Thyroid UK
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Vitamins and T4 help

Hi everyone,

I hope you are well. I have had a blood test as I am on my 4th week of 50microgram of levothyroxine, I need a little advice as I am concerned about my T4 levels.

My results are the following:

TSH (1.54) mIU/L 0.27 - 4.20

T4 (*24.1) pmol/L 12.00 - 22.00

IRON (20.19) umol/L 6.60 - 26.00

FERRITIN (18.7) ug/L 13.00 - 150.00

ACTIVE B12 (56.200) pmol/L 25.10 - 165.00

25 OH VITAMIN D (*29.5) nmol/L 50.00 - 200.00

I am going to start vitamin D supplement today but should I decrease my levo dosage? I am a little concerned my T4 is going out of range very quick? I have also arranged a private test so I can check my T3.

Thank you in advance.

5 Replies


Did you take FT4 before your blood test?

FT4 is a little over range but TSH isn't suppressed so you are not overmedicated. I wouldn't reduce dose unless you *feel* overmedicated. Slightly over range FT4 isn't necessarily a problem. Read Treatment Options in

Ferritin is very low in range but iron is good so you are not iron deficient.

Active B12 >35 is unlikely to be deficient.

VitD 29.5 is deficient. I would supplement 10,000iu D3 daily for 6 weeks and then reduce dose to 5,000iu alternate days and retest after 3 months. Take vitD 4 hours away from Levothyroxine.

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Hi Clutter,

That's great thank you : )

I don't think I will reduce the dose yet then, I will see how the vitD goes.

I have bought some Vitamin D spray today so hoping this helps.



If the spray is 3,000iu you'll need to use 3 x sprays daily for 6 weeks then 2 x sprays daily x 6 weeks and retest.

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Hi Clutter,

The spray is the 3000iu one, that's great, thanks!


Good idea to take some magnesium when on high dose vitamin D.

Plus vitamin K2 Mk7.

See this detailed supplements advice post

Active B12 is on low side. This link to St Thomas London hospital says anything under 70 is suspicious

You might want to consider taking daily sublingual B12 lozenge and/or good vitamin B complex

If you are taking vitamin B complex, or any supplements containing biotin, remember to stop these 3-5 days before any blood tests, as biotin can falsely affect test results

However only start one supplement at a time and wait 10-14 days before adding another. That way can assess response.

All thyroid tests should ideally be done as early as possible in morning and fasting and don't take Levo in the 24 hours prior to test. This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, GP will be unaware)

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