st. john's wort is an herbal supplement that has many drug interactions. in your case it can make your simvastatin less effective which can result in elevated cholesterol levels. it also can affect blood glucose. i would suggest you avoid st. john's wort. if you are having symptoms of depression (a common use for st. john's wort) you should talk to your health-care professional who can help.
can i take st. john's wort safely with metformin enalapril simvastatin hctz and omega-3 fish oil?