MODEL RELEASED. Blood sampling. Pregnant woman having a blood sample taken from her arm by gloved hands holding a syringe. Inside the syringe is a vacutainer, a small test tube which sucks in the blood after the vein has been pierced. The woman has a tourniquet tied around her upper arm which traps blood in the arm, enlarging the vein and making it easier to pierce. Blood samples such as this can be tested to provide medical information on nutrition, hormone balance, or blood toxin levels. They can also be used in the diagnosis of disease.