Always ask your surgeon for specific instructions regarding taking or withholding your usual prescription medications, over the counter medications, or supplements. Many medications and herbal preparations can have adverse effects or interactions with other medications involved in surgery. In my practice, I have my patients go off "blood thinners", medications which affect clotting up to 2 weeks before and 2 weeks after surgery. Aspirin is the most obvious, but there are many medications which contain aspirin and non-steroidal antiinflammatories (NSAIDS- like ibuprofen and motrin,advil). Many herbal preparations also can cause post-operative bleeding such as garlic, ginseng, and ginkgo biloba. Depending on your surgery, the medication and your doctors preference, this interval can be different.