Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. The half life of the marijuana is around ten days and it will be cleared of from body in three weeks. In your case you had smoked only once and it might not be detected in blood or urine. Trace amount can not be detected by routine tests. As of now drink plenty of water to keep yourself hydrated. Hope You will clear the test. Wishing you good luck.