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Thyroid UK
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How long does it take levothyroxine to start working?

Hello there. I've never posted to a forum like this. I'd value a bit of a share if there's anyone out there listening :-)

I visited my GP recently because I was growing increasingly weary, foggy headed and low in spirits. My default setting once I stopped doing anything that was essential was 'collapse in bed'. I started gaining weight.

My GP has just diagnosed me (two days ago) with hypothyroidism and vitamin D deficiency. I've been prescribed Vitamin D and a daily 25g dose of levothyroxine.

I long to know how soon these supplements may affect my symptoms which are really debilitating.

I can't help but feel that I'm simply being lazy and self pitying because I have such difficulty just doing the normal stuff and feel so low. I've grown really irritable, even my best friend is annoying me and I'd rather not see her till I get my oomph back.

Only how long will I have to wait?

Is it better to give in to the fatigue and rest, or fight it all the way?

I feel lonely, because everyone else is bouncing around and I'm glued. If I say I have hypothyroidism, I secretly feel I'm making up an excuse for being lazy and feel sure they think the same.

Any wise words appreciated.

Many thanks


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14 Replies

Hi Fran,

Welcome to our forum and we are listening ......

.... Levothyroxine takes up to 6 weeks to initially saturate the body which will only tolerate small increases at any one time. Your doctor should retest your thyroid hormone levels after 6 weeks and adjust the dose according to results. Leave 24 hours between last dose and blood test draw and have the blood drawn early in the morning whilst fasting (water only) as this is when TSH is highest.

Be aware that sometimes a low dose 25mcg Levo can make a struggling thyroid gland take a bit of a break and produce even less than it was, so intensifying symptoms . It is important to take your pill on an empty stomach with a glass of water, 1 hour before food, 2 hours before supplements and 4 hours before calcium, iron or vit D supplements.

Depending on how long your hypothyroidism has remained undiagnosed, your symptoms may continue for a while, but you should start to see an improvement once you are wholly medicated. The goal of Levothyroxine is to restore the patient to euthyroid status and for most people that means TSH just above or below 1.0. Symptoms can lag behind good biochemistry by 6-8 weeks.

People with thyroid issues often have vitamin deficiencies and you are now supplementing Vit D but should also ask your doctor to test Vit B12, folate and ferritin as optimum levels are required to ensure good thyroid hormone synthesis.

A good book to read is "Your Thyroid & How To Keep It Healthy" by Dr Barry Durrant Peatfield. It is soon better to ACCEPT and REST until thyroid hormones are optimal. Were you tested for thyroid antibodies ? ?....





This following link explains the importance of vitamins and where they may be obtained.



Thanks so much for this kind and supportive reply :-)


Believe me when I say if I don't get the right meds I feel positively sedated, so you're not making anything up, this is a real illness which can for some people be relatively symptom-free and for others can be devastating.

I can't add much to the reply above, except to say you may feel worse on 25mcg. I would expect/request a fairly quick turnaround on another blood test and dose adjustment, maybe six weeks? Not six months. Sometimes we get our 25mcg levo and are forgotten about, so just keep an eye on that.

It would be helpful for you to get a copy of your test results from your gp, along with the lab ranges. Would also be good to know how low your vit d is and how much you're taking. I was severely deficient and my gp suggested I take 800 units per day, which just doesn't cut it unless you're healthy and just supplementing.

It will get better though! Sometimes it just takes some tweaking.

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Dear Punctured Bicycle,

Thanks so for your kind support. It's really helpful to hear other peoples experiences.

My GP did say that he was starting me on a very low dose, and asked me to return in 6 weeks to see if it was enough. He communicated well with me, I think, given they have limited time. I guess these days they know we have this amazing internet to find out more. You wonder how we all managed without it sometimes!

Thanks for the advice, I'll ask for a copy of my test results. It'd be helpful to know if my thyroxin and vitamin D levels were way off beam or just a little bit. I think the doctor mentioned my pituitary was having to fire off five times harder than it would be to kick my thyroid into action or something along those lines.

It's great to know treatment has helped you. Do you feel fine now?



Fran, it has been an up and down experience. Levo alone made an improvement of about 20%, and then adding in a little t3 (liothyronine) helped me get to about 60-80% depending on what day it is.

I am no longer always cold and sleepy, my hair and brows are back, when I reduce my food intake I'm able to lose weight, my gut works pretty well and I'm fairly cheerful much of the time.

I still lack some mental clarity, eg when I want to start and/or complete a task it's hard for me to find the end of the thread sometimes. Some of that is lacking motivation, some may be laziness :-) and maybe perimenopause isn't helping. I forget names (just my age possibly) and can be easily distracted, and I can't really count on my energy/stamina.

Not sure if that gives you a good idea of how my life has changed, but it is probably not as bad as it sounds. An awful lot of people (for instance a friend of mine who just had a thyroidectomy) get on their meds and get on with their lives. But it isn't an imaginary illness or laziness!

I wish you luck!


To get fully back to normal takes around a year once you're on the right dose. You will improve month on month but the thyroid hormones stored in your cells will be depleted and it takes a while for the blood to top them back up again. I had good and bad days while I was recovering. Sometimes I felt worse than before diagnosis but after about a year and a half (I needed to swap from levo to ndt because I have a gene mutation that means I don't convert levo as well as someone normal so my recovery took a bit longer) I realised that I was back to being me

Good luck


Hi TupennyRush

Many thanks for your kind message. I love the picture of you returning to be being you month by month, thanks for putting that happy picture in my mind :-D

Cross fingers my experience will be similar. At present I feel like I am carrying a very heavy rucksack everywhere and come the afternoon it's all I can do to stay upright. And it's incredibly difficult not to admonish myself for being lazy if I accept it and lie down and rest in the middle of the day when I know I ought to be doing a thousand other things.

Still, I don't mind if it takes a long time to restore, so long as I can feel things going in the right direction. I need to be a bit more patient! I take a levothyroxine pill each morning and start drumming my fingers waiting for a surge of fresh energy :-)




Really sympathise with how you are feeling. I wish someone had spelled out to me how much patience was required to get well when I was first diagnosed. Instead my GP gave me thyroxine and told I was going to be feeling so much better so quickly. It didn't happen. To cut a long story short it took me about 2 years to get well - my GP didn't believe in vitamin D deficiency and I had to find out about that for myself. Once I started that things improved quickly. Going gluten free was the final piece in my personal jigsaw - something you might like to think about in time. If you have time you might like to take a look at these online videos hopeforhashimotos.com/hashi... I think they give a good explanation of how your body reacts as you start the journey of taking Levo. They are specifically about Hashomoto's Thyroiditis and you don't say if that was your diagnosis, but regardless I think they are relevant to anyone taking Levo.

As you are already getting vitamin D supplements hopefully you will start to feel better soon. You must be good to yourself and not feel guilty that you don't have much energy at the moment. One thing people on here often feel is that possbly it is all "in our heads" - it isn't, you have to take time and get well. Listen to your body and take good care of yourself.

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Hi Pink Bear,

Thanks so much for your kind words.

To be honest I've felt in need of a bit of sympathy, and goodness, a little goes a long way. It's not like you need loads, just a wee bit to get you up off your feet now and again.

I was standing in a yesterday cafe waiting for the loo and a bloke walking past asked me if I was OK and just lightly touched my elbow kindly. I said yes I was fine, of course, still the little touch on my elbow was an incredible help and seemed like just what I was longing for.

My friends and family are saying the right words, but I'm not feeling the acknowledgement or support. Strangers like you are more genuinely supportive, and my goodness it helps. Thanks again, and so glad to hear you are feeling better :-)




Thank you for such a heart warming reply. This is great place to find help and support - there's always somone who will listen.

For me,some symptoms went fast ,but it took a year to feel much better but a couple of symptoms remain.25'mcg is a very small starter dose .Have another blood test in 6-8 weeks and post the results with ranges shown in brackets.

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Hi Treepie,

Thanks for your message. Really pleased to hear you're feeling better, even if it took about a year!

I'm going to get my blood test results to have a closer look at them. I'll post them like you suggested!



Hi Fran1962

My words of wisdom are:

Listen to these guys, they know what they are talking about - I neglected myself for too long before I found the forum

Make sure you get regular blood tests and post them here - I hadn't had a blood test for 14 months until I came on here and they gave me the confidence and kick I needed.

Don't let your GP ignore you if you feel unwell persist. My GP said everything was fine with thyroid and there are many reasons for 'tiredness'. Tiredness does not even cover it. I quoted from the forum of what I though I should be on and also that of a PMI GP, she finally gave in, that's where I am at the moment waiting the 6-8 weeks for it to make a difference.

If you are unhappy with your GP, change - that's where I am as I have lost confidence in mine. I am hopefully changing to a GP that specialising in thyroid.

Finally do not neglect yourself - I did for 2 1/2 years and it's not fun. I now have a plan and sorting my health out thanks to this forum.

All the best and congrats on find the forum so early !


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Hi D

Thank you for sharing your experiences with me ~ so helpful :-) I think you made a good call to change your GP. They really vary don't they?

One of the GPs in our practice is the rudest and least helpful I've ever encountered. One is the kindest soul, though always really vague about explanations and solutions. One is both kind and clever and communicates very well. Thankfully, I see the one!

You're so right about having a plan to take care of ourselves generally, so that we're approaching recovery using every resource available to us. I've joined weightwatchers to try and shed some of the weight I've gained. They're really good. I feel positive about what I eat now, at least, even though I've only lost a couple of pounds.

It was after Weightwatchers spurred me to exercise and I foud it practically impossible to jog that I went to my doctor and received my diagnosis. I usually enjoy gentle exercise and everything was telling me that something wasn't normal there.

Thanks again D



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