. Absorption is better on an empty stomach, an hour before or two hours after food, taken with water or juice rather than tea, coffee or milk. Constipation, nausea and abdominal discomfort are common and often settle.

One change in the evidence is worth knowing. A single dose raises hepcidin, a hormone that blocks absorption of the next dose for about a day — so taking iron every second day results in roughly twice the absorption of a smaller daily dose, and often fewer side effects. Alternate-day dosing is now the preferred approach for many people.

Treatment continues for at least three months after the blood count has recovered, and often longer. Haemoglobin recovers well before the stores do, and stopping when the blood count normalises is the most common reason for relapse.

Where oral iron is not tolerated, not working, or the deficiency is severe, an iron infusion may be considered. It works quickly and is generally well tolerated, but it carries a small risk of persistent brown skin staining at the drip site, which is worth understanding beforehand.

Follow-up

Blood tests are usually repeated during and after treatment, and then periodically for around a year, to confirm both that the deficiency has corrected and that it is staying corrected. Iron deficiency that returns after adequate treatment is itself a reason to look harder for a cause.

When to seek help sooner

Do not wait for a routine appointment with black or bloody stools, vomiting blood, chest pain or severe breathlessness, fainting, or bleeding after menopause. These need urgent assessment.

It is also worth not self-treating with iron bought over the counter before being tested. Iron overload is a real condition, iron is dangerous in overdose particularly for children, and taking iron before testing can obscure the picture that would have identified the cause.