Thyroid UK
90,626 members105,007 posts

T3 question?

Hi, I am due to see a sympathetic Endo in a couple of weeks as my GP is concerned that I am not converting T4 correctly.

My recent test results are:

Tsh 0.04 (0.4-5)

Ft4 25.5 (12-22)

Ft3 3.02 (2.6-5.7)

I am currently taking 150 MCG Levothyroxin daily,

My GP and I have tried lowering the dose but the symptoms of hypothyroidism become so bad I can barely function. I am so fatigued. I am hoping that the Endo will prescribe T3 but I am also scared because of possible side effects. Is there anyone here who is successfully taking T3 Levothyroxin combo, and if so what brand of T3 were you prescribed. Also what amount of levo/T3 would I expect to be on given my results above.

I would be very grateful for any advice.

Wendy x

7 Replies

Wasimps, you aren't converting well because FT3 is low despite high FT4. Mercury Pharma Liothyronine is the T3 prescribed in the UK. T3 is 3 x stronger than Levothyroxine. As FT4 is over range it's likely Levothyroxine will be reduced by 25mcg for each 10mcg T3 added.

I'm prescribed Levothyroxine and T3. There were no adverse effects from adding T3 and benefits have been positive.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


I'm on uk t3 only as levo made me ill and I was not converting T4. I also take a small amount of armour thyroid and no side effects ,feel much better but don't take too much too soon. Up the amounts slowly, and it's a good idea to have your own blood pressure monitor as this can tell you if you have upped too much or not enough, for some people they feel better fairly quickly but others like me it's took over a year to get the amount right, and I'm still upping the amount . But just fine tuning now. Plus most people split there doses of t3, I take it 4 times a day and others are OK on one dose, you have to see what works best for you, be patient,


You have a very good GP as most go by tsh only. I do hope that the Endo is one who prescribed T3 because many don't.

I take it that your vitamin D and B12 are not deficient? and your ferritin? Folate? As deficiencies in these often go with hypothyroidism and have similar symptoms. For example your B12 needs to be above 500.

Let us know how you get on. Good luck.



How fortunate you are Wasimps to have a gp that takes this seriously.

My blood results are virtually the same as yours. My gp commented that 'as your T4 is going up your T3 is going down' yet he still wouldn't do anything!

My B12 is low (284 with a range of 190-900) so we're working on that at the moment. It's an uphill battle though.

Keep us posted as to how you get on with the endo xx


Wow, that is a lot of levo. The Abbott recommendation for T4-only is 1.7mcg/kg body weight. If you go on T3, you should get your T4 dose down, probably. Your FT3 should be at LEAST mid-range (4.1), but since it isn't, that is probably your problem.

I take a T3+T4=15+75mcg combination daily, one dose at bedtime. Works very well. I use brand Cytomel.

To get your dose set correctly, start with the Abbott T4-only recommendation. Then, lower your T4 dose and add T3 in accordance with a T3 power factor of 3-4. When you lower T4, remember that its half-life is long so you should wait 3-7 days before adding T3 to avoid hyper. Keep in mind that your T3:T4 ratio should probably be between 1:4 (like NDT) and 1:10. I am at 1:5 and that works well for me. Of course these are only guidelines, you results may differ, blah blah.

My clue on T4 was that my T4-only full replacement dose is around 130mcg, but I could only get T4 up to about 88mcg, and TSH down to 4. If I attempted to dose T4 higher, I would feel hyper and generally unwell. Adding in T3 was the path to Nirvana. That brought my TSH down to 0.5 and my FT3 up to mid-range.

1 like

I realise that I'm very lucky to have such a great GP, he told me that this endo has prescribed T3 quite a few times so that is why he requested him for my appointment. My ferritin level was low but after taking two supplements for the last few weeks they have risen to 1025 which my doctor says is around the optimum level for a hypothyroid sufferer, all my other levels came back as normal. Another question I have is how do I find out if my hypothyroidism is hashimotos? My Dad's sister was hypothyroid, but I am not sure if it's a hereditary illness? X


Hashi's is diagnosed by taking the TPOAb (Thyroid Peroxidase antibodies) and TGAb (Thyroglobulin antibodies) tests. Even GPs should routinely do those on hypothyroid patients, but they don't. You will be given a test result and some range from zero to X; if you are in that 0-X range, the System will tell you that you don't have Hashi's. My position is that any non-zero result is suspect and you should try to find out what is causing a non-zero result.

1 like

You may also like...