Thyroid UK

Sorry one more question. Magnesium

I am speaking to my GP tomorrow about my test results, I haven't sooner as I came down with a virus and lost my voice.

My TSH was 9 in May and by November had come down to 2.6, FT4 19 and FT3 5, on 50mg of levo. My results last week showed TSH had risen to 5.7, Ft4 17 and Ft3 still 5.

I was going to speak to my GP about increasing to 75mg but am a little concerned. I have been taking Biocare vitamin c powder every morning for about a month, as I read it helps with levo absorption. What I didn't realise was it contains magnesium which I have read can reduce the absorption of levo. THis is what I have been taking.... just 1 scoop rather than the 2 they recommend. I am confused as it says it's vitamin c from magensium ascorbate.

Should i hold off the increase in levo and stick to 50mg if this could have effected the levo absorption? or still go ahead with the increase? I do have a concern of over medicating as I have an anxiety disorder so over medicating and having anxiety as a symptom concerns me a little. I am feeling very tired and weak again so feel I need to increase but I thought I'd ask here first before I speak to my GP. I for now have stopped the vitamin c supplement. I was taking it within 2 hours of levo.

Thank you.


3 Replies


If you are going to take vitC with Levothyroxine it shouldn't have anything else in it which might interfere with absorption. You shouldn't hold off on increasing Levothyroxine to 75mcg. If 75mcg proves to be too much dose can be adjusted to 50/75mcg alternate days.


Thanks Clutter.


Googled a bit and it's magnesium hydroxide an antacid that as we know can interfere the absorption of levo.

Anyway was also mentioned as just magnesium that can interfere and suggested to leave at least two hours between magnesium and levo.

You could take your vitamin C a bit later? I can eat vitamin C at any time of day without any problems with sleeping. I often take rosehip powder with night snack just before going to sleep.


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