What to expect from a blood test for anaemia

A clinician cleans the skin, places a small needle in a vein, and collects one or more tubes of blood. You may feel a brief prick and a little pressure; bruising can occur afterwards. The laboratory can assess haemoglobin, the number and size of red blood cells, and other blood-cell features. Depending on the pattern, your clinician may request tests related to iron, vitamin levels, inflammation, kidney function or blood loss. A result showing anaemia does not by itself identify its cause.

Check whether you need to fast; many blood tests do not require it, but preparation depends on the tests ordered. Tell the clinician about medicines, supplements, pregnancy, heavy menstrual bleeding, dietary restrictions and previous fainting during blood collection. Drink water unless you have been told to restrict fluids. Press firmly on the puncture site afterwards. Do not start iron or another supplement solely from a result without discussing the likely cause and the correct dose.

Arrange prompt medical review for worsening breathlessness, chest discomfort, fainting, a racing heartbeat at rest, marked weakness or bleeding that does not settle. Seek urgent help for black or bloody stools, vomiting blood, heavy uncontrolled bleeding or sudden collapse. Ask when your result will be available and what symptoms should lead you to call before the planned follow-up.

Ask which measurements were abnormal, whether the pattern suggests iron loss or another cause, whether more tests are needed, and when treatment should be reviewed.