Thyroid UK
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How much is too much Levothyroxine?

TPO antibodies 2000 (<34)

TSH 4.70 (0.27 - 4.20)

FT3 3.2 (3.1 - 6.8)

FT4 14.8 (12 - 22)

Hello I am new and I take 175mcg Levothyroxine. GP and endo won't increase because I am said to be on a high enough dose. So am I on the upper limit of Levothyroxine? Am I doing something wrong?

Thanks for reading

23 Replies


There is no upper limit to how much Levothyroxine can be prescribed. The usual maintenance dose is 100–200 micrograms once daily according to NICE but members on the forum have been prescribed between 300mcg - 500mcg.

Your endo should prescribe 200mcg and retest in 6-8 weeks. If TSH is higher than 0.27 - 1.0 a further dose increase to 225mcg should be prescribed.

The goal of Levothyroxine is to restore the patient to euthyroid status. For most patients that will be when TSH is 0.27 - 1.0 with FT4 in the upper range. FT4 needs to be in the upper range in order that sufficient T3 is converted. Read Treatment Options in Email if you would like a copy of the Pulse article to show your endo and GP.


Thanks my GP has said she won't increase because I am aiming to be pregnant and she thinks I will miscarry on 200mcg



You may not be able to conceive with TSH 4.7 and if you do the likelihood of miscarriage is high when TSH is >3.0.

The BTA recommends the TSH of women planning conception should be in the low-normal range 0.4 - 2.5.

Dose is usually increased by 25-50mcg when pregnancy is confirmed to ensure good foetal development. NICE recommends that women planning conception should be referred to endocrinology for management.

Management of primary hypothyroidism: statement by the British Thyroid Association Executive Committee

13. The serum TSH reference range in pregnancy is 0·4–2·5 mU/l in the first trimester and 0·4–3·0 mU/l in the second and third trimesters or should be based on the trimester-specific reference range for the population if available. These reference ranges should be achieved where possible with appropriate doses of L-T4 preconception and most importantly in the first trimester (1/++0). L-T4/L-T3 combination therapy is not recommended in pregnancy (1/+00).


Your GP is not adhering to guidelines as TSH should be under 2 to ensure conception and successful pregnancy.


Everyone is different and people need different amounts of levothryoxine. There isn't an upper limit as such. Levothyroxine can also vary in strength which may affect how much a person needs to take. I have been on 250mcgs at one point only to find out that the levothyroxine was faulty and that was why I needed so much! Most people take between 100 and 200mcgs and 125 to 200mcg seems quite a normal dose if you read people's accounts on this forum.

TSH 4.70 (0.27 - 4.20) TSH is over range. The top of the lab range here is 4.20 and your result is 4.70, showing clearly you do not have enough thyroid hormone. Most people don't feel well until TSH is 1 or a little lower.

FT3 3.2 (3.1 - 6.8) FT3 is very low in range indicating that you do not have enough FT4 for your body to utilise and turn into T3. Your body needs T3 to function effectively. FT3 is best in the top third of the range.

FT4 14.8 (12 - 22) Your FT4 is low in range and is best in the top third of the range.

You would benefit from a dose increase of 25mcg and then retest in 6 weeks time and adjust dose and retest and so on until your TSH reaches 1 or a little lower.

Your TPO antibodies are elevated showing that you have autoimmune thyroid disease otherwise known as Hashimotos.

It's possible you have absorption problems as many people with Hashimotos do. It's worth getting your GP to test vitamin levels. B12, folate, ferritin and vitamin D. All can be low in people witth thyroid disease and prevent efficient conversion of T4 to T3.

If your Endo is concerned about increasing your dose of levvothyroxine he/she would do well to look into any possible absorbtion issues rather than refusing to increase your dose of levothyroxine. Do you have symptoms and if so, what kind?

Just one more thing to check, are you taking your levothyroxine with a full glass of water on an empty stomach and then waiting one hour before eating or drinking anything except for water and are you taking any other medicines at least 4 hours after taking thyroid meds?

1 like

Thanks my GP has said she won't increase because I am aiming to be pregnant and she thinks I will miscarry on 200mcg.

Symptoms are tiredness, hard stool, cold sensitivity, puffy eyes, memory loss, tinnitus, dizziness, hair loss, weight gain, loss of appetite, sugar cravings, heavy periods, pins and needles

I take my levothyroxine with a full glass of water on an empty stomach waiting 4 hours before eating or drinking anything and I take no other medications



There's really no need to wait longer than an hour after taking Levothyroxine to eat and drink.

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, magnesium and oestrogen.


These are recent guidelines for pregnancy. Could you take a copy to your GP and discuss?

Pregnancy guidelines

American Thyroid Association 2017 pregnancy guidelines for thyroid disease more up to date than UK guidelines which are at least 2 years old.


Thanks I tried to discuss with my GP but she said "I have hypothyroidism so I would know how much is too much for you" and that shut me up. :(


Just because her own hypothyroidism is controlled on a low amount doesn't mean everyone else’s is. If you are over range then you are under medicated - it is worth asking her what the ranges are for if she is ignoring them.

Unfortunately if the information posted by Clutter doesn't change the GP's mind then you need to be referred to a fertility specialist - which you are likely to have to do privately. The only option you have if you can't afford to do that is to change GP practice to one who isn't so stubborn but that will be like looking for a needle in a haystack.

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See another GP. She won't keep you well or help you have a successful pregnancy - and make a formal complaint about her not adhering to guidelines for women trying to conceive. Too much ego, not enough empathy.


Please remember Thyroid Disease is genetic and the chances of it affecting your child in many different ways is pretty high


Clearly you're not satisfied with that response so you need to return and spell out what the guidelines say and state that you want to be treated according to the guidelines. You can point out that the British Thyroid Association, which is the one that all the Thyroid surgeons in the UK subscribe to cite the ATA guidelines on their website as a reliable resource for Doctors and patients.



How recent do vitamin and mineral levels need to be? I had some checked in Dec 2017?


They will be in date from December. Some of your symptoms could be attributed to low vitamin levels such as tinnitis which is a symptom of low B12. Hair loss may be low iron levels and possibly low mineral levels too. Pins and needles could be low B12 or folate. Please do post vitamin levels.


Vitamin B12 226 (190 - 900) awaiting B12 injections for 4 months

Folate 2.1 (2.5 - 19.5) can't start folic acid until first B12 injection has been done

Ferritin 22 (15 - 150) taking 1 iron tablet for iron anaemia

Vitamin D total 55.7 (50 - 75 vitamin D suboptimal. Advise on safe sun exposure and diet.) taking 6000iu vit D oral spray. 800iu prescribed to me wasn't raising level at all.


B12, folate and ferritin are all too low and Vit D needs to be higher. Look at Seaside Susie Posts re supplements. Don't trust GP to provide you with correct amounts! Vit D they gave you was pathetic wouldn't raise the level ever.!




As you are trying for pregancy, you really don't want to get pregnant until you have adressed your low folate levels and you do need to increase your B12 levels first as they are low. Has your GP ruled out pernicious anaemia by checking for intrinsic factor antibodies?

Have you had B12 injections before or are you just starting? You really do need those B12 injections. Shouldn't they be every 3 months?

B12 The Guidelines Doctors follow

Clutter has given you good links and advice re pregancy guidelines in the UK.

You need to aim to increase vitamin D level to around 100nmol or mid-range. It looks like you are making good progress with supplementing now so hopefully your level will now rise.

You need to take magnesium and K2-MK7 with vitamin D3 in order to absorb the vitamin D effectively. Magnesium citrate is ok but there are other choices for magnesium.

Ferritin needs to be at least 70 or mid-range for thyroid hormone to function properly. YOu may need an increase of iron supplements so discuss with your GP.

Iron deficiency anaemia NICE guidelines

The importance of vitamins and thyroid function



Thanks never had intrinsic factor antibodies tested. I have had 1 injection for B12 so far and they are every 3 months.

Have been taking vit D 3000iu since March 2015


Post your B12 and folate results along with an outline of your thyroid condition and symptoms, low ferritin etc on the HealthUnlocked Pernicious Anaemia forum and ask their advice about what your GP should be doing. Really, it looks like you need further investigations to rule out pernicious anaemia.

B12 symptoms of deficiency

If you have pernicious anaemia it may be the cause of low absorption of levothyroxine. Increasing B12 levels as well as other vitmamins may help. As you have Hashimotos, you may need to go strictly gluten free. I'll tag SlowDragon who has good advice about how to improve gut function and hopefully you may get a response.


Well, I wouldn't try getting pregnant with those awful results. You really do need to see a new GP


Total TOSH

correctly treated TSH should be 1.0 or below

Freet4 around 19

Freet3 around 5.5

Have they bothered to test




Vit d3

My husband daughter were both on 350mcg levothyroxine but still not well until they switched to NDT


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