Thyroid UK
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Lost again

I take 300 mg of thyroxine and have done for a few years but I still feel so unwell.

Just got my lab results back.

Can anyone comment?

Serum TSH level. 3.76 mIU/l. (0.27 - 4.20)

Free triiodothyronine. 5.1 pmol. (3.9-6.7)

Serum free T4 leval. 18.7 pmol (12.0-22.0)

I have been getting all the symptoms of a thyroid problem but every time I ask the doctor they say it is normal

B12 is normal plus all other tests?

Can anyone help?


8 Replies

Ian, TSH 3.76 is in the normal ref range but it is too high for some on replacement hormone and you need an increase in Levothyroxine. Most feel comfortable with a TSH just above or below 1.0. Scroll down to Guidelines and Treatment Options to read Dr. A. Toft's comments

Email if you want a copy of the article to show your GP.

B12 normal can range from 141-2000. You need to know what yours is and where in the ref range it is and ditto other vits/minerals. Get a print out of your results with the lab ref ranges (the figures in brackets after your results) and post them in a new question for comment/advice.


Thanks for your help.



What is B12? Also ferritin and folate?

Your blood levels are actually good. So there must be something else going on. The fact that TSH is high given T4 dose is a bit weird. For some reason your pituitary gland has decided that good is not good enough. But at 300 mcg T4 there must be an absorption issue. Any thoughts of eliminating gluten from the diet? Any chronic damage to the villi of the small intestine will also interfere with absorption of T4.

I don't quite agree with Clutter because your levels are good. Your TSH is high considering your fT3 and fT4 are good.

Alcohol and whatnot will screw up stuff. Taking a B-50 complex will help to increase levels of all Bs. You also need to get some quality protein. Depending on your weight 60 - 75 grams per day is good.

I'm assuming your blood glucose is normal? Bouncing blood glucose will make a person feel like poop too.

Any possibility of sleep apnea or hypopnea?


Here are some excerpts from How Stuff Works, Thyroid Metabolism:

"Incomplete conversion of T4 to T3 can also lead to low thyroid symptoms. Factors such as nutritional deficiencies and medications can inhibit this conversion. Nutritional deficiencies such as iodine, iron, selenium, zinc, vitamin A, riboflavin, pyridoxine and B12, along with the use of certain medications including beta blockers, birth control pills, estrogen, iodinated contrast agents, lithium, phenytoin and theophylline can inhibit the conversion of T4 into T3. Other factors that can cause this inhibition include aging, alcohol, alpha-lipoic acid, diabetes, fluoride, lead, mercury, pesticides, radiation, stress and surgery [Source: Brownstein].

Problems can arise if T4 is converted preferentially to reverse T3. Reverse T3 can bind to the T3 receptor, but it only has 1 percent of the activity of T3. T4 is normally converted into equal amounts of T3 and reverse T3. However, if there is a preferential conversion of T4 to reverse T3, the reverse T3 can act as an antagonist to T3 at the receptor level. This scenario leads to symptoms of low thyroid since reverse T3 can be considered inactive. Factors that may lead to a preferential conversion to reverse T3 include high cortisol, glucocorticoids, stress, excess estrogen and nutritional deficiencies such as selenium, iodine, zinc and iron [Source: Paoletti].

Cortisol levels need to be within normal range (morning saliva level of 3.7 to 9.5 ng/mL) and vitamin D levels need to be between 50 to 70 ng/mL for thyroid receptors to respond properly. Iron also plays an important role in thyroid hormone synthesis. Thyroid peroxidase activity depends on iron; therefore, iron deficiency could lead to hypothyroidism. Ferritin levels may need to be in the range of 90-110 to achieve proper thyroid function [Source: Paoletti].

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I'm going to add another thought into the mix. I don't see a conversion problem, which often shows as FT4 relatively high in Range and FT3 relatively low in range. Your FT3 is 43% of range and your FT4 is 67% of range. A bit of a disparity but of more concern I would say, is how low your FT4 is given the amount of thyroxine you are taking.

I would suggest an absorption issue.

Do you take all your thyroxine at once? If so, may I suggest you try splitting it into 3 doses.

I wonder if liquid thyroxine might be more easily absorbed?

I don't know what can cause absorption issues. My first guess would be gut problems - perhaps candida, leaky gut, IBS. I don't know.

Maybe get tested for candida. Something's going on. As usual, the problem is finding it.

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Thank you for your help


From my personal experience I let these tablets dissolve in my mouth and find this is far more effective for me personally than trying to absorb through the stomach. Absorption of T4 varies between 41 and 79% dependent on the chemistry of the gut and the coatings of the tablets the makers use. You may be taking 300 but not absorbing it. Fasting does increase absorption too.

Look at your heart rate body temp blood pressure, and all your clinical symptoms now then change how you take the tablets it definately helped me.

Another thought on this a normal thyroid gland contains 200 mcg of T4 and 15 mcg of hormone per gram. However what circulates in your body can be a lot different.

I am always trying different things to help me to get the maximum absorption and I definately split the dose.

Hope this helps as I have been there too.



Thank you so much.

It does make sence. Never thought about it in that way.



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