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How long does it take for Levothyroxine to kick in?
Hi everyone,

I was recently diagnosed and have been taking 100 mcg Levothyroxine for almost 5 weeks.  My initial test reflected a TSH level of 350; I went in for a blood test at the 4 week mark and my TSH was 12.  

My question is this: how long will it take for my medication to kick in and bring my TSH levels to a normal level and for the side effects of hypothyroidism to subside?  Should I be taking a higher dosage of Levothyroxine at this point?

I am going to see the doctor tomorrow to speak with him about the results; I live in the UK and am not sure if they test for FT3 levels but will ask.

Thanks in advance!

Sami
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Since T4 meds have a half life of about one week, it takes around 4-5 weeks to reflect most of the medication in your blood.  That is why many doctors wait for 2-3 months for a return visit and more testing.   Unfortunately many doctors in the US and most in the UK have the "Immaculate TSH Belief" and rely too heavily on TSH as a diagnostic for thyroid problems.  That doesn't really work because TSH is a pituitary hormone that is affected by so many variables that it really doesn't correlate with what is most important , which is symptoms.  Scientific studies have shown that the biologically active thyroid hormone free T3  correlates best with hypo symptoms, while TSH and FT4 did not correlate.  

In my opinion the best way to treat a hypo patient is to test and adjust levels of FT3 and FT4 with whatever meds are required to relieve symptoms, without being constrained by resultant TSH levels.  Symptom relief should be all important, not TSH level.  Many of lour members have reported that symptom relief for them required that FT3 was adjusted into the upper part of its range and FT4 adjusted to at least midpoint of its range.  If you doctor is unwilling to treat you clinically (for symptoms), in this manner, then you will ultimately have to find a good thyroid doctor that will do so.

So push hard for FT3 and FT4 tests (not total T3 and total T4), along with TSH.  I would also inquire if the doctor is going to be willing to treat you clinically, as outlined above.  Being in the UK complicates this whole process a lot, I know, but there have been members in the UK who have reported finding doctors that would do this.  

If you get that testing done, I suggest that you get a copy of the lab report and post the results and reference ranges shown on the lab report so that members can help interpret  and advise further.  
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Thanks gimel, you're a star.  I've been lurking on this board for a bit before registering and the answers that you have written have always been clear and helpful.  I am going to see my doctor today and will tell him word-for-word what you wrote.

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