A complete blood count (CBC) looks at the three kinds of cells in your blood. It is often the first test a doctor asks for: as part of a health check, when you feel unwell or tired, or during a fever. It needs no fasting.
Red cells and haemoglobin
Red cells carry oxygen around the body, and haemoglobin is the protein inside them that does the carrying. For adults it is usually around 13 to 17 g/dL for men and 12 to 15 g/dL for women.
- Low haemoglobin is anaemia. It can make you tired, breathless or pale. Iron deficiency is the most common cause in India, especially in women, which is why an iron test is often taken alongside.
- The report also lists measures such as MCV, which describe the size of your red cells and help your doctor find the cause.
White cells
White cells fight infection. A usual adult count is about 4,000 to 11,000 per microlitre.
- A high count often points to an infection or inflammation.
- A low count can come with some viral fevers, including dengue, and with certain medicines.
- The differential count breaks white cells into types, which helps tell a bacterial infection from a viral one or an allergy.
Platelets
Platelets help your blood clot. A usual count is about 1.5 to 4.5 lakh per microlitre. During dengue, platelets can fall over a few days, which is why doctors repeat the CBC.
Reading your own report
- Every result is printed beside the lab's own normal range. Compare against that range, not a number from the internet: ranges differ slightly between labs, and with age and sex.
- A value just outside the range is often not a concern on its own. Your doctor reads the results together, alongside how you feel.
- If something is flagged, show the report to your doctor rather than starting treatment yourself.
