Legal analysis: the hair can only be detected after stopping taking medicine for more than half a year and cutting off and growing new hair. Because people have the function of detoxification, everything they eat and breathe in every day contains a certain amount of toxins. For example, the therapeutic drugs used are toxic. After the drug is absorbed by the human body, the drug in muscle tissue is excreted through the kidney with water, and the drug in blood is excreted through the liver. No toxins are allowed to stay in the body. After stopping the drug, the toxins absorbed in the body will gradually be excreted. When the absorbed toxin is completely excreted from the body, the hair has been growing. During the growth process, the absorbed toxins will remain in a part of the hair, and there will be no residual toxins in the newly grown hair.

Legal basis: Article 15 of the Provisions on Drug Abuse Testing Procedures shall issue a test report within three days after receiving the test sample, which shall be signed by the tester and stamped with the special identification seal, and then sent to the public security organ entrusting the laboratory for re-inspection. After receiving the test report, the public security organ shall inform the tested person of the test results within 24 hours.