Many supplements contain active ingredients that have strong biological effects in the body. This could make them unsafe in some situations and hurt or complicate your health. For example, the following actions could lead to harmful – even life-threatening – consequences. -Combining supplements -Using supplements with medicines (whether prescription or over-the-counter) -Substituting supplements for prescription medicines -Taking too much of some supplements, such as vitamin A, vitamin D, or iron Some supplements can also have unwanted effects before, during, and after surgery. So, be sure to inform your healthcare provider, including your pharmacist about any supplements you are taking.