Thyroid UK
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Underactive Thyroid

I was diagnosed with an underactive thyroid about 3 years ago. Stupidly I never took the diagnosis as seriously as it appears I should have... I have gone for quite a few month maybe even a year with not taking the tablets every day as described, sometimes not taking them for weeks at a time,

I have today been re prescribed with a 75mg dose of Levothyroxine after going to the doctor to complain about restless sleep, lack of bowel movement (sorry tmi) and that despite eating extremely healthy and attending the gym 3x a week I am not able to lose weight - I didn't realise all these are linked to the thyroid as well as my low mood.

Feeling so annoyed with myself and just wondering if anyone had any advice on how long if will take before I start see any difference in any of the above?

Thanks in advance :-) x

7 Replies

Don't worry, we all make these mistakes. I knew I was gluten intolerant for 30 years but I loved my home made bread, and ignored all the evidence I had Candida for 20!

It can take a long time to see changes with levothyroxine - anything from 2 weeks to six months(with 4-6 weeks being the most common, probably). Go back to your doctor after 6-8 weeks for another blood test.

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Are thyroids and coeliacs related? My Mam has an overactive thyroid and has had the gland removed from her neck. She was diagnosed with coeliacs 22 years ago. I have cramps etc with certain things like white bread & pasta so I avoid them as much as possible (I have been tested 2x for coeliac disease but the results have always been negative)

I'm hoping for the 4-6 weeks to notice a different.... stupidly looking forward to getting up tomorrow to take my first new prescription of 75mg 🙈 I just want to feel normal and 'me' again.


They often occur together, because autoimmune diseases hunt in packs.

I also tested negative for coeliac, but am definitely gluten sensitive. The blood test can throw up false negatives, but only very rarely.


Bullies eh! 😂 I have been tested both ways, with bloods and having an endoscopy as well x



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

For maximum absorption Levothyroxine should be taken with water 1 hour before or 2 hours after food and drink, 2 hours away from other medication and supplements, and 4 hours away from calcium, iron, vitamin D supplements and oestrogen.

It takes 7-10 days for Levothyroxine to be absorbed before it starts working and it will take up to six weeks to feel the full impact of the dose. Symptoms can lag several months behind good biochemistry.

You should have a follow up thyroid test 6-8 weeks after starting Levothyroxine. Arrange an early morning and fasting (water only) blood draw when TSH is highest, and take Levothyroxine after your blood draw.


I am not a medical professional and this information is not intended to be a substitute for medical advice from your own doctor. Please check with your personal physician before applying any of these suggestions.


Thank you. I don't understand the who T3 & T4 stuff, it's not been explained to me by my doctor regarding the hormones and levels and what mine are - - all I know is my throid levels are really low at the moment. Starting on a new dose of 75mgs of levothyroxine tomorrow and I have to return to my doctor for a blood test in 4 weeks. I'm hoping I feel like there is an improvement by then :) Thank you for your help / advice. I really appreciate it x


Get on the internet and research the "whole T3 & T4 stuff", your health and feeling of well being will depend upon your understanding of how this all works together. It took me about 6 months of manic dedication to learn about the thyroid system and I am not "biological" at all. However, you must understand what is going on. Start with the internet then read a book called "Stop the Thyroid Madness" (yes it's a silly title IMO) but it's a good book. There is another book by Barbara Lougheed called Tired Thyroid, quite an eyeopener. And, of course, you will learn a lot from this site.

Once you know what is going on, (and you are the best person to know because you feel the symptoms), you can be in control of what happens to you. The alternative is to spend weeks, months and even years on the wrong dose of the wrong brand of the wrong medicine prescribed by a well meaning but under educated medic who probably doesn't know there is a difference.

Good luck in your studies, you will find it fascinating and ask all of your questions here.

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