In rare cases, simvastatin can cause a condition that results in the breakdown of skeletal muscle tissue. This condition can lead to kidney failure. Call your doctor at once if you have unexplained muscle pain or tenderness, muscle weakness, fever or flu symptoms, and dark colored urine.This medication can cause birth defects in an unborn baby. Do not use if you are pregnant. Use an effective form of birth control, and tell your doctor if you become pregnant during treatment.Do not take simvastatin if you have liver disease or if you are breast-feeding.Before taking simvastatin, tell your doctor if you have diabetes, underactive thyroid, kidney disease, a muscle disorder, or a blood disorder:Avoid eating foods that are high in fat or cholesterol. Simvastatin will not be as effective in lowering your cholesterol if you do not follow a cholesterol-lowering diet plan.Avoid drinking alcohol while taking simvastatin. Alcohol can raise triglyceride levels, and may also damage your liver while you are taking simvastatin.There are many other drugs that can interact with simvastatin. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.