Haemoglobin

Hemoglobin (Hb) is the iron-rich protein inside red blood cells that picks up oxygen in the lungs and delivers it to every tissue in the body. It is also what gives blood its red colour. A hemoglobin test measures how much of this protein is in a given volume of blood, and it is the single most important number used to diagnose anaemia.

When hemoglobin is low, the body gets less oxygen than it needs, which can cause tiredness, breathlessness, paleness, dizziness, headaches and a racing heart. Anaemia is extremely common in India, especially among women, adolescent girls, pregnant women and young children, and iron deficiency is the leading cause. When hemoglobin is high, the blood can become thicker, and doctors look for causes such as dehydration, smoking, living at high altitude, or conditions that make the bone marrow produce too many red cells.

Hemoglobin is measured as part of a complete blood count (CBC), but it can also be tested on its own as a quick, low-cost check. Results are reported in grams per decilitre (g/dL). A single reading is a starting point: your doctor will look at your red cell indices, such as MCV, along with symptoms to find out why the level is low or high.