Thyroid UK
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How long?

Does anyone know how long it takes for an increased dose of thyroxine to kick in?

I've been on thyroxine for around 13 years and have been taking 175mcg for almost 10 years. This has been upped to 200mcg a week ago due to TSH of 5.5. I'm feeling completely rubbish - exhausted, in pain, dizzy spells and really low. Had to take time off work today as just physically couldn't bring myself to go. I've also been diagnosed with polycystic ovaries in the past week.

From reading posts on here seems I should have been on an increased dose for a while - my annual check in August TSH was 3.5.

10 Replies

Cardiff_shell It takes about 6 weeks for the full effects of a dose increase to be felt.

On a dose of 175mcg it's very unusual to see such a high TSH. What about FT4 (and FT3 but it's rarely done). And what are the reference ranges? Are you above the range for TSH or at the higher end?

For thyroid hormone to work properly, vitamins and minerals need to be at optimal levels (not just in range). If you've had the following tested please post the results (with ranges), if not ask your GP to do them other the done privately:

Vit D






Welcome to our forum.

You sound under medicated as a TSH of 5.5 is too high when the goal of Levothyroxine is to restore the patient to euthyroid status which means for most people a TSH just above or below 1.0.

Sex hormone imbalances often cause others to be imbalanced, causing their own symptoms but also affecting good thyroid function. The ovaries and uterus need proper amounts of thyroid hormone as much as any other organ or system to function properly.

PCOS and menstrual irregularity are common in people with low thyroid hormone issues.

If you post recent blood test results complete with ranges (numbers in brackets) members will comment.


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Thanks for the responses.

Afraid I don't know any of the other results (TSH range I was told is <4.4). I was told my iron stores are very healthy though if that helps?

Yes specialist made link between PCOS and the thyroid. I've been bleeding non-stop since October then 2 weeks ago I had a few days of passing clots size of golf balls which is what kicked off the blood tests, ultrasound and seeing gynae. I'm having follow up blood tests and another ultrasound in 8 weeks.

As I've been consistently on the same dose for so long with no problems I've not really paid much attention to the do's and don'ts. How important is to avoid the foods recommended? For example, I started drinking quite a bit of soy milk about 6 months ago (never had it before), could that have caused the sudden change? Also as part of a health kick in the new year I've been eating lots of veg including sprouts and broccoli, again could this have caused the sudden change?


Cardiff_shell We Hypos should avoid all forms of soy unless it is fermented, so no soy milk, soy yogurt, soy 'meat' etc.

You are legally entitled to a copy of your results under the Data Protection Act so ask your surgery for a print out, post the results with their reference ranges as a start.


I've been having soy yogurts recently too. Damn Tesco for their offers... :)

Will do, thanks

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Yogurt is fermented.


Well, most supermarket yogurts have probably never seen a bacterium and contain a thickener to make them appear to be real yogurt - and they are pasteurised so any bacteria they did contain would be dead. So I doubt most of them really qualify as fermented food.

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"Natural", "live" yogurt will "yog" milk at home. I don't eat or buy the crap you've written about.

I may have been the first person in the UK to make soy yogurt, but the manufacturer didn't follow it up because, due to the starter culture, it couldn't be claimed to be vegan, like the rest of their products.


The sprouts and broccoli won't have affected you, but the soy milk will have. However, once you stop drinking it, if that was the only problem, things should go back to normal. But, there might be other causes, too.


Mostly only TSH is tested which is why many use private testing services.


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