100mcg of Levothyroxine, low or high? - Thyroid UK

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100mcg of Levothyroxine, low or high?

misfits73 profile image

According to my GP the thyroid levels are normal for the last 5 years (TSH <2mIU/L, FT3~4.5pmol/L and FT4~15pmol/L).It took 2 years prior to normalise to these levels.

The dosage these 5 years is 100mcg of Levothyroxine.

I'm not feeling very well (tired, weight gain as i'm craving carbs, internal shakiness, insomnia etc.) but i thought it was anxiety related symptoms so i live like that all these years.

A friend said that maybe the dosage is not right, told that to my GP but he insisted the dosage is right.

What's your opinion about this "maintenance" dosage and the symptoms i'm going through?


20 Replies


Also have you got results from your latest vitamin D, vitamin B12 and folate tests? If so post those and the ranges.

If you haven't got them then go and get tested. If your GP refuses to do the test get a Blue Horizon plus 11 test.

There are a few posters on here who feel terrible and it's one of the vitamins or mineral mentioned.

misfits73 profile image
misfits73 in reply to bluebug

Checked all Vitamin levels as well, D=32.2nmol/L, B12=385pg/mL, Folate=3.2ng/mL.Normal range in the NHS for vitamin D is 80-150nmol/L.

Previous D level was 26 and folate 2.9 (4 months ago).There is a slight increase after he put me on supplements (800IU of D and 5mg of folate) but i was expecting these low levels as i live in the UK and there is not enough sunshine so i don't pay attention in the vitamins part or should i ?

greygoose profile image
greygoose in reply to misfits73

You most certainly should! If your vitamins and minerals are low, your body will not be able to use the hormone you are giving it.

Hi, do you have the ranges for the FT4 and the FT3? It would help enormously if you have.

When your doctor says 'normal', he doesn't actually mean 'normal', he means 'in range'. But, 'in range' isn't the same as 'optimal'. And, to feel well, you need your FT3 to be 'optimal'. At the moment, it obviously isn't, because you still have symptoms.

You have to remember, that doctors know nothing about thyroid. They hardly touch on it in med school. They don't understand the subtleties, and have no idea how bad low thyroid makes us feel. That is why you have to learn as much as you can about your disease, and take charge of your own health. And educate your doctor if at all possible.

Difficult to say for certain, but even without the ranges, your FT3 looks a bit low. Possible you aren't converting very well. And that's a very strange TSH result. Can you not be a bit more precise?

Have you had your vit d, vit B12, folate and ferritin tested? They all need to be optimal - not just in range - for your body to be able to absorb and convert the T4 you are giving it. So, best to get those tested, and supplement any that are low. You won't get any help with that from your doctor, because they know nothing about nutrients, either!

100 mcg is more or less a starter dose, so you really do need an increase. But the difficulty will be persuading your doctor that bottom of the range just isn't good enough. You want your FT3 to be somewhere up near the top of the range - somewhere where it makes you feel good! 5 years is just too long on a starter dose. :)

Maybe ask to see an endo they understand thyroid better than GP.

Is this reply to me? Or the OP? I don't need an endo. Never met one that understood thyroid, anyway. The vast majority of endos are diabetes specialists who know next to nothing about thyroid.

But, you do realise that this post is two years old? Hopefully, the OP will have sorted out her problems by now. :)

Results : Range:

TSH= 1.96 0.34-4.94mIU/L

FT3=4.3 2.63-5.7pmol/L

FT4=15.3 9.01-19.05pmol/L

Vitamin D=32.2 80-150nmol/L

Vitamin B12=385 187-883nmol/L

Folate acid=3.2 3.1-20.50ng/mL

Currently on Levothyroxine 100mcg, Vitamin D 800IU and Folate 5mg a day

SeasideSusie profile image

misfits73 Vitamin D needs to come up to at least 100. You need more than the 800iu your doctor is giving you. I would buy your own and supplement 5000iu daily until you reach your target level, then drop down to a maintenance dose of maybe 2000iu daily. Keep a check on levels by private testing if necessary, £28 for a fingerprick blood spot test with City Assays, after a few months.

B12 needs to be around 1000. Supplement with Solgar or Jarrows sublingual methylcobalamin lozenges.

When taking B12 you need to take a B Complex to balance the B Vits. Thorne Basic B is a good one and contains 400mcg folate which will address your dire folate level.

It's very likely that your ferritin level is low also considering all the others are. Have you had it tested? If not ask your GP if he will test. It needs to be at least 70, prefer100+, for your thyroid hormone to work.

It's also a good idea to supplement with selenium as it helps conversion of T4 to T3.

Just found the ferritin results: 100ng/mL with a range of 22-275ng/mL.

So you are saying it's more likely a Vitamin related issue rather than the 100mcg of Levo?

SeasideSusie profile image
SeasideSusieAdministrator in reply to misfits73


Your latest thyroid test results:

TSH= 1.96 0.34-4.94mIU/L - with a treated hypo patient the aim is to get the TSH down to 1 or below or wherever it needs to be for the FT4 and FT3 to be in the upper part of their ranges.

FT3=4.3 2.63-5.7pmol/L - is approx 54% through the range

FT4=15.3 9.01-19.05pmol/L- is approx 63% through the range

T4 is converting to T3 but as T3 should be a bit higher in it's range than T4 is in it's range, then FT3 could be a bit higher.

Optimal levels of vitamins and minerals are needed for thyroid hormone to work properly. Your ferritin is good, could perhaps be a bit higher, 100-130 is best, so you don't have to worry too much about that. BUT all your other Vits and mins are poor, far too low in their ranges and you need to supplement to get ALL of them at their optimal levels. Add in selenium to help with conversion and you could very well find that your thyroxine will work better, your TSH might drop a bit and your FT4 and FT3 might increase.

One other thing to consider is are you absorbing nutrients. Many hypo patients have low stomach acid which prevents proper absorption. Increasing stomach acid by using Organic Apple Cider Vinegar With Mother diluted in warm water before meals can help, or taking Betaine HCl with Pepsin.

So to answer your question, yes, it could very well be a vitamin related issue. You need to get them all to their optimal levels, Vit D, B12 and folate all desperately need to be addressed.

You say you are craving carbs. People tend to crave the things they are intolerant or sensitive to. Your internal shakiness could be low blood sugar. I don't know enough about those to comment.

radd profile image
radd in reply to SeasideSusie

SSS & misfits73

Carb cravings can be down to low blood sugar caused by insulin resistance when sugar is unable to enter the cells although high in circulation.

When blood sugar falls too low (hypoglycemia), the adrenal glands release stress hormones to signal the liver to break down proteins and fats for energy (this causes a lot of bodily stress and inflammation) by stimulating the use of glycogen (stored sugar in the liver). The body then tells itself to lower metabolism in order to preserve energy, meaning slowing down thyroid hormone synthesis.

Also continually elevated cortisol levels can impair the HPT axis by suppressing pituitary function (so not signalling the release of enough thyroid hormone) and because thyroid hormones drive our metabolism, a low level can slow glucose absorption in the gut and the rate our cells uptake glucose. It can also slow the response of insulin secretion and the clearance of too much in the blood.

Never let yourself get too hungry. Eat regular healthy meals that include protein, healthy fats and low GI carbs. Protein is hugely important as tyrosine (an amino acid from dietary proteins) is one of the important components of thyroid hormone. It is also filling and takes longer to digest so keeping you feeling full for longer.

Also eat any sweet fruits with protein to stop the blood sugar troughs & dips, such as an apple with cheese, grapes with yogurt, pear with nuts, etc. I eat protein with every meal and keep Pulsin Protein bars in my bag/car for when I get caught out.

I eat a delicious banana pancake for breakfast (receipe from a member) made with nothing but whisked up banana & egg. Protein is fattening and too much is counterproductive as hard on the liver but a small steady supply throughout the day is perfect.

SlowDragon profile image

Agreeing with all the previous answers - it is essential to address the low vitamins and minerals first and if hypo we mostly need TSH of around or just under 1.

One the other thing to consider is have you had your thyroid antibodies tested? There are two sorts TPO and TG - they BOTH need checking as you can have high levels of one or the other or both. GP's rarely do TPO and almost never will agree to checking TG antibodies. This is why so many of us resort to private blood tests to cover the full vitamins, antibodies and thyroid tests. (I, like many others, use Blue Horizon thyroid plus eleven test - includes vitamin D)


If the antibodies are high (above range) then this means that the thyroid problem is autoimmune - called Hashimotos. This is most common cause by far of hypothyroid problems.

GP's and endo's don't really address the autoimmune aspect - they just replace the missing hormones with Levothyroxine.

Many Hashimotos patients find that by adopting a 100% gluten free diet this can reduce symptoms, calm down the immune reaction and even sometimes lower the antibodies. Something to consider once you get a bit more sorted, if you have hashimotos.

My endo told me that we use/need a minimum of 2000IU of vitamin D a day - so a replacement dose of 800IU is not going to improve things much (unless you sit out in sun every possible moment to top up that way).

Hi misfits73. This sounds like me. I'd been on 100mcg for many years and this past March, I began to slowly develop hyperthyroidism symptoms.......like you mentioned..... the same jittery stomach and hungry all the time... lost weight.. till I began to feel very bad.. even felt like my head was in a vice. I felt awful.

It took a bit of work, but I remembered a similar but kinder episode I'd experienced a few years back though and back then my doctor had told me that I could have cut down my 100mcg levothyroxine to half. So thinking back to that experience, i did exactly this on my own ... I cut my dosage to 1/4 or .25 mcg and I began to feel better. I then made an app. with my doctor. I was tested and at the time, my blood test read 8.9ml/ IU. My doctor was all set to give me a prescription for a higher dosage of Levothyroxine ... that is, 125mcg. But I told her that if I were to take this I'd be jumping up and down, thus my reason for cutting back. So after our talk, we concluded that I keep on taking about 25mcg of 100mcg dosage. I was happy that my doctor listened. I was feeling better in no time.

A couple of weeks ago, I decided to do some experimenting by raising my dosage to 75mcg. That did not go over well at all so I went back to .25mcg and working it back up to 50mcg now.

I also spoke to my pharmacist. He assured me that the Levothyroxine was made by the same Canadian company... same ingredients etc., but what's important is what he told me afterwards. "When our TSH is high, it is because our thyroid gland is making more natural hormone so this is why we need less Levothyroxine." So we need less, not more. Doctors need to know this.

I have to add that I also felt very tired and by cutting back on my dosage to .25mcg, the tiredness also went away. When I upped it to 75 mcg, the tiredness returned. I also felt tired but had could not sleep. Just hoping my story helps somebody... Thanks for this site and to everyone who helped me

I have to add that I also felt very tired and by cutting back on my dosage to .25mcg, the tiredness also went away. When I upped it to 75 mcg, the tiredness returned. Sorry, hope this appears below my previous letter.

Thank you all for your helpful answers, much appreciated.

I have some more questions if you don't mind:

-Since my thyroid story started 8 years ago and the hormone levels are within range what is the doctor trying to achieve having me on medication still?

-Levo medication affects TSH only or FT3 and FT4 as well and how?

-Increasing the low vitamin levels will they affect the thyroid ones and how?



Clutter profile image
Clutter in reply to misfits73


It's better to write a new post with questions than to tag them onto the end of an existing post as updated posts don't get much visibility. I caught this by chance.

-Since my thyroid story started 8 years ago and the hormone levels are within range what is the doctor trying to achieve having me on medication still?

Without medication your thyroid levels would become deranged. Medication replaces low thyroid hormone, it's not a cure, you'll need to continue taking it for the rest of your life.

-Levo medication affects TSH only or FT3 and FT4 as well and how?

Levothyroxine raises T4 which converts to T3. Raising FT4 and FT3 lowers TSH.

-Increasing the low vitamin levels will they affect the thyroid ones and how?

Selenium is thyroid friendly and improves thyroid function. Good levels of iron aid absorption and uptake of thyroid medication although iron has to be taken 4 hours away from Levothyroxine. Good levels of vitamin D aid conversion of T4 to T3.

misfits73 profile image
misfits73 in reply to Clutter

Is there a recommended dose for Selenium?

helvella profile image
helvellaAdministrator in reply to misfits73

Have a look at my document:


Clutter profile image
Clutter in reply to misfits73


200mcg daily.

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