I think my daughter is using heroin. She had a urine test that is negative. But her creatine is very high. What did she do to cause this?

Please be specific in relation to "very high" creatinine. Second, most drug (opiate) tests easily detect heroin and likewise test for a ratio of creatinine and specific gravity in results. Had this been suspicious the test would have been "inconclusive" as opposed to "negative."