Anaemia occurs when you do not have enough healthy red blood cells to carry the oxygen you need around your body. If you have anaemia you may feel tired, light headed and weak.

On this page, you can find the following information:

What is anaemia?

The red blood cells in your blood contain an iron-rich protein called haemoglobin. The haemoglobin helps carry oxygen from the lungs to your body’s tissues. Anaemia is the result of your body not having enough healthy red blood cells to carry the oxygen you need around your body.

There are many different types of anaemia. 

What causes anaemia?

The three main causes of anaemia are:

  • losing too much blood
  • not making enough healthy red blood cells
  • the destruction of too many red blood cells.

Losing too much blood

This is a common cause of anaemia. Situations where too much blood can be lost include:

  • when women have heavy bleeding during their periods
  • stomach ulcers or other problems that cause bleeding inside the body
  • blood loss from surgery or an injury.

Not making enough red blood cells

Your body may not make enough red blood cells if your diet is lacking in nutrients (eg, iron, folic acid, vitamin B12, and vitamin C) or is not able to absorb these nutrients properly from the gut. 

  • The most common cause of anaemia is iron-deficiency from low iron intake or increased blood loss. 
  • Vitamin B12 or B9 (commonly called folate) deficiency. This causes the body to produce abnormally large red blood cells that cannot function properly.
  • Sometimes a long-term disease keeps your body from making enough red blood cells such as kidney disease, arthritis, diabetes or cancer.
  • Your body may not produce enough red blood cells during pregnancy when extra red blood cells are needed for the growing baby. 

Destroying too many red blood cells

Red blood cells last about 3–4 months in the body. In some situations, the red blood cells are damaged or destroyed more quickly than normal. Examples are when you have a disease such as sickle cell disease or thalassemia or have certain medical treatments, eg, chemotherapy.  

What are the symptoms of anaemia?

Some people with mild anaemia do not show any symptoms. The common symptoms that people show are:

  • feeling tired or having little energy (lethargy)
  • feeling faint and dizzy
  • looking pale, having pale skin
  • being short of breath or feeling breathless
  • headaches
  • faster heart rate or a thumping heart (palpitations)
  • cold hands or feet
  • lack of concentration.

See your doctor if you think you have anaemia.

As some serious conditions can cause anaemia, see your doctor urgently if you have any of the following:

  • weight loss, fevers, bone pain, and night sweats
  • unexplained changes in your bowel habits.

How is anaemia diagnosed?

Your doctor can help diagnose anaemia. They will ask you about your lifestyle and medical history. You may need regular blood tests, mainly a full blood count. This can measure how many red blood cells you have and how well they are working. The test can also check if you have enough vitamin B12 and folate in your body to help it make the red cells you need.

Depending on the type of anaemia you have, sometimes other tests may be needed to check for conditions that could be causing the anaemia.

What is the treatment for anaemia?

The treatment for anaemia depends on the cause and how severe your anaemia is. Treatment can include changing your diet and taking oral (by mouth) medicines. If your anaemia is severe, injectable medicines or a blood transfusion may be needed.

If your anaemia is due to another condition, treatment of the other condition may be needed to fix the anaemia.

Possible complications

If anaemia is left untreated, possible complications include an irregular heartbeat (called arrhythmias). Over time, arrhythmias can damage your heart and possibly lead to heart failure.

Anaemia can also damage other organs in your body because your blood can't get enough oxygen to them. If you have untreated iron-deficiency anaemia when you’re pregnant, your baby may be born prematurely. 

Learn more

The following links provide further information on anaemia. Be aware that websites from other countries may contain information that differs from Aotearoa New Zealand recommendations.

Anaemia  Healthinfo, NZ
Anaemia UCL Hospitals, UK
Vitamin B12 or folate deficiency anaemia NHS, UK
Iron deficiency anaemia NHS, UK


Anaemias and some other blood disorders NZF, NZ
Anaemia on full blood count – investigating beyond the pale BPAC, NZ, 2013
Haematology department protocols and guidelines – anaemia Canterbury DHB, NZ, 2019

Information for healthcare providers

Anaemias and some other blood disorders NZF, NZ
Chronic kidney disease – managing anaemia
 NICE Guidelines, UK
Anaemia on full blood count – investigating beyond the pale BPAC, NZ, 2013
Investigating iron deficiency anaemia BPAC, NZ, 2013
Daily iron supplementation for improving anaemia, iron status and health in menstruating women Cochrane Developmental, Psychosocial and Learning Problems Group, 2016
Erythropoietins – haemoglobin concentration KHA-CARI guideline, NHMRC, Australia, 2011
Intravenous iron SaferRX
Anaemia in old age – common presentations BMJ Learning, UK [requires registration]

Credits: Sandra Ponen, Pharmacist. Reviewed By: Dr J Bycroft. Health Navigator NZ