Solutions for brain fog when test results are g... - Thyroid UK

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Solutions for brain fog when test results are good


Hi there community

Last week I had a terrible period of brain fog (in addition to very low body temperatures c. 35.5 on waking for the past month). Together these inspired me to request a blood test to see if my levothyroxine dose needed to be increased. However my results were:

Tsh 0.05 (0.27-4.2)

Serum free T4 19.3 pmol/L (12-22)

I also had a full blood panel with no abnormal results

I’m confused by the tests and how I feel - as the tests may suggest I am over medicated, but the cool bbt and brain fog suggest under medicated?

As I am trying to conceive I’m keen to get my cycles regulated and to start ovulating (off the mini pill for almost 4 months now) so any advice or suggestions of things to ask the doctor would be appreciated.

Thanks in advance

11 Replies

Well, first of all, your results in no way suggest that you are over-medicated. The TSH is suppressed, yes, but the FT4 is well within range. And, as you are taking T4, not TSH, that is the more important reading.

However, just testing TSH and T4 doesn't tell the whole story. Although your FT4 is good, your FT3 could still be low, due to not converting very well. And, it's low T3 that causes symptoms, not T4 or TSH. So, without testing the FT3, you cannot know how well your are medicated.

@plokmijnuby I get brainfog and headaches from too much Levo /NDT. Maybe back the dose down a little. Also you need buckets of B12. I inject and keep in the 800-1200 ng/mL range.



Looking at previous posts you have Hashimoto’s

Just testing TSH and Ft4 is completely inadequate

Poor conversion of Ft4 to Ft3 is extremely common

EXTREMELY Important to regularly retest vitamin D, folate, ferritin and B12 too

What vitamin supplements are you currently taking?

Are you currently on strictly gluten free diet?

How much levothyroxine are you currently taking?

Do you always get same brand of levothyroxine?

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .

Last dose of Levothyroxine 24 hours prior to blood test. (taking delayed dose immediately after blood draw).

This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)

(If/when also on T3, make sure to take last third or half of daily dose 8-12 hours prior to test, even if this means adjusting time or splitting of dose day before test)

Is this how you do your tests?

Private tests are available as NHS currently rarely tests Ft3 or thyroid antibodies or all relevant vitamins

List of private testing options

Medichecks Thyroid plus ultra vitamin

Medichecks often have special offers, if order on Thursdays

Thriva Thyroid plus vitamins

Blue Horizon Thyroid Premium Gold includes vitamins

Hi Slowdragon

I will see what I can persuade the NHS to do but then buy an online test. The issue is finger prick blood collection doesn’t work and it is hard in the current lockdown to get to a phlebotomist.

Regarding vitamins I have the folic acid and Vit D but not tailored so will investigate improving these.

Not currently gluten free - I did that for the first 6 months but on the recommendation of a private Endo, a I generally have limited symptoms he suggested I don’t continue.

I currently take 100mcg and have always taken the same brand.

Test wise I fasted and didn’t take levo dose for 29 hours prior (11am test) as recommended on this forum 🙂

SlowDragonAdministrator in reply to plokmijnuby

So first step is to get full thyroid and vitamin testing see where you are

Brain fog can be due to gluten

Thanks slow dragon. I’ve gone gluten free now to help with that inflammation (and possibly fertility benefits). Also getting my fertility hormones tested when the nhs reopens fully. But in the meantime I will get a private blood test on t3 and vitamins :)

SlowDragonAdministrator in reply to plokmijnuby

You need to test TSH, Ft4 and Ft3 together...not just Ft3

Doctors just tested tsh and ft4 but I will get a test that does all of them so the bloods are aligned :)

The issue is finger prick blood collection doesn’t work

Can you explain why you think it doesn't work? It works for lots of people on the forum.

I tried it previously and despite following all advice and instructions my finger didnt produce sufficient droplets. Will look for more tips though cause I’m keen to get results soon rather than waiting for a phlebotomist appointment

SlowDragonAdministrator in reply to plokmijnuby

Follow SeasideSusie tips on how to do DIY finger prick test

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