almost untraceable. Scientists in Germany also tackled this subject in 2005. Their subjects were given pills with 2.5mg of THC and 1.35mg of CBD. Six hours after taking the pills, the subjects were not showing any signs of CBD in their systems, while THC was still found in their samples over a day later. Still Worried? Here are some tips and tricks to help ease any concerns with impending drug tests: Topicals Using topical CBD products can relieve pain issues, but (more importantly) they do not enter the bloodstream. Don’t Take Too Much Ingesting more than 2,000mg of CBD in a day can affect drug screening if it’s taken in a relatively short period of time. THC-Free CBD Products While there are CBD products on the market claiming to not contain THC, the industry is not heavily regulated.