Prepare for your PSA Blood Test by following these instructions. Avoid vigorous exercise or ejaculation for 48 hours beforehand – both can raise your PSA level. Wait at least six weeks before taking this test if you've had a urine infection or urological intervention (e.g. prostate biopsy or cystoscopy). Do not take biotin supplements for two days before this test, discuss this with your doctor if it is prescribed. Please let us know in the supporting information if you take finasteride, dutasteride, or saw palmetto, as these can all affect your results.