thyroid level became so very high for a just stopped taking. I am 53 and have been on levothyroxine since 8 yrs old. I am now 54 yrs. It took about 6 months to become so extremely high. I for 10 yrs now am constantly resetting the mcg for they cannot keep it stable . Currently now on 300mcg synthroid. Still having trouble regulating. Been to at least 6 different drs. Its like it works than flips on me. The side effects I am experiencing are brutal. I went to dr. again yesterday and now am at 188. and rising.