This question is rather challenging to answer with a concrete number since there are many factors that can influence how long a specific drug will test positive in someone's system. Cocaine tests measure a metabolite known as benzoylecgonine, which is a by-product of the metabolism of cocaine in the human body. This metabolite goes to the fat cells, and then is released as the body burns the fat cells for energy. The benzoylecgonine released in the urine reacts with the cocaine drug test, providing a positive reading.

Most individuals will test positive for cocaine use 2 to 4 days after using. However, different individuals may test positive for up to 14 days and in chronic heavy users some benzoylecgonine can be detected in the urine for up to 22 days. Individuals that use other prescription or illegal drugs may have different times for testing positive for cocaine or the other drug or substance. Most cocaine drug test kits test for levels of benzoylecgonine at 300 nanograms per milliliter, which is the standard recognized by the National Institute of Drug Abuse, Substance Abuse and Mental Health Services Administration as the baseline reading for positive. Can a cocaine drug test tell you how long ago the drug was consumed or in what form? It is important to know that cocaine may be ingested or used in many different forms and even combined with other illegal or prescription drugs. While a cocaine drug test will let you know if cocaine has been consumed in the last 24-48 hours through the presence of benzoylecgonine in the urine or saliva, there is no way to know how it was taken. Likewise the cocaine drug test cannot tell you exactly when the drug was used, but you can narrow down the timeframe somewhat. In order to show at the 300ng/ml rate on most tests the drug must have been consumed prior to 48 hours before the test. This may not be true for chronic users or for someone that used more than a typical dosage of cocaine regardless of how many times they had used in advance. Combining cocaine with other drugs may slightly change the timeframe but typically not significantly. Can a cocaine drug test give a false reading? Like any type of substance testing, approximately 98-99% of the time the test will be 100% accurate. In some rare cases, generally because of tester error, the test may be inaccurate. In these situations retesting at the next possible opportunity or using a saliva test instead of a urine test or vice versa can often verify the result or signal that a full lab test needs to be completed. Often the greatest cause of errors in reading a cocaine drug test occurs from waiting too long to read the test or reading the test too soon. It is essential that anyone using a cocaine drug test read and follow all the manufacturers instructions, including correctly timing the test prior to reading the results.