A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick. Learn how to perform, interpret and make simple lifestyle changes to improve the following blood tests for improved health; lactate (to detect and measure the severity of low levels of oxygen in the body (hypoxia) and also lactic acidosis), cholesterol (assess your risk of developing heart disease or stroke), glucose (concentration of glucose in the blood), and triglycerides (risk of heart disease and may be a sign of metabolic syndrome).