It’s worth speaking to your doctor, as well as a dietitian or nutritionist before making any significant changes to your diet - especially if you have any underlying health condition or are pregnant, planning a pregnancy, or breastfeeding. So that your levels of certain nutrients can be monitored, your GP may want to run blood tests (among others) to establish your ‘baseline’. A dietitian or nutritionist can work with you to ensure you get sufficient nutrients that can be harder to obtain on a vegetarian diet.