Low T3 and T4 on levothyroxine: Hello, I am on... - Thyroid UK

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Low T3 and T4 on levothyroxine


I am on levothyroxine for 4 months 25mcg/50mcg on alternate days because my TSH was 3.20 miu/L.I have problems with fertility and miscarriages.

My last results:

TSH (0,35-4,94) 0.55 miu/L

T3 (2,63-5,70) 3,92 pmo/L

T4 (9,01-19,05) 10,30 pmol/L

My t3 and t4 are to low, but my TSH is ok and my endricologist think that is ok.This month a have problems with my period it is 4 days late.I think is levotyroxine.

What I should do?If I increase dose of levothyroxine my TSH will be to low.

9 Replies

Do you have TSH, fT3, fT4 results from before you were on levothyroxine?

I think your problem is that your TSH is too low for your fT3, fT4 combination. There can be many reasons for TSH being insufficient. The endocrinologist should look into why there is an inconsistency between your TSH and thyroid hormone levels. Usually, as fT4 starts to fall TSH shoots up. This is why TSH can be such a good marker for thyroid gland failure. Unfortunately, whilst endocrinologists are always pointing out how sensitive the TSH response is they fail to act when this expected response is missing. I suspect you will need more levothyroxine and some liothyronine (L-T3) as an insufficient TSH reduces T4 to T3 conversion.

I have a collection of posts like yours I've taken from the forums (which I keep private) and there are now over 50 such cases. I plan to do a detailed write up on this which should be available later this year.


My results before levotyroxine were:

December 2018-diferent lab

TSH 3,23 (0,46-4,68)

T3 2,98 (4,26-8,10)

T4 14,80 (10-28.2)

March 2018

TSH 1,18 (0,35-4,94)

T4 13,26 (9,01-19,05)

T3 3,08 (2,89-4,88)

I also have hashimoto.I started with dose of levotyroxune 50mcg, after one month my TSH was 0,33 (0,46-4,68).Because it was to low, my dose was changed to 25mcg/5omcg on alternate days.


These results really confirm that your TSH is insufficient and probably affecting your conversion of T4 to T3, specifically 'type-2 deiodinase', especially your December results. If you were recovering from a serious illness it could explain these results and things might get better in time. Alternative explanations could be if you are very depressed or on an almost starvation diet. Assuming none of these apply the most likely factor is that due to your autoimmune hypothyrodism (Hashimoto's) that perhaps you were hyperthyroid for some time and this has down-regulated your thyrotrope, the part of the pituitary that produces TSH.

Whatever the reason you need more thyroid hormone, probably some T3. They can't rely on TSH because your pituitary is not producing as much TSH as it should given your low normal fT3, fT4 levels. Endocrinologists are keen to tell us how wonderfully sensitive the TSH response is (it is for healthy people) but never consider how to treat patients when this mechanism fails. I would confront your endocrinologist (in a friendly way) and say 'look, these hormone levels are low normal but my TSH is responding as it should'. Best of luck!


Endocronologist don't care until t3 and t4 are are in reference range and TSH is in normal range.I already ask about low t3 and t4 but she think that is ok. I will ad some t3 by my own and then check my levels again.


Try taking L-T3 at breakfast and bedtime. Initially 10 mcg daily (2x5), you can split 20 or 25 mcg tablets. Your fT4 will go down after you start L-T3 as your lower TSH will reduce thyroid stimulation (you probably have some thyroid function).

I'd strongly recommend you gather some evidence of your current status so that you can compare in the future and use to educate doctors. Take some photos of yourself, your weight, list of symptoms and signs like dry hands or soft nails.


As you have Hashimoto's it's absolutely essential to regularly test vitamin D, folate, ferritin and B12

add these results and ranges too if you have them

Hashimoto's affects the gut and leads to low stomach acid and then low vitamin levels

Low vitamin levels affect Thyroid hormone working

Low vitamins tend to lower TSH

Vitamins need to be optimal for good thyroid function

Poor gut function can lead leaky gut (literally holes in gut wall) this can cause food intolerances. Most common by far is gluten. Dairy is second most common.

According to Izabella Wentz the Thyroid Pharmacist approx 5% with Hashimoto's are coeliac, but over 80% find gluten free diet helps, sometimes significantly. Either due to direct gluten intolerance (no test available) or due to leaky gut and gluten causing molecular mimicry (see Amy Myers link)

Changing to a strictly gluten free diet may help reduce symptoms, help gut heal and slowly lower TPO antibodies

Ideally ask GP for coeliac blood test first or buy test online for under £20, just to rule it out first

Assuming test is negative you can immediately go on strictly gluten free diet

(If test is positive you will need to remain on high gluten diet until endoscopy, maximum 6 weeks wait officially)

Trying gluten free diet for 3-6 months. If no noticeable improvement then reintroduce gluten and see if symptoms get worse








I am gluten and dairy free for one year now.My TPO antibodies lower, bit still high.I also check my vitamin levels and are ok, I am using supplements.


What are your actual results and ranges on vitamins?


Vitamin d 85 nmol/L (18-142)

Vitamin b12 650 pmol/L (138-652)

Ferritin 64 ug/L (10-120)

Folic acid 42nmol/L (7-46,4)


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