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 are functioning. Common types of blood tests include complete blood count (CBC), blood chemistry tests, and blood glucose 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 specific substances, such as glucose, cholesterol, and hormones. Results can provide valuable information about a person's overall health.