A blood test is a medical procedure that involves taking a sample of blood to analyze it for various health indicators. This test can help diagnose conditions, monitor health, and assess how well organs like the liver and kidneys are functioning. Common types of blood tests include complete blood count (CBC) and blood chemistry tests. During a blood test, a healthcare professional typically uses a needle to draw blood from a vein, usually in the arm. The sample is then sent to a laboratory, where it is examined for factors such as glucose levels, cholesterol, and the presence of infections or diseases. Results are usually available within a few days.