Proteins, nucleic acids are best example of natural polymers. Similarly cellulose is also a natural polymer which acts as main structural component of plants. Usually natural polymers are composed by condensation polymerisation with the elimination of water molecule.
Drug-Laboratory Test Interactions. False-positive urine immunoassay screening tests for phencyclidine (PCP) and amphetamine have been reported in patients taking venlafaxine. This is due to lack of specificity of the screening tests. False positive test results may be expected for several days following discontinuation of venlafaxine therapy. Confirmatory tests, such as GC/MS will clear that misconception up asap...or if you are not using pcp and your dr is sceptical.
This is very unusual for any one to have blood in the urine. Menstruation can cause a positive urine test. If you are not menstruating, then it means there is a source of bleeding within your bladder or ureter or kidney. This requires verification with additional urinalyses and then follow up testing if still positive. In brief: Blood in urine.