One of the most common misconceptions about herbs and supplements is the thought: "These are all natural, so I can take what I want and how much I want." This is definitely not the case. I have always told my patients, you can probably do more damage with herbs than you can with acupuncture. Herbs are a powerful medicine and it is important to always inform your provider what medications you are taking. One of the most common interactions is that of Chinese herbs affecting a patient taking blood thinners. Many herbs can enhance or inhibit the actions of these drugs.
More and more research is showing how supplements are interfering with cancer drugs and chemotherapy. As in the video link below, Shelly started loading up on "Immune Enhancing" supplements while undergoing cancer treatment. She was even taking up to 60 pills per day! This actually had a counter affect and made her white blood cell level drop, causing her to delay her chemotherapy treatments for weeks.
All in all, most herbs and supplements are safe to take. You should always tell your healthcare provider what prescription drugs as well as what herbs and supplements you are taking.