Under active thyroid : I was diagnosed with under... - Thyroid UK

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Under active thyroid


I was diagnosed with under active thyroid and ended up taking 200 thyroxine a day ,but felt absolutely no benefit from it .I struggle to loose weight when in the past so long as I stuck to a plan I managed to do it .Recently I went on holiday and ran out of tablets and after coming home I left it for a month before going to the doctors for blood tests the result of which I got to day . T4 6.3 and TSH 59 , the doctor has recommended that I start on 100 and go back in a fortnight for fresh tests .I'm male 72 years and 20 plus stone ,any thoughts please .Thank you

2 Replies

You need your FT4 and your FT3 tested at the same time, to see how well you are converting your levo. If 200 mcg levo didn't make you feel better, then the odds are, it isn't converting to sufficient T3, the active hormone.

You could ask your doctor to test the FT3, but even if he agrees, the lab will probably refuse, so you might want to get the test done privately. :)


If 200mcg Levothyroxine was not helping then likely to have poor gut absorption or low vitamins

Do you have any gut issues?

For full Thyroid evaluation you need TSH, FT4, FT3 plus TPO and TG thyroid antibodies and also very important to test vitamin D, folate, ferritin and B12

Bloods will need retesting 6-8 weeks after being on constant 100mcg dose. Likely that dose will need increasing in 25mcg steps until TSH is around one and FT4 towards top of range and FT3 at least half way in range

Low vitamins are EXTREMELY common. Ask GP to test vitamin D, folate, B12 and ferritin now, plus both TPO and TG thyroid antibodies

Private tests are available. Thousands on here forced to do this as NHS often refuses to test FT3 or antibodies or vitamins


Medichecks Thyroid plus ultra vitamin or Blue Horizon Thyroid plus eleven are the most popular choice. DIY finger prick test or option to pay extra for private blood draw. Both companies often have money off offers.

All thyroid tests should ideally be done as early as possible in morning and fasting. When on Levothyroxine, take last dose 24 hours prior to test, and take next dose straight after test. This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, GP will be unaware)

If antibodies are high this is Hashimoto's, (also known by medics here in UK more commonly as autoimmune thyroid disease).

About 90% of all hypothyroidism in Uk is due to Hashimoto's. Low vitamins are especially common with Hashimoto's. Food intolerances are very common too, especially gluten. So it's important to get TPO and TG thyroid antibodies tested at least once .

Link about thyroid blood tests


Link about antibodies and Hashimoto's



List of hypothyroid symptoms


Always take Levo on empty stomach and then nothing apart from water for at least an hour after. Many take early morning, on waking, but it may be more convenient and possibly more effective taken at bedtime.


Other medication at least 2 hours away, some like iron, calcium, vitamin D or magnesium at least four hours away from Levothyroxine

Many people find Levothyroxine brands are not interchangeable. Once you find a brand that suits you, best to make sure to only get that one at each prescription. Watch out for brand change when dose is increased or at repeat prescription. Many patients do NOT get on well with Teva brand of Levothyroxine. Though it is the only one for lactose intolerant patients

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