Have drug testing questions? Get answers from Experts
This is Dr. Bonilla.
I understand your concerns. The threshold for cannabis is 50 ng. Depending of the use and frequency the test can be positive. For example: infrequent user the test will be positive up to 5 days after exposure. Frequent users after 15 days after cannabis was used. Please rate my answer. Let me know if you have any other questions.
The other expert has opted out.
After 13 days, the vast majority of marijuana smokers would be negative. Chronic heavy smokers can commonly remain positive for 30 days, and rarely even longer. But most people do not fall into this category, so most people would be negative for a test performed 13 days after last use.