Can riboflavin cause a false positive for THC?

Yes, Riboflavin contains vitamin B2, as well as hempseed oil, both of which can create false positives, sometimes as high as 650 ng/mL (the cutoff level for most EMIT tests is 50 ng/mL). Furthermore, ibuprofen and Naproxen are known for causing the same false positives on these tests as well.