I had taken levothyroxine for more than three years because of hypothyroidism. my doctor said i probably take this medicine for life. please let me know what is the side effects ?

Hypothyroidism : Sounds like the medication is needed for the rest of your life no matter what the side effects are. The medication can cause fragile bones. If the medication is not well adjusted it can cause sweating, tremor, diarrhea, constipation, weight gain or loss, anxiety.

For life: You do need to take this medication for life. You ought to follow your doctor's advice about monitoring the dose of the medication.

See below: Levothyroxine is a manufactured form of a naturally occurring chemical that is necessary for metabolism. Side effects may occur if the dose of the drug is too high, with symptoms that may include one or more of the following: racing heart, anxiety, hyperactivity, weight loss, irritability, diarrhea. If the dose is too low, symptoms may include: fatigue, constipation, and weight gain.