It is used to treat an underactive thyroid (hypothyroidism).

Thyroxine Tablets 50mcg 100's
Hair loss may occur during the first few months of treatment. This effect is usually temporary as your body adjusts to this medication. If this effect persists or worsens, tell your doctor or pharmacist promptly.
This therapy is contraindicated if the serum TSH level is already suppressed due to the risk of precipitating overt thyrotoxicosis
Before taking levothyroxine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: increased thyroid hormones (thyrotoxicosis), decreased adrenal gland function, heart disease(such as coronary artery disease, irregular heartbeat), high blood pressure, diabetes.
Children may be more sensitive to certain side effects of this drug, especially headache, visionchanges, and hip/leg pain. High thyroid hormone levels may lead to decreased bone development/growth and reduced full adult height. Keep all lab/medical appointments so the doctor can monitor treatment.
This medication should not be used for weight loss. Normal doses of this medication will not work for weight loss, and large doses of this medication may cause serious, possibly fatal side effects, especially when taken with diet pills.
There appears to be no risk when taking this drug during pregnancy.
Some products that may interact with this drug include: "blood thinners" (such as warfarin), digoxin, sucroferric oxyhydroxide