How much T3/T4 should I take?: I've been looking... - Thyroid UK

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How much T3/T4 should I take?

Seashine10 profile image

I've been looking into obtaining Liothyronine (probably Tiromel 25 mcg) to supplement the Levothyroxine I currently take. Hypothyroidism runs in my family - I've been on T4 since I was 19 and my daughter since she was 11. Both of us can maintain our weight but struggle to lose it and both of us need to. It affects our self-confidence everyday and I'm desperate to find a solution. I'm also struggling with depression and I've read that T3 can help with that too. The only thing I'm unsure about is the amounts to take. I have been taking 137.5 mcg levothyroxine (averaged over 2 days) for the last year or more. My last results (29/09/21) were:

FT3 4.1 (4.0 - 6.6)

FT4 13.6 (no range given)

TSH 0.02 (0.34 - 5.6)

My GP wants to decrease my levo because my TSH is suppressed. I have many hypo symptoms. My Serum ferritin (33 ug/l) is apparently low but everything else is normal, including Vit D.

I'm thinking of starting on 1/4 of a 25 mcg T3 tablet twice a day for the first month then upping to 1/2 a tablet twice a day. I'm also thinking I should reduce the T4 to 100 mcg daily which is what my GP wants to do anyway.

Does anyone have any advice/suggestions?


43 Replies

Impossible to interpret your FT4 result without a range. But, if you are on 137.5 mcg, you either have an absorption problem or a conversion problem - impossible to know which without the FT4 range.

Starting on 12.5 mcg T3 might be a bit much for you. So, if I were you, I would start on just 1/4 tablet and increase by 1/4 tablet after two weeks. Only ever increase by 1/4 tablet at a time, but you can do so every two weeks. Start low and increase slowly is the rule, as with any other hormone. :)

BTW, your doctor is very ignorant for dosing by the TSH. You are only over-medicated if your FT3 is well over-range. And yours is a long way off that!

Seashine10 profile image
Seashine10 in reply to greygoose

Thanks for the advice re dosage.

I have been in battle with my GP for a few years over blood results! I tried arguing that my T3 was low but she still insists my Levo will have to be reduced if I have another suppressed TSH result. I had to request the dose be put up from 100 mcg (went to another GP in the practice!) because my arms were so painful - feels like bone pain maybe? Very deep, persistent aching. I just feel like nothing will get better for me and, more importantly, my daughter unless I do something else.

greygoose profile image
greygoose in reply to Seashine10

Well, the best thing would be to change doctors, if you can. This one is far too ignorant to ever make you well. In fact, she's a public menace! Think if it were me, I'd complain to the practice manager.

I really can't tell you if you need T3 or not, because of that lacking FT4 range - do you have any previous results from the same lab? But, you're right, you have to do something. :)

SlowDragon profile image

First step is to ALWAYS get FULL thyroid and vitamin testing results and ranges

Was test done as early as possible in morning before eating or drinking anything other than water and last dose levothyroxine 24 hours before test

You need to know range on Ft4 result

Ft3 obviously low

ESSENTIAL to improve all four vitamins to optimal …..ideally BEFORE adding T3

Please add actual results and ranges on vitamin D, folate and B12

What vitamin supplements are you currently taking

Ferritin is obviously far too low

Are you vegetarian or vegan

You ideally need full iron panel test for anaemia

Presumably you and your daughter have autoimmune thyroid disease also called Hashimoto’s

Have you had coeliac blood test done

Are you on absolutely strictly gluten free diet

Thanks for your reply.

Vit D was 124 nmol in Sep 21

I haven't had recent B12 or folate tests but both were within range last time and I regularly take a multivitamin which contains daily recommended dose 200% Vit D, 100% iron and enough B vitamins to turn my wee yellow! I also take a prescribed iron tablet but not regularly due to interaction with various other drugs and it being the lowest priority at the moment.

I'm not technically vegetarian or vegan but eat very little meat. I eat lots of veg, use soya or oat milk and prefer lentils and pulses to meat. I need to increase the protein in my diet as when I cook meat for the family I tend to mostly just have veg rather than replacing it properly.

I've never had any diagnosis more specific than hypothyroid but my daughter has Hashimoto's and as my Mum, 2 sisters and nephew are also all taking thyroxine I would assume autoimmune.

My GP said I'm not actually anaemic as my red blood cells are still ok. My last serum iron result was 19 umol/L (14-29) in Aug 2020, my serum ferritin was 67 ug/L at that point.

I've never been tested for coeliac disease and do not follow a gluten free diet.

SlowDragon profile image
SlowDragonAdministrator in reply to Seashine10

Suggest you consider getting FULL thyroid and vitamin testing done BEFORE considering adding T3

You will have to get use to doing FULL thyroid testing yourself regularly if adding T3

ALWAYS test as early as possible in morning before eating or drinking anything other than water and last dose levothyroxine 24 hours before test

Do you always get same brand levothyroxine at each prescription

Regular Soya not recommended for any one on levothyroxine

greygoose may pop by and can explain why

Most multivitamins not recommended on here…..most contain iodine not recommended for anyone with Hashimoto’s

Strongly recommend getting coeliac blood test done BEFORE trialing strictly gluten free diet

What other medications are you currently taking?

As others have said, taking almost any dose of T3 will suppress TSH…..and if GP is TSH obsessed they will want to reduce dose levothyroxine further….often inappropriately

greygoose profile image
greygoose in reply to Seashine10

Unfermented soy isn't recommended for anyone, it's not just those taking levo. Soy is a goitrogen, meaning that it impedes the uptake of iodine by the thyroid, causing a goitre - hence the name. True, you would have to ingest a hell of a lot of it to get to that point, but the thing with soy is that it also impedes the uptake of thyroid hormone by the cells. This means that you can have good levels in the the blood, but still have hypo symptoms because it's not getting into the cells.

It's not just iodine that makes multi-vits a bad idea, there are lots of other things wrong with them, too:

* If your multi contains iron, it will block the absorption of all the vitamins - you won't absorb a single one! Iron should be taken at least two hours away from any other supplement except vit C, which is necessary to aid absorption of iron, and protect the stomach.

* If your multi also contains calcium, the iron and calcium will bind together and you won't be able to absorb either of them.

* Multi's often contain things you shouldn't take or don't need : calcium, iodine, etc. These things should be tested before supplementing.

* Copper and zinc need to be kept balanced, but hypos are often high in one and low in the other - often low in zinc. So, both should be tested before supplementing. Taking either of them when you already high in it, will reduce the other and make you feel worse.

* Multi's often contain the cheapest, least absorbable form of the supplement : magnesium oxide, instead of magnesium citrate or one of the other good forms; cyanocobalamin instead of methylcobalamin; folic acid instead of methylfolate; etc. etc. etc. This is especially true of supermarket multis.

* Multi's do not contain enough of anything to help a true deficiency, even if you could absorb them.

* When taking several supplements, you should start them individually at two weekly intervals, not all at once as you would with a multi. Because, if you start them all at once, and something doesn't agree with you, you won't know which one it is and you'll be back to square one.

* Most supplements should be taken at least two hours away from thyroid hormone, but some - iron, vit D, magnesium and calcium (should you really need to take it) should be taken at least four hours away from thyroid hormone.

*Vit C should be taken 2 hours away from B12 because it affects how the body uses B12.

*Never take magnesium/zinc/calcium at the same time as they affect the absorption of each other.

*Take zinc and copper separately as zinc affects the absorption of copper, if you need to take both.

*Vits A/D/E/K are all fat soluble vitamins, and if taken together can compete for the source of fat. They are best taken away from each other.

* The magnesium you take - and just about everybody needs to take it - should be chosen according to what you want it to do:

Magnesium citrate: mild laxative, best for constipation.

Magnesium taurate: best for cardiovascular health.

Magnesium malate: best for fatigue – helps make ATP energy.

Magnesium glycinate: most bioavailable and absorbable form, non-laxative.

Magnesium chloride: for detoxing the cells and tissues, aids kidney function and can boost a sluggish metabolism.

Magnesium carbonate: good for people suffering with indigestion and acid reflux as it contains antacid properties.

Worst forms of magnesium: oxide, sulphate, glutamate and aspartate.

With a multivitamin, you are just throwing your money down the drain, at best, and doing actual harm at worst. Far better to get tested for vit D, vit B12, folate and ferritin, and build up your supplementation program based on the results. A vitamin or a mineral is only going to help you if you need it, anyway. More of something you don’t need is not better, it's either pointless or even dangerous, as with iodine, calcium, iron or vit D. :)

Sorry if that's a bit long-winded, but I wanted to get it all down in one place. :)

janeroar profile image
janeroar in reply to greygoose

Hi greygoose i supplement zinc that has a small amount of copper in: Jarrow Formulas Zinc Balance Capsules, 15 mg, 100-Count

Should I get tested before continuing with this formula? I thought zinc level was hard to test?

Thanks in advance

greygoose profile image
greygoose in reply to janeroar

I'm not aware of any difficulty testing for zinc. Ask your doctor and see what he says. Or, at least test for copper. If your copper his high, your zinc will likely be low. That supplement is not really for someone with a deficiency in either. It's another worried-well type supplement.

janeroar profile image
janeroar in reply to greygoose

Thanks for this but do you mean it’s not a supplement to worry about?

greygoose profile image
greygoose in reply to janeroar

I mean it's not a supplement a hypo should be taking.

janeroar profile image
janeroar in reply to greygoose

Hi greygoose Do you mean copper or zinc isn’t a supplement hypos should be taking? I very much need zinc. When I don’t take it I get white spots on my nails and when I do take it they go away and I seem to be much more resistant to colds. I use zinc lozenges too when I feel a cold coming on and they are very effective (and there’s q a lot of research proving this).

As for copper, my understanding is that vitamin C which I take in liposomal form ( so it’s a high dose) can deplete copper levels. Low levels of copper is also implicated in causing thyroid issues.

greygoose profile image
greygoose in reply to janeroar

I explained above:

* Copper and zinc need to be kept balanced, but hypos are often high in one and low in the other - often low in zinc. So, both should be tested before supplementing. Taking either of them when you already high in it, will reduce the other and make you feel worse.

So, sounds as if you're one of those who are low in zinc - like me - in which case you need to take zinc, but not copper. Your copper will already be high - the lower the zinc, the higher the copper. Taking more copper on top is not a good idea. So, if I were you, I would get a supplement with just zinc, nothing else. :)

janeroar profile image
janeroar in reply to greygoose

Thanks for clarifying greygoose !

greygoose profile image
greygoose in reply to janeroar

You're welcome. :)

janeroar profile image
janeroar in reply to greygoose

greygoose another question. Is there a company that charges a reasonable amount for testing zinc and copper? Thank you

greygoose profile image
greygoose in reply to janeroar

I'm afraid I have no idea. But you might find something here:

janeroar profile image
janeroar in reply to greygoose

👍🏼 Thanks

T3 liothyronine tends to suppress TSH so be prepared for more difficult conversations with your GP as your TSH is not likely to rise to within range on combo.

Seashine10 profile image
Seashine10 in reply to Lalatoot

Ah well! She's used to me arguing with her. I might avoid TFTs for a bit!

SeasideSusie profile image


Your Ferritin level is very close to iron deficiency which is diagnosed when level is <30ug/L according to NICE:

Interpreting ferritin levels

In all people, a serum ferritin level of less than 30 micrograms/L confirms the diagnosis of iron deficiency.

You really need an iron panel which tests serum iron, transferrin saturation, total iron binding capacity as well as Ferritin. This will determine iron deficiency. You should also have a full blood count to see if you have anaemia.

What are the levels of the "normal" results?

All key nutrients need to be optimal for any thyroid hormone to work properly, and some experts say Ferritin optimal level for thyroid function is 90-110ug.

So the first thing to do is ensure all nutrients are at optimal levels before considering adding T3. These are:

Vit D - 100-150nmol (or 40-60ng/ml).

B12 - minimum 550pg/ml preferably 900-1,000, for Total B12 or for Active B12 over 100.

Folate - at least half way through range

Ferritin - half way through range or 90-110ug /L.

Without a range for your FT4 we cannot work out whether or not you are a poor converter so we don't know if you need T3. The ranges we usually see here are 7-17, 9-19, 11-23, 12-22, so your FT4 could be low in range as well as our FT4 so it's essential to know all ranges.

Also, T3 is not a weight loss drug.

Thanks for your reply.

My ferritin is up from 20 mg/ul in May 2021 and I take iron in a multivitamin regularly and also as a stand-alone occasionally (I know I need to improve this).

Vit D was 124 nmol in Sep 21

I haven't had recent B12 or folate tests but both were within range last time and I regularly take a multivitamin which contains daily recommended dose 200% Vit D, 100% iron and enough B vitamins to turn my wee yellow!

I've gone back through years of TFT results on the NHS app and unfortunately the reference range for FT4 is never mentioned. A bit of googling has found the current range to be 12-22 within the county and I know that a result I had below 10 was considered too low. I will try to find out on Tuesday.

I do realise T3 is not a weight loss drug but my daughter and I have reasonably decent diets and I swim a couple of miles a week and walk alot but still really struggle to lose weight so I'm hopeful it might be the missing link that helps. We are also both low on energy, get brain fog, have dry skin and I have brittle hair and nails and hair loss and my daughter gets really cold. The weight thing is a big deal for me but I'd really like to just generally feel better as well. I am struggling with depression and spent last week in a mental health crisis house.

SlowDragon profile image
SlowDragonAdministrator in reply to Seashine10

Perhaps Testing for common Dio2 gene variation too

If you test positive it can help get T3 prescribed on NHS

Roughly where in U.K. are you?

Email Thyroid UK for list of recommend thyroid specialist endocrinologists...who will prescribe T3

NHS and Private

How much do you weigh in kilo

How much levothyroxine are you currently taking

Guidelines on dose levothyroxine by weight is approx 1.6mcg levothyroxine per kilo of your weight per day

I'm in Somerset in the South West.

I weigh far too much: 128 kg :-( It upsets me every day. I was in a mental health crisis house last week and starved myself, eating nothing for the first 48 hours and then averaging 600 calories after that (without deducting for swimming and hill climbing!). I lost a grand total of 1kg which was quickly regained as soon as I started eating sensibly. Most people could lose the 1kg on a 1400 calorie diet, probably more at my weight. My daughter doesn't weigh anything like that but she has the same problem losing weight (as does my mum).

I've also just read that hirsutism can be attributed to taking LT4 and reduced by LT3 so there's another reason to try this!

I take 137.5 mcg (averaged) L-T4 which equates to 1.05 mcg/kg per day. My GP wants to reduce it because my TSH is suppressed. My FT3 is only 4.1 (4-6.6).

SlowDragon profile image
SlowDragonAdministrator in reply to Seashine10

Guidelines on dose levothyroxine by weight suggests you should be on around 200mcg levothyroxine per day

Email Thyroid UK for list of recommended thyroid specialist endocrinologists who will prescribe T3

NHS and Private

Thyroid U.K. Office opens tomorrow

Meanwhile working on improving low vitamin levels and trialing strictly gluten free diet

Excess hair suggests PCOS ..extremely common with autoimmune thyroid disease

SlowDragon profile image
SlowDragonAdministrator in reply to Seashine10

There are two types of consultant who can prescribe T3

A thyroid specialist endocrinologist

But also a psychiatrist can prescribe T3 …..low Ft3 and treatment resistant depression are linked

Also SD, an oncologist after TT for thyroid cancer. It’s amazing how many people are looked after by other - ologists after thyroid cancer.

Me1157 profile image
Me1157 in reply to SlowDragon

In order to get this list you have to join, which is a good thing. I couldn't get access to the list unless I paid for it....which the funds help the members. BTY was worth it's weight in gold.

SlowDragon profile image
SlowDragonAdministrator in reply to Me1157

The specialist recommended endocrinologist list is emailed direct to you on request

The private doctor list comes as part of membership pack

2 different lists

I am sorry you are feeling rubbish! I wonder if you have a pituitary problem as your TSH is unusually low with low T3 and T4?

If I were you I would not go down the route of self sourcing T3 ( yet!) and would ask to see a thyroid friendly endocrinologist. I think you need further tests to see what is going on and if you self treat it would muddy the water at the moment.

Does your daughter have a similar picture of thyroid results with low TSH/T3 and T4 ?

Oh, and if your GP does not help, find another one!

Good luck.

The members on here certainly know way more about thyroid than most. I have hashimotos and I'm a poor converter from T4 to T3 and my TSH has always been near 0. My GP believes me when I say I still have all the symptoms of hypo, but thinks the blood results are within normal range. He sent me to an endo recently .....who according to her I have fibromyalgia...and my thyroid is fine....Even though I had RAI ( drank DR perscribed radio active iodine), treatment in 1979 and have to be on thyroid meds for the rest of my life. FYI - there isn't any reliabale blood tests for fobromyalgia... I think that's their catch all when they simply don't know..but, there is a full thyroid panel to help find out what truly is going on with the thyroid. Many endocrinologists adhere to the current trend that the TSH is the only result needed to decide what your medication dose should be...and that isn't right at all. I agree you need to start testing your blood yourself by doing a full thyroid panel with antibodies every few months and tweak your meds accordingly.....When you put your results on here and the members will help you as they have helped me. I'm still tweaking my medication to get it right. I found a good thyroid doctor from joining It willl cost you money and ppl in the UK aren't used to paying for Doctors, bloodwork and meds.....but in order to be well and get this under need too take control of your health...... it's your body and you need to be living your best life and not struggling through each day. I have been blanced before and felt great and will be again! Good luck on your journey.

Sorry to hear you’re having such a rough journey. I hear echoes of my own as I was reading your post. I had similar experience of suppressed TSH, low T3 and in my case elevated T4 and all the hypo symptoms. I foolishly had agreed to drop dose and have put on a stone and a half in the last year and had points where my mood was so low I had thoughts of self harm and fleeting suicidal thoughts.

HOWEVER I finally took control (like it sounds you are doing) and with some invaluable support from this forum located a private endo who I have been working with to sort this mess out. In my case we have gone down the road of ERFA (natural desiccated thyroid) which is a mix of T3 and T4.

It has been a slow journey, but even on the ‘same’ dose equivalent my T4 halved so only just scraped into bottom of the range, rather than flying out the top and my TSH rose to within normal levels for the first time in 11years. Endo conceded I did indeed perhaps need the higher dose, mood has improved dramatically, although weight hasn’t yet. I’m going to do a blood test this week and suspect I will need perhaps one more dose increase to hit the sweet spot (ironically the equivalent dose of levothyroxine I was on for years when I felt well, but due to Levothyroxine impact on TSH and T4 always freaked the doctors out!)

Things I’ve learnt:

Have confidence in your own knowledge of your body

Shop around for an endo you trust and can work with (happy to PM you the one I see. He works from Bristol and Weston-super-mare)

Source your own blood tests - list on thyroid U.K. website. Range of prices. Discount codes available through them. You can get one done for as little as £23. Advantages of this you really know and can keep track of what is going on and can argue point with GP/NHS endo (who I was also under) when they start getting twitchy about why you have made your treatment choices - effectively play them at their own game.

Finally take it slowly. It’s easier to monitor impact if you are making small changes. For example I substituted part of my levothyroxine for some ERFA, then swapped out a bit more. I’m still on a mix of the two medications atm, and may find long term some type of hybrid arrangement using a mix works best for me.

Good luck with your journey. Wish me luck with my ongoing weight loss struggles……

Hello, I have read your reply with great interest, and would be very grateful if you could send me a private message with details of your endocrinologist near to Bristol. Although my present consultant will prescribe T3 he is hellbent on reducing the doses of both T4 and T3 making me feel rubbishThank you. Ann

Definitely wishing you luck with weight loss. I want to scream at people who say eat less, exercise more! I know that idea makes total sense but it doesn't seem to work that way. :-(

Please could you PM the name of the endo? I might be able to get referred there as it's the same county. Thanks. 😊

Id start on 1/4 tablet of lio with your Levo first thing for a week before adding in a second 1/4 6-8 hours later. I’d be tempted to stick with that for four weeks before retesting. I wouldn’t reduce your Levo at all for now.

Sorry to hear about your problems. Eventually I found a GP who referred me to an endocrinologist who understands about T3 and prescribed it for me on NHS. Do hope you can do the same.

I don't know how old you are, but I would also consider the menopause conjunction with your thyroid symptoms; same symptoms different treatment

Wow, thank you, so much knowledge here and things I hadn't considered!

I have just managed to sleep through the entire day which is really frustrating as I had plenty to do.

I think I have sorted vitamins out enough to be able to exclude them as the main issue. Increases have made a difference to my skin but little else.

I'm 43 so perimenopause is definitely a consideration but the only thing that has worsened has been depression and there are unfortunately multiple reasons to explain that even if menopause is a contributing factor.

2 weeks ago I was convinced I had made it through my last day on the mortal plane. Waking up on the Tuesday was 1 of the most distressing experiences ever but if I have to keep going then I have to try to take some control back. So no more waiting around, I'm going to order the T3 and start on 1/4 tablet for a week without adjusting my T4. I started writing it up a bit like an experiment last night and that is how I'm going to approach this.

helbell profile image
helbell in reply to Seashine10

I've nothing to add to all the great advice here but I do know that I'm horribly depressed when my FT3 is on the floor of the range, as well as a host of other awful symptoms. Plus, my weight and bp rise. If your T4 range is 12-22, I'm in North Somerset, then my numbers are very similar to yours when my T3 is down. My TSH has always been low despite low T3 and T4 - even at diagnosis, when my free ts were under range, my TSH was only 4.8 I had to beg for Fts to eventually be included as I already suspected hypothyroidism. My gp diagnosed fibromyalgia - a classic catch all, with depression and anxiety. My ratio has never been remarked on and my gp continues go by my TSH. But I now self test and dose. Not ideal but left to my gp I'd be seriously ill. I also saw an endo from Bristol that visits Weston. He listened and was interested in clinical signs, as opposed to numbers, and asked my surgery to test T3 in future...that went down like the proverbial in a helmet, but it least it covered my non compliant back for a while. Time for another appointment me thinks. Keep the faith, you're already finding out for yourself which is a huge part of the journey. Good luck.

T3 is four times as strong as T4. So, if you reduce your T4 by 20 mcg you would take 5 mcg's of T3. That would be a good place to start. I take 2.5 T3 three times a day. If I take 7.5 all at once it makes me too hyper. You don't have to worry about taking T3 on an empty stomach or at the same time as your T4.

helvella profile image
helvellaAdministrator in reply to playtime2

We need to be careful when we say that T3 is any particular proportion stronger than T4.

We can't take a ratio off the shelf and expect it to apply to everyone, in all circumstances.

playtime2 profile image
playtime2 in reply to helvella

Yes and no. Having a standard acceptable conversion ratio is useful as a starting point. All of us, that take things into our own hands, as I do, then tweek things. This is also true of our total dose amount being based on our weight. We have to start somewhere. The ratio of four times as strong, is a good place to start.

I'm working on the basis that I'm under-treated at the moment. Based on weight, I should be on 200 mcg, I'm actually on 137.5 mcg. I might reduce to 125 for easy maths and to save a few 25s to play with dosing as I adjust to the Lio.

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