Haemoglobin is a protein present in the red blood cells and it carries oxygen from the lungs to the rest of the body. Iron is the most essential element in haemoglobin to which oxygen is attached. A haemoglobin (Hb) test measures the levels of haemoglobin in the blood. If the haemoglobin level is abnormal, it may be a sign of blood disorder or a deficiency in the blood. .Test explainedA haemoglobin test is often performed to check for anaemia, a condition in which the body has fewer red blood cells (RBC) than normal or the amount of Hb in RBCs is lesser. If a person has anaemia, the cells don't get all the oxygen they need. The test is prescribed to assess:•\tSymptoms of anaemia including weakness, postural dizziness, pale skin,and cold hands and feet•\tFamily history of thalassemia (a blood disorder of low haemoglobin level),sickle cell anaemia (a group of disorders that cause breakdown of red blood cells and decrease number of healthy blood cells) or other inherited blood disorder•\tA diet low in iron and minerals•\tLong term (chronic) or short term (acute) infections•\tA History of end-stage renal disease, liver disease, heart failure or malignancy (presence of cancerous cells)•\tExcessive blood loss due to an injury or surgical procedure or other unknown reason•\tThrombotic episodes to see for polycythaemia (excessively increased RBCs)Performing the testA small sample of blood is taken from the vein of the arm, using a small needle and a small amount of blood is collected into a test tube. One may feel a little sting when the needle is inserted and ejected. This process usually takes less than five minutes. There is no need for any fasting or special preparation before performing this test.Interpreting the testThe haemoglobin test not only evaluates the amount of Hb but also helps in diagnosing different types of anaemia or polycythaemia and narrowing the diagnosis to a certain cause by looking at the values of different components of the Hb test. If any of the levels are abnormal, it does not necessarily indicate a medical problem requiring treatment. Diet, activity level, medications, a woman's menstrual cycle and other factors may affect the results. It is advised to talk to your physician to learn what your results mean.Advantages of the testIt is a simple and quick test. There are no disadvantages other than a single prick sting that goes away in a couple of minutes.Dr Shraddha Lumpatki (Deshmukh) is aconsultant physician and diabetologist.