Interfering Factors 1. Stress and strenuous exercise will falsely elevate uric acid. 2. Many drugs cause increase or decrease of uric acid (see Appendix E). 3. Purine-rich diet (e.g., liver, kidney, sweetbreads) increases uric acid levels. 4. High levels of aspirin decrease uric acid levels. 5. Low purine intake, coffee, and tea decrease uric acid levels.