To ensure accurate test results, we recommend you wait two weeks if you feel unwell before taking the test. This is because fighting an infection can affect your test results and make them different from your normal levels. Most blood tests won't be affected if you're taking antibiotics, but amoxicillin can sometimes cause falsely high glucose levels. To be on the safe side, we suggest waiting for 48 hours after your last dose of amoxicillin before taking the test, even though it usually leaves your body within 24 hours.