How long do b12 supplements take to kick in? - Thyroid UK

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How long do b12 supplements take to kick in?


I was previously taking Solgar's sublingual methococobalin (sorry, probably spelt wrong) and remember it making me feel a lot better with my brain fog, memory etc, but it didn't have any effect on my hair (still falling out unfortunately). After it ran out after 60 days there was a period of a month or two where I forgot to get some more, and I ended up getting Jarrow's methococobalin. Has anyone had this brand before? I'm taking one every day but am not feeling the benefit and wondering if I i should go back to Solgar . I can't remember off the top of my head but I think my last b12 result was around 100.


10 Replies

Are you sure the two things you are comparing are the same dose? Both the Solgar and the Jarrow methylcobalamin come in 1000mcg and 5000mcg doses.

I looked at your previous post :

and your B12 was given as :

B12 level 206 (191-663)

If you aren't getting any benefit from the Jarrow B12 then I would be suspicious that you had pernicious anaemia (PA) and are unable to absorb B12 from the gut. I think you should re-read the answers you got to your last post - PA is mentioned and so are some other tests you should be asking for.

I posted some information on the need for zinc with hypothyroid hair loss. Something to consider. Hair didn't grow back with optimal thyroid replacement just with added zinc.

milkwoman in reply to gabkad

It has to be the correct form of zinc (I read the study you posted). The correct form is Zinc Sulfate, 220 mg (yields 50 mg of elemental zinc), taken twice daily. I have found zinc sulfate on Amazon but actually found the best pricing for it (same brands) on medical supply sites.

I'm just starting this zinc supplementation (hoping my eyelashes/eyebrows regrow) along with Ferritin, Biotin, evening primrose oil, Vit D3 (5000 IU), Betaine HCL and BioSil. I seem to have absorption issues due to hypo (possibly Hashi's ...getting my antibodies tested for this).


Is the B12 you are taking sublingual as most of us have stomach issues with hypo and can have difficulties absorbing B12 anyway so sublingual is best. I have just started trying Zinc now as well, re hair loss.

If you've not had a test for PA, you should request one as it is a very serious condition left untreated. I know as my Mother died due to untreated PA.

I take Jarrows 5000mcg sublingual and it boosted my B12 nicely, I haven't taken Solgar but if you felt it was better for you then, just check the strength. Your B12 is terribly low, especially if you are taking a supplement. Like the others say, you need to get checked out for pernicious anaemia. Do you have a family history of PA - what does your GP say about your B12 being so low? I'm imagining it must be below range.

Three months ago my husband started taking sublingual methylcobalamin. He has found Solgar 1000mcg much more effective than Jarrows 5000mcg, which are harder and take a long time to dissolve under the tongue. He thought the higher dose Jarrows would be even better. It ain't necessarily so! He's now back on the Solgar.

Thanks for your answers everyone. Hillwoman... I've found the same, I usually chew the jarrows because I get bored waiting for them to dissolve! I will ask about the low b12 but I think it's still in the "normal" range so it's just been brushed off before, but I'll ask again, and will definitely ask about pernicious anaemia and look into zinc.

Does anyone have a recommended brand for zinc?

Hi There

Just noticed your post. My symptoms improved enormously when I started to take the sublingual methyl on an empty stomach and let them dissolve under tongue as they need to enter through the mucus membranes of the mouth. Via the stomach is no good if you are not absorbing at the moment.

Solved most symptoms such as brain fog, palpitations, tremors, eye pain and fatigue within about 6 weeks. Went from 1000mcg to 2000mcg to 5000mcg lately, as I have neuro symptoms that have not gone yet.

Note I don't believe I have PA, I think my problems stem from a low B12 diet and low Vit D affecting absorption. I am working to bring up by Vit D and praying for sunshine!

Blessings and good health



Your 100 serum B12 is far too low! Have you tried to get B12 injections from your doctor? The big problem hypothyroid patients have is absorbing Vitamin B12 through the stomach wall. Injections bypass this process by injecting the B12 directly into your blood stream. You could also try sub lingual tablets or drops which are placed under the tongue and are absorbed there. In New Zealand where I live, there is a sublingual drop product manufactured by 'Clinicians' that I use. I have 3 monthly injections as well. My initial Lab result was 85. Apparently the bottom 'safe' range used by my laboratory (172) is still far too low!

Hi Kate

I was taking the Jarrows sublingual, first 5000mcg daily which within 24 hours completely banished my spaced out feelings on NDT. However, the symptoms returned again and I increased to 10,000mcg which helped again, but over the months my health deteriorated (long story). I have and am having a hell of a battle with my GP who insists my serum levels are ok (even though I was taking sublingual B12 when I had the blood tests). I was diagnosed with MS and have been debating with him as to whether this was a misdiagnosis). I thought that Jarrows were a good make and interested to read your post, my homeopath doctor uses a lot of Solgar supplements so I guess they must be well thought of. The Jarrows do take forever to dissolve, especially 2 of the big ones!

It seems the B12 issue is as badly treated in the UK as thyroid issues and it is a devil of a job to get the right diagnosis, yet alone the right treatment. I am now self injecting thanks to my private doctor, only been doing this for 5 days but today I feel like my fatigue might be improving slightly.

Good luck


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