In some cases, blood toxicology testing may be used to screen candidates for a job that has high requirements and expectations. Police officers, safety workers, and people working with children must be in full control of their faculties, and cannot be under the influence of banned substances. Toxicology tests may also be used in various situations where a crime has been committed - this may be a simple case of driving while under the influence of drugs or alcohol, or it may be a case of date rape using a drug. Toxicology tests are also used to determine whether a person has collapsed due to a drug overdose, or whether the unusual symptoms that are being observed are the result of knowingly or unknowingly ingesting certain drugs and other chemicals. Toxicology testing is also used in sports to detect the use of performance enhancing drugs.
The main thing you need to do is inform your doctor about any drugs you may be on. These could be drugs that your doctor himself or herself has prescribed, they may have been prescribed by another doctor, or they may be over the counter drugs. Whatever the case may be, the tests results are highly likely to be affected by these drugs, and it is important that your doctor is aware of this.
A toxicology blood test typically follows a similar procedure to any other blood test. The doctor or nurse performing the procedure first ties an elastic band around your upper arm in order to restrict the flow of blood. This causes your veins to bulge, thus making it easier to insert the needle into a vein. Your forearm will then be cleansed with alcohol in order to prevent any infection, and the needle will then be inserted. Experienced doctors and nurses will usually manage to insert the needle correctly in the first try itself, but often several tries will be needed. After the required amount of blood is drawn, the band and syringe are removed while pressing a wad of cotton on the puncture wound, which will then be covered with a small bandage.