Before you start taking Lethyrox 100 Tablet, your doctor will do a blood test to see what dose you need. Once you start taking the medicine, you will have regular blood tests to see how well it is working, and the dose may be adjusted from time to time. It is best taken on an empty stomach before your first meal of the day. You should take this medicine regularly to get the maximum benefit. It may take several weeks before your symptoms start to improve. You may need to take it for the rest of your life. If you stop taking it, your symptoms are likely to come back.

The most common side effects of this medicine are caused by taking a bigger dose than you need. Possible side effects include palpitations (irregular heartbeat), vomiting, anxiety, diarrhea, weight loss, nervousness, or restlessness. Most side effects will disappear once you are on the right dose. Some people may suffer a severe reaction to high levels of thyroid hormone. Call your doctor straight away if you have a very high temperature, fast or irregular heart rate, low blood pressure, yellowness in eye/skin, confusion, or fits.

Lethyrox 100 Tablet may cause weight loss but should not be prescribed or taken to treat obesity. If you become pregnant while taking this medicine, inform your doctor right away as the dose may have to be increased/readjusted. Many other drugs affect the way this medicine works. Ask your doctor for advice if you are taking any other medications.