Hello from JustAnswer.
The Ritalin will typically not cause a false positive urine drug test result. Since the Ritalin acts similar to amphetamines
, there has been concern that it could cause a false positive result for amphetamines, but in clinical studies, this is not a real concern.
However, even if there is a false positive urine drug screen, the confirmatory test would be able to clearly determine that it is only Ritalin that is present and no amphetamine.
Lasix may help someone that has a low level of marijuana. Any intervention that increases urine flow, such as drinking extra water or using Lasix, will cause the urine to be more dilute and the concentration of any drug will be less. For many people, the level is such that diluting the urine will not make a difference, but for someone with a level that is otherwise only slightly above the threshold of detection, a decrease in concentration can make the result negative.
However, it is also possible to overdo interventions to dilute the urine, and any urine that is excessively dilute will raise a red flag on its own. So, using a modest increased fluid intake or a small amount of Lasix may be helpful, but too much could also be a problem.
If I can provide any clarification, please let me know.