Thyroid UK
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Increase in Levothyroxine from 125 to 150 mcg

Hi, sorry to asking a question like so many others but I've been on 125 mcg for years and suddenly my requirements have gone up for no known reason. I tried to ask for figures but the most I could get from my doctor (telephone only these days unfortunately) is my TSH was 5.9 when normal is between 3 and 4.5. This doesn't seem to tie in with figures I've seen mentioned on this site. T4 was normal and no free T3 was done.

5 Replies

Sometimes our requirement for thyroxine does fluctuate. It is quite reasonable to assume you might need a small increase.

The normal range is usually around 0.3 to 4.5 or something similar so perhaps they meant 0.3 rather than 3.

Remember to make sure you are taking your thyroxine on an empty stomach with water only. You need to avoid taking certain other medications (such as antacids, PPIs, oestrogen containing pill etc) and supplements (particular calcium, magnesium and iron) at the same time. It is best to take your thyroxine an hour before or 4 hours after these other tablets. Absorption can be affected and this can play a big part in changes in your blood levels of thyroxine.

Sometimes some people find different brands of thyroxine are more effective than others, perhaps due to different absorption rates due to the different fillers used in them. This might also be contributing.

If your oestrogen levels have increased for any reason, this can cause and increase in the protein that binds to thyroxine which means you would have less thyroxine free and unbound in the blood. Common reasons for an increase in oestrogen are pregnancy, the contraceptive pill or HRT. Obviously these dont apply to men.

I hope that helps

Carolyn x


Thanks Carolyn - that is helpful. In a separate conversation with my doctor I had asked about why my hot flushes might have returned after ten years (I'm 70) and she said that losing weight (one and a half stone) would have released oestrogen into my blood stream. However, Zoe Harcombe (obesity researcher and diet guru) said she thought that was unlikely and other mature ladies who had lost weight agreed.


That is interesting. Did you lose the weight quite quickly? If so, that might explain why you may have been affected but others weren't.

I had read that losing weight releases oestrogen but I don't know much about it. I might see what I can find out :)


Yes, pretty much. Zoe Harcombe's diet club practice low carb and full fat (not high fat). You do tend to lose weight very rapidly for the first few weeks. But all the ladies are the same. I actually lost 6 lb while sitting in a chair with a broken leg (not that I'd recommend braking your leg of course :-) )


And congratulations on the weight loss :)

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