Synthroid is a hormone. It is usually used for adding thyroid hormone to your body in the case of your organism hasn't ability to make it enough. This drug is also can be taken to prevent goiter. It's forbiden for using to avoid weight problems. It may also be useful for other health problems, which are not described here. If you have an allergy to Synthroid or to some components it consists of don't use it. If you have an allergy to some drugs related to Synthroid you should also avoid using of it. You should be careful in using it if you have a heart problems, anemia, diabetes, coronary artery disease or high rate of thyroid hormone in your organism. You should note that different brands of Synthroid work in different way. So it's recommended to have consultancy with your doctor before using it. You may use this medicine alone or in complex with others drugs. But it's strongly recommended to not use it with prescription and nonprescription drugs, dietary medicine, herbal drugs. You should also ask your doctor if this medicine could be compound with other drugs you are taking. You should have consultancy with your doctor before using Synthroid to prevent negative effects.