List of Partners vendors. More employers are requiring pre-employment drug tests and developing random drug-testing policies, and the abuse of prescription drugs is reaching epidemic levels in the U. The length of time drugs stay in the system has drawn more attention from employers and employees.
In addition, the window of time that drugs can be detected in chemical testing can be critical information for both law enforcement and defendants in court proceedings. But the size and shape of this window can vary significantly from person to person and drug to drug. An exact timetable for how long drugs remain detectable in urine, blood, and saliva tests is almost impossible to determine.
There are many factors that can affect how an individual's body processes or metabolizes drugs. Drug detection times can be affected by a person's metabolic rate, which can vary widely. Metabolic rates, in turn, can be affected by age and certain health conditions.
The higher the metabolic rate, the shorter the time a drug can be detected in the body. Hydration levels, body mass, and physical activity affect how long drugs will be detectable. If someone has built up a tolerance to a drug, it tends to metabolize more quickly. This means the length of time it can be detected in their system can become very short. Another key factor in drug detection time is the amount and frequency of the drug's use.
Very frequent drug use can cause concentrations in the system that can be detected for lengthy periods after last use. Even the acid-base balance in urine can affect detection times in urine tests.
The more acidic the urine, the shorter the detection time. Hair follicle drug tests are less likely to be affected by the above factors—and also less likely to be tampered with. These tests can detect drug use for up to 90 days.
The disadvantage of using hair tests is that drugs will not show up in the hair for seven to 10 days. Also, hair tests are currently more expensive than the standard urine, blood and saliva tests in both collection and processing costs.
Because there are so many different factors affecting the time that drugs can be visible in chemical tests, researchers have not been able to nail down an exact timetable for the detection of individual drugs using standard testing.
Cut-off levels also reduce the chance of a person testing positive after only passive exposure to a drug. Secondhand smoke is one example of passive exposure. These fail to indicate that a person has recently done drugs.
A false-negative result can occur if the urine is very diluted. Many factors affect the length of time that a test can detect a certain drug in the body. These factors include:. If a person uses a drug very frequently or heavily, a urine test will detect the drug for a longer period. For example, the detection times for marijuana can depend on how often a person uses it:.
This table shows how long a urine test can detect certain drugs after a person has taken them:. The test requires little preparation. Usually, a person just has to urinate into a plastic container. It is important to note that certain medicines and supplements can cause false-positive results that indicate illegal drug use. A medical professional or technician will carry out the urine drug screen. They may start by asking a person to:. The technician will then measure the temperature of the urine sample to ensure that it is suitable for testing.
They will then seal the sample in a plastic bag. Both the donor and the technician should keep an eye on the sample until it is sealed, to make sure that no one has tampered with it. Sometimes, the technician will accompany the person into the test room to make sure that they are giving the sample correctly. The technician should explain the reason for this supervision.
Urine drug screen results usually come back within a few days. Some results come back on the same day. Negative results may come back more quickly. A positive result may take longer, because ensuring the accuracy may require further testing. If a result is positive, a person will need to take a second test for confirmation. This will be a GC-MS test, which will provide more accurate results.
A urine drug screen can quickly and effectively detect the presence of illegal or prescription drugs in the body. Random urine sample collection A random urine sample collection may also be called a urine drug screen. How It Feels Blood test The blood sample is taken from a vein in your arm. Urine test It is not painful to collect a urine sample. Saliva test It is not painful to collect a saliva sample.
Risks Blood test There is very little chance of a problem from having a blood sample taken from a vein. You may get a small bruise at the site.
You can lower the chance of bruising by keeping pressure on the site for several minutes. In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. You can treat this by using a warm compress several times a day. Urine test Collecting a urine sample does not cause problems. Saliva test Collecting a saliva sample does not cause problems.
Results A toxicology test tox screen checks for drugs or other chemicals in your blood, urine, or saliva. Toxicology tests Normal: No unexpected drugs are found in the sample. Abnormal: Unexpected drugs are found in the sample.
Levels of prescription or non-prescription medicines found in the sample are: Below the effective therapeutic range, or Above the therapeutic range, or High enough that they may be toxic. High values High levels may be caused by a drug overdose, either by accident or on purpose. Low values Low levels of prescription or over-the-counter medicines may mean that you are not taking your medicine correctly. What Affects the Test You may not be able to have the test, or the results may not be helpful, if: You drink or eat some types of food such as a food that contains poppy seeds.
You have blood in your urine. There is too much time between taking the drug and collecting the sample. You don't give a large enough urine sample. What To Think About In general, urine tests are better than blood tests at finding drugs. Traces of a drug may remain in urine longer than in blood.
Urine tests often can detect drug use within the last 5 days. Saliva tests can detect drugs just as well as urine and blood tests do, and they are less invasive than blood tests. This means they don't require a needle stick. A saliva test can detect drugs used within the past day.
Tox screen results are not always accurate. Sometimes a test may not find drugs that have been taken false-negative result. Or a test may find drugs when they have not been taken false-positive result.
Trying to change test results by drinking large amounts of water or taking other substances can be dangerous. And it usually doesn't change the results. A test result that shows drug use can have serious outcomes, such as arrest or job loss. But the test result may not be accurate. So a positive result should always be confirmed by at least two different test methods. A standard tox screen can't detect inhalant abuse, when someone sniffs common household products to "get high.
Laboratory Tests and Diagnostic Procedures, 6th ed. Louis: Saunders. Manual of Laboratory and Diagnostic Tests, 8th ed.
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