Iron deficiency: blood tests, treatment and when to investigate

In adults, ferritin below about 30 micrograms/L usually indicates depleted iron stores. A result above this does not always exclude iron deficiency, particularly with inflammation. I interpret it alongside your blood count, symptoms, other results and previous tests.

Awanui Labs changed its lower ferritin reference limit to 30 micrograms/L for adults aged 20 and over in October 2026. A laboratory range helps interpret a result; it does not, by itself, decide whether you need treatment or endoscopy.

Heavy periods can account for iron loss and should be treated. Gastrointestinal tests may still be appropriate if anaemia is persistent or recurrent, seems greater than the menstrual loss would explain, or comes with concerning symptoms or a relevant family history.

Low ferritin with a normal haemoglobin does not automatically mean you need endoscopy. The decision depends on your symptoms, risk factors and whether iron levels improve and stay up.

Coeliac blood tests and a urine test may be part of the assessment. Keep eating gluten until coeliac testing is complete. H. pylori testing is useful in some situations, particularly if initial investigations have not found an explanation.

If colonoscopy is unsuitable, a CT colonography scan may be an alternative. It cannot take biopsies or remove polyps, so an abnormal result may still lead to colonoscopy.

If iron causes nausea, constipation or abdominal discomfort, tell your GP or pharmacist. A lower dose or taking iron every second day can be easier to tolerate. The amount of elemental iron matters more than the total weight printed on the packet.

Changing the formulation or taking it with a small amount of food may help. Some products, including Maltofer, are intended to be taken with food.

Vitamin C helps absorption of iron from food. Taking iron with vitamin-C-rich fruit or a drink is reasonable if it suits you, but an extra vitamin C supplement is not usually essential. Keep iron separate from tea, coffee, calcium and interacting medicines; your pharmacist can advise the timing.

If gastrointestinal side effects remain troublesome despite adjustments, or your blood results are not improving, an iron infusion may be appropriate. The choice depends on your results, how you tolerate tablets and any ongoing iron loss.

Iron commonly darkens bowel motions. Black, sticky or tar-like motions, especially if you feel unwell, should still be assessed. Keep iron out of children’s reach: an overdose can be dangerous.

NZ products and funding checked against the November 2026 Pharmac Schedule and product information. Your pharmacist can confirm availability, costs and the right dose for you.

Yes, if blood tests show that your iron stores are low. A normal haemoglobin does not rule out iron deficiency. Replacing iron can improve fatigue in some people, although it will not relieve every cause of tiredness. Oral iron is usually tried first, with repeat blood tests to check the response.

If your iron stores are normal, taking extra iron is unlikely to help and can be harmful. Persistent tiredness may need assessment for other causes. Low iron with a normal haemoglobin does not automatically require an infusion or endoscopy; these decisions depend on your symptoms, results and circumstances.

The team monitors you during and after treatment. Tell the nurse straight away if the drip site hurts or burns, or you feel unwell. Leakage around the needle can stain the skin. Serious allergic reactions are rare.

Some preparations, particularly ferric carboxymaltose (Ferinject), can lower blood phosphate. A blood test may be needed if you have risk factors or repeated infusions. Report new or worsening muscle weakness, unusual tiredness or bone pain afterwards.

Useful sources include meat, fish, poultry, lentils, beans, tofu and iron-fortified cereals. Vitamin C foods, such as kiwifruit, citrus fruit or capsicum, help with absorption of plant-based iron. Keep tea and coffee away from iron-rich meals where possible.

Most multivitamins contain too little iron to treat iron deficiency anaemia. Your GP or pharmacist can help you choose a suitable preparation.

With iron tablets, replacing depleted stores usually takes several months. Treatment often continues for about three months after haemoglobin returns to normal. It can take longer if bleeding continues, absorption is reduced or side effects limit how much iron you can take.

An infusion supplies iron more quickly, but your body still needs several weeks to make new red blood cells. The dose and number of infusions depend on how much iron you need. Blood tests are usually repeated around six to twelve weeks afterwards to check the response and whether more treatment is needed.

Testing ferritin too soon after an infusion can give a misleadingly high result. Your team will tell you when to repeat tests and whether to continue or restart oral iron.

You swallow a small capsule camera. It takes pictures as it travels naturally through the small bowel and sends them to a recorder. It can show areas beyond the reach of standard gastroscopy or colonoscopy.

The capsule passes out in the bowel motions. It takes pictures but cannot take biopsies or treat bleeding. If bowel narrowing is a concern, another test may be needed first.