Log in
Thyroid UK
91,932 members106,197 posts

How long for Levothyroxine to start working?

Hello everyone, this is my first post here as I've recently been diagnosed as having hypothyroidism.

A little background; I went to the doctors because I started getting joint pain in my fingers and I was becoming ridiculously tired all day and living on energy drinks. I'd been dieting for a year so put it down to maybe reduced energy levels and maybe arthritis.

Anywho, after a couple of blood tests the doctor said I had hypothyroidism and put me on 25mg of Levothyroxine.

I've been on them for nine days now but I'm still tired and have problems waking up. In fact yesterday I fell asleep in the afternoon and the battery on my phone ran out so the alarms didn't go off and slept through picking my son up from school so much that I didn't wake up until it was 5:30pm when the inlaws were banging on the door.

They and school were pretty angry understandably, to say I'm utterly mortified and upset is an understatement.

Does anyone know how long it might take for me to feel an improvement as I'm getting a little down about it now?

Thanks for any advice you could give.

6 Replies

Welcome to the forum, DanW.

It take 7-10 days for Levothyroxine to be absorbed before it starts working, and up to six weeks to feel the full impact of the dose. 25mcg is a starting dose because thyroid hormone has to be built up gradually. You should have a follow up thyroid test 6-8 weeks after starting Levothyroxine as you'll probably need a dose increase. Arrange the blood draw early in the morning when TSH is highest, and fast (water only) because TSH drops post-prandially.

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

Ask your GP to check ferritin, vitamin D, B12 and folate at your next thyroid blood test. Hypothyroid patient are often low/deficient and that can cause muscle and joint pain, fatigue and low mood similar to hypothyroid symptoms.

Ask for a printout of your results with the lab ref ranges (figures in brackets after results) after blood tests. You can post them in a new question for comment and advice.



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


Thankyou for the reply.

I have my blood tests at 9am each time.

After some reading here I may have made the mistake of swapping to taking the dose in the morning as I was taking them at night but I didn't realise the issues surrounding dairy products (and maybe coffee?).

My doctor has asked that I go back to them for another test in three months (although I only have a supply to last two months) so should I be going back earlier?

My test results for calcium levels were low so I got a calcium and vit d supplement which I take in the mornings so maybe that also interfered with my Levothyroxine?

I changed to taking it in the morning because when I took it at night it was making me jittery and excitable like I'd had a strong coffee and I wasn't getting to sleep well, but I guess I'd better go back to that system.

Thanks again.


DanW, you can take Levothyroxine any time of day or night as long as you take it away from food etc. as outlined above. VitD is best taken with the fattiest meal of the day as fat helps absorption.


When I started back on thyroxine I was sleeping for England for about a fortnight. The doctor said it's quite normal for this, and other side effects, while my body rebuilds itself and repairs all the damage done by not being on the thyroxine for so long while I needed to be.

I happened to mention how much the pain in my Achilles and joints had improved since restarting on the meds to my sister in law (an NHS nurse) and she said it's due to lack of calcium - hypo stops you absorbing it correctly, apparently - and she said I should switch back to full fat milk for a few months, instead of the 1% or semi skimmed I usually drink, or until the pain goes away. The doctor didn't mention this, and I haven't seen it mentioned anywhere. This was only on Tuesday, so today's my first day back on fat chuffer milk, but hopefully I'll see an improvement soon? Hope so, I'm attempting a fell race in Yorkshire tomorrow, my first for a few months.


Achilles_Pain, I doubt a few days of full fat milk will have made an appreciable difference. Good luck with the fell race tomorrow!


Thanks again and good luck with your race tomorrow. I've started taking the thyroxine at night again as it won't be near any other substances that might affect its absorption.

The last few days have been horrible with tiredness and sleeping but today has been a little better.

Do you think I should make an appointment with the GP at six weeks then or should I go back in three months like the GP asked?


You may also like...