Indications 

Synthroid (levothyroxine) is an orally administered prescription medication that is prescribed as a replacement therapy for congenital or acquired hypothyroidism affecting the thyroid, pituitary, or hypothalamus.  

This medication may be recommended for pituitary thyrotropin suppression and used as an adjunct to surgery and radioiodine therapy to manage thyrotropin-dependent well-differentiated thyroid cancer. 

It should be noted that Synthroid is not intended to suppress benign thyroid nodules and nontoxic diffuse goiter among iodine-sufficient patients. Furthermore, Synthroid is not indicated for the treatment of hypothyroidism during the recovery phase of subacute thyroiditis. 

Uses and Dosage 

Before taking levothyroxine, carefully read the Patient Information Leaflet provided by your pharmacist. If you have any questions regarding the medication, feel free to consult your doctor or pharmacist. 

Take this medicine orally as prescribed by your physician, typically once daily, preferably on an empty stomach, 30 minutes to 1 hour before breakfast. Unless directed otherwise by your doctor, swallow the tablet with a full glass of water. 

For infants or children who cannot swallow the tablet, crush it, and mix it with 1 to 2 teaspoons (5 to 10 milliliters) of water, and administer it using a spoon or dropper immediately. Do not prepare a supply in advance, and avoid mixing the tablet with soy infant formula. For more information, contact your pharmacist. 

The dose of this medication is determined based on various factors, including age, weight, medical condition, laboratory test results, response to treatment, and other medications you are taking. Make sure to inform your healthcare provider about all the products you are currently using, including prescription drugs, nonprescription drugs, and herbal products. 

To obtain the maximum benefits of this medicine, use it regularly at the same time each day. Do not stop taking this medication without first consulting with your physician, as thyroid replacement therapy is usually taken for life. 

Side Effects 

Allergic Reaction

Signs of an allergic reaction to Synthroid: 

• Hives 
• Difficult breathing 
• Swelling of face, lips, tongue, or throat 

Severe Side Effects

Contact your doctor immediately if you experience: 

• Fast or irregular heartbeats 
• Chest pain or pain that spreads to your jaw or shoulder 
• Shortness of breath 
• Fever, hot flashes, or sweating 
• Tremors or feeling unusually cold 
• Weakness, tiredness, or sleep problems 
• Memory problems or feeling depressed or irritable 
• Headache, leg cramps, or muscle aches 
• Nervousness or irritability 
• Dryness of skin or hair or hair loss 
• Irregular menstrual periods 
• Vomiting, diarrhea, appetite changes, or weight changes 

Common Side Effects 

• Chest pain or irregular heartbeats 
• Shortness of breath 
• Headache, leg cramps, muscle pain, or weakness 
• Tremors, feeling nervous or irritable, or trouble sleeping 
• Increased appetite 
• Feeling hot 
• Weight loss 
• Changes in menstrual periods 
• Diarrhea 
• Skin rash or partial hair loss 

Caution 

Do not administer this hormone if you have a known hypersensitivity to levothyroxine or any of its inactive ingredients. Exercise caution and remain observant for serious allergic reactions, such as skin rashes, facial swelling, swollen lymph nodes, difficulty breathing, or severe dizziness. In such cases, discontinue the use of this medication immediately and seek urgent medical attention. 

Individuals with a history of heart disease, thyrotoxicosis, adrenal gland dysfunction, hypertension, and diabetes may not be suitable candidates for this medication. Due to possible drug interactions, consult with your healthcare provider about all prescription and non-prescription medications, supplements, and herbal products you are taking.