Rest before you test. Remember to sit and relax for at least 5 minutes before checking your blood pressure. Your blood pressure is often affected by your interaction with your environment or a temporary state of being. It might be elevated when you are experiencing stress, physically active, or having an extreme emotional response (very happy or very sad). It might be lower if you are very relaxed, dehydrated, or taking certain medication. To get an accurate blood pressure estimate, check it after resting for a few minutes and recheck it on a few different days.