T4: Hi, have asked questions on this forum before... - Thyroid UK

Thyroid UK

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Hi, have asked questions on this forum before and hound replies helpful.

I take 175 mcgs thyroxine daily. I have felt very sloth like for a while and asked for blood tests. I received a phone call from the doctor's surgery saying the doctor wants me to reduce my meds to 150. I asked for the reading and told it was 15!!! I can only function reasonably well at 20. I asked receptionist to tell doctor I won't t reduce my meds and have made an appointment to see her. I am so disappointed as I thought, after my last visit, she had some understanding πŸ˜”. Any advice? Thank you

4 Replies


What level is 15 and what's the reference range?

To get a full picture you need TSH, FT4 and FT3 and see where the actual hormone levels lie (FT4 and FT3 are the thyroid hormones) before any reduction in dose is made.

Omadoll in reply to SeasideSusie

Thank you. Doctor only takes T4 result. This should be between 10 and 24 and my reading for that, is 15. I am going to surgery today to ask for a copy of all results so I can be better informed.

SeasideSusieAdministrator in reply to Omadoll


So your FT4 is 15 (10-24) which is 35% through it's range. You need to ask your doctor what is it about your low FT4 that suggests you need your Levo reduced. That's utterly crazy if he's basing it just on that.


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

Have you had vitamin levels tested recently?

Insist these are tested, plus FT3 (and thyroid antibodies if not been tested)

Just testing FT4 is completely inadequate and GP can't actually grasp the results either by look of it

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)

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.

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