Do not use Synthroid if:

• you are allergic to any ingredient in Synthroid;
• you have a history of heart attack, chest pain (angina), adrenal gland problems, or elevated thyroid hormone levels that have not been treated.

• Synthroid may rapidly swell and disintegrate resulting in choking, gagging, the tablet getting stuck in your throat, or difficulty swallowing. It is very important that you take the tablet with a full glass of water. Most of these problems disappeared when levothyroxine tablets were taken with water.
• Tell your doctor or dentist that you take Synthroid before you receive any medical or dental care, emergency care, or surgery.
• If you are taking blood thinners at the same time as Synthroid, lab tests will be required to adjust the blood thinners.
• Diabetes patients - Synthroid may affect your blood sugar. Check blood sugar levels closely. Ask your doctor before you change the dose of your diabetes medicine.
• Lab tests will be required to monitor therapy. Be sure to keep appointments.
• Synthroid should be used with caution in children; overuse may reduce the child's final adult height.
• Pregnancy and breast-feeding: It is not known if Synthroid can cause harm to the fetus. If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using Synthroid while you are pregnant. Synthroid is found in breast milk. If you are or will be breast-feeding while you use Synthroid, check with your doctor. Discuss any possible risks to your baby.

Check with your doctor if any of these most common side effects persist or become bothersome:

• anxiety; diarrhea; flushing; mood swings; muscle weakness; partial, temporary hair loss; sleeplessness; stomach cramps; tiredness; vomiting.

• severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); changes in appetite; changes in menstrual periods; chest pain; difficulty breathing; excessive sweating; fast heartbeat; fever; headache; hives or skin rash; hyperactivity; inability to handle warm or hot room/weather conditions; irregular heartbeat; irritability; leg cramps; nervousness; pounding in the chest; seizures; shortness of breath; tremors; weight gain or weight loss.

Synthroid is to be used only by the patient for whom it is prescribed. Do not share it with other people.
If your symptoms do not improve or if they become worse, check with your doctor.