What kind of symptoms can you have when startin... - Thyroid UK

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What kind of symptoms can you have when starting T3?

naturegirl3434 profile image

I have been on 5mcg T3 for 2 weeks now taken in two doses (7:30am and 4:30pm.) I know my T3 is really low and my T4 is on the low end.

TSH 45.90 (0.270-4.20) Free T4 0.827 (0.71-1.7) Free T3 1.49 (2.5-4.3)

Vitamin D 26 (30-100) waiting for b12, folate, ferritin, iron tests

I just lowered my T4 from 125mcg to 50mcg because when my Dr. raised it I went hyper when I have always been hypo. I had all the hyperthyroid symptoms when I was hyper. When they lowered the T4 most of them went away. Since adding the T3 some have returned such as heart palpitations, heat/cold intolerance, tremor, agitation, sore stiff neck and legs, exhaustion, brain fog, and I am super shaky. A lot of these symptoms we have when we are hypo too. It makes it so hard to figure out what's going on. Would it be safe to say that the symptoms are due to low T3 and T4 and it will just take time to even out? Has anyone else had a lot of symptoms when starting T3? Please share. Do symptoms seem to get worse before they get better? I was feeling good the first week and now I feel ill again. Thanks...

7 Replies

Did you drop the t4 at the same time as introducing the t3?

No, we lowered the T4 from 125mcg down to 50mcg over a two month period and then re-did labs. Then introduced low dose of T3.

Hi there,

That sounds like an incredibly delicate balancing act you're negotiating. I'm also on T4/T3 combination (currently 100 T4 + 15 T3) and following my last increase of 5mcg T3 I didn't feel too well for a couple of weeks. I don't think my symptoms were as significant as yours, but I experienced a worsening of brain fog, poor concentration, anxiety and a thumping heartbeat at times. It wasn't too bad but enough to make me question whether the dose was too high for me, and I considered dropping back down to the previous dose.

Then, after two weeks, those symptoms dissipated literally overnight, as though my body had got used to the increased dose and settled down. I don't know if the same could be true for you, and I'm not medically qualified to advise, just my experience. Also, just remembered something else that might be relevant - when I first introduced T3 I saw significant improvements in the first few weeks or so but then they faded and I started feeling the same as before. So a bit like the pattern you've described. I interpreted it as indicating that T3 was helping but the dose wasn't high enough, it just depends on the signals your body is giving you. The crossover in symptoms is so confusing.

Your TSH does seem extremely high, and thyroid hormones low, I'm not surprised you feel so unwell. I'm sorry I don't know if I've said anything helpful here at all! Just understand the struggle with finding the right balance and wanted to reach out. Do you have any way of accessing a supportive medical practitioner to check this out with? I really hope things improve for you very soon.

Thanks for your reply it was very helpful. I think I need to just up my dose of T3 very slowly.

So glad it helped, really wish you good luck with it.

When I re-read your post I thought of something else - your vitamin D level is very low and T3 can be hard to tolerate when key micronutrients are suboptimal. That might be a factor for you at the moment. If you don't have too long to wait for the other results it might be worth holding off an increase in T3 until you have them, and start supplementing where needed. It could help to make introducing T3 smoother for you.

How is your adrenal function?

Low levels of free cortisol can cause difficulty when raising thyroid hormone doses. I believe the symptoms are very similar to being overstimulated (feeling hyper).

Your levels of Free T4 and Free T3 suggest this as they are nowhere near being excessive.


Iron deficiency should also be ruled out


Thanks so much. I am working on getting the bloodwork for B12, folate, calcium, magnesium, cortisol, adrenaline, ferritin etc.

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