Starting levothyroxine, dose too low? - Thyroid UK

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Starting levothyroxine, dose too low?


Hi, this is my first post, I was diagnosed hypothyroid last week, my results sheets says TSH of 26.4 (mU/L 0.30-6.00) and free T4 of 8.6 (pmol/L 10.0-22.0) - not quite sure what the numbers mean, but anyway my gp has put me on one 25mcg levothyroxine tablet per day and told me to get my bloods retested in six weeks.

Looking at the other posts I am just worried in case this is too low and I might not see much improvement in six weeks? Any advice would be appreciated!

12 Replies

Yes 50mcg is the usual starting dose if you have no other health issues. However it is good that you are being re-tested in 6 weeks. Many GP's leave it much longer - too long sometimes.

The FT4 is the hormone that your thyroid produces and it is a storage hormone and needs to convert into the ACTIVE thyroid hormone T3 - which has not been tested. Yours will be low due to the low T4.

Your anti-bodies have not been tested either - Anti-TPO and Anti-Tg. Also ask for the following tests - B12 - Ferritin - Folate - VitD. All need to be optimal for your thyroid hormones to work in the body and for you to feel well.

Be patient and be prepared for things to move slowly - it does of course depend how long you have been Hypo - as to how quickly you will respond.

Are you on any other meds for other conditions ? Do you have any gut issues ?

Sorry for the questions - it would help others if you had completed your Profile with some information. I see you have suffered with Endometriosis - which I believe can be connected to the Thyroid.

Cbed in reply to Marz

Hi - Thanks for that reply. I am not sure what else was tested, I will find out today as I am going back to a different gp to just ask about the dosage levels. No, I'm not on any other meds and don't have any gut issues, and it's v interesting to learn endometriosis is connected, had no idea! I will post again once I've been to the gp.

Marz in reply to Cbed

Cbed in reply to Marz


Welcome to the forum, Cbed.

Thyroid Stimulating Hormone (TSH) is a pituitary hormone which rises when thyroid hormones (T4 and T3) are low, and drops when sufficient T4 and T3 are detected.

Free T4 is the amount of T4 unbound to proteins an available for cellular use.

Your TSH is very elevated because FT4 is very low. 25mcg is a very conservative dose and if you are <50 years of age without ischaemic heart disease it may have been more appropriate to prescribe 75mcg-100mcg as a starting dose.

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.

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.

Most people will find symptoms resolve after their TSH drops to around 1.0 with FT4 in the upper range but symptoms can lag a couple of months behind good biochemistry.


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.

Cbed in reply to Clutter

Hi thanks for the reply, I did suspect it was a bit of a conservative dose to start with and am going to ask about that today. Thanks for putting that link on from NICE too, that should help me when I ask! this has all been really useful information.

HiddenThis reply has been deleted
Cbed in reply to Hidden

Oh ok. Thanks I will watch for this.


How old are you?

Cbed in reply to Hidden

Hi I am 43

Hidden in reply to Cbed

So as Clutter says the starting dose is 50 for those under 50.

Cbed in reply to Hidden

Ok so I have now had my dosage raised to 50 mcg per day, will see how this goes. Thanks for everyone's help.

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