Thyroid UK
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Increasing levothyroxine for an op

Hi, I'm new here. I am diabetic and on metformin and have also been on levothyroxine 100mmg daily. I was booked in for a knee replacement for this coming Thursday BUT when the checked my blood my TSH was 7.4 . In December it was 3.4 . They have postponed my op until my level has reduced. I saw my doctor who was very unhappy to increase my medication but has done so as they wont go ahead with op if not. Is it dangerous to go up in medication. . Would I be able to have it reduced again after the operation ? Will this affect my blood sugars at all?

Thank you for reading this and thank you in advance for your advice.


6 Replies

Welcome to the forum, Piff.

You were under medicated to have TSH 7.4. If your GP was unhappy to increase dose you should dump him/her fast and get a GP who knows how your thyroid should be treated. The goal of Levothyroxine is to restore the patient to euthyroid status. For most patients that will be when TSH is 1.0 or lower with FT4 in the upper range. FT4 needs to be in the upper range in order that sufficient T3 is converted. Read Treatment Options in Email if you would like a copy of the Pulse article to show your GP.

You should have a thyroid test in 6-8 weeks in case a further dose increase is required.

Why would you want dose reduced after your operation?

Increasing Levothyroxine can increase blood sugar level and adjusting Metformin can reduce Levothyroxine absorption so it is a good idea to have TSH tested when Metformin is adjusted and blood sugar tested after Levothyroxine is adjusted.


Thank you for all this advice . my doctor was saying that they don't usually prescribe levothyroxine until there is a TSH of 10! ( a previous dr prescribed mine earlier)

The hospital are doing a test in 2 weeks which seems a bit soon to me. .

How do you find a dr that understands the thyroid?


If your doc is saying they want your tsh to reach 10 *on meds* (am I understanding that correctly?) they do not understand the basic principles of thyroid treatment.

On treatment you want your tsh to be low, even lower than a 'normal' person w a normal thyroid, near to 1 if not below.

How, why, when, where and who is not important once you're on meds, so if your other doc prescribed before your tsh reached 10 that is of no consequence now. Your current doc does not sound very clued up and in fact seems to be misunderstanding some basic building blocks of thyroid wellness.

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Thank you



It can be like looking for a needle in a haystack.

The fact that the anaesthesiologist won't operate while your TSH is 7.4 should tell your GP that his treatment protocol is wrong.

I would ask other GPs at your practice whether they will prescribe when TSH is <10 and, if not, change GP surgery. You can write to the practice managers of GP practices in your area and ask the question before moving.

Two weeks may be long enough to bring down TSH to a level acceptable to the anaesthesiologist or may indicate that it has reduced sufficiently to assume it will be okay by the time they want to operate.

1 like

Thank you


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