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Pernicious Anaemia Society
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B12 sublingual

Hi have been mostly vegan for about 10 years, so thought I needed b12 because I was very fatigued and loss of interest in anything. Started the b12 6 days ago and I’m feeling very hot, feeling down and cry very easy. Could it be the b12? 😩

11 Replies

Hi Health_hunter being vegan may well be the cause of your "B12 deficiency symptoms" as the only natural source of B12 is by eating animal products.

Have you actually had your serum B12 level tested to confirm that you are deficient?

It is not uncommon for some symptoms to "get worse before the get better" once supplementation starts as the B12 begins to repair any damage done to the nerve endings caused by the deficiency.

It's early days yet and hopefully you will see some improvement soon.

I wish you well


What dose are you taking? Sublinguals tend to be 1000mcg

If you are vegan and your deficiency is dietary then you really don't need the sort of doses that you get from high dose sublinguals - doses of around 25-50mcg for a short space of time followed by a supermarket supplement would be sufficient. Very high dose tablets in the absence of an absorption problem may actually have pushed your serum B12 levels up above normal range. In some people this can result in a reaction that stops the B12 in your blood from getting in to your cells leaving you deficient at the cell level.

I would suggest that you stop taking them and see if that results in any improvement - though it may take a while for levels to reduce again.

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I am a vegetarian (since I am born, I am 31 now), I have a healthy diet that includes dairies and eggs, and I now have a strong B12 deficiency following pregnancies (5 years ago and 1 year ago).

I was diagnosed fibromyalgia a year ago but not satisfied with this diagnostic I decided to test B12 after months of muscular aches, back pain, joint pain, fatigue, anxiety, even hallucinations, etc.

I recently got the results pointing out a strong B12 deficiency (138 ng/l, normal is above 180 ng/l).

I read all scientific papers to see what I should do, and all say the same: one should take between 1000 and 2000 mcg daily orally for a month (or more if there are still symptoms). Then if you are vegan you must complement (2 x 1000 mcg per week or 50 mcg daily).

I started to take 2000 mcg daily 6 days ago (500 mcg Methylcobalamine in the morning, 500 mcg Hexacobalamine at 2pm, 1000 mcg cyanocobalamine in the evening), to be honest the first days were very difficult: some symptoms were worse or new (very strong fatigue, tinglings, almost blind eye, etc.), some were better (less back pain). But I would say I was sicker than before.

This morning after 6 days I start to feel better (less fatigue and my back is less painful for the first time in 5 years) and I hope it will carry on improving :)

I advise you to carry on and hope you'll be better soon!

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Sorry it was hydroxocobalamine and not hexa.

The absorption and use and side effects (ex: acne for cyano) of the 4 different types of B12 are different. Scientifics suggest to take preferently Methylcobalamine and Adenosylcobalamibe in combination. You can have a look at this study: apotheekvanwambeke.be/sites...

I have not found Adeno yet, that is why I take a combination of the three others to start :)

I think prices are not so different.

Have a nice day!


Ok, so our scientists disagree? ^^

I think the best solution is to take a mix before research evolves so mistakes are limited, I take Methyl + Cyano + Hydroxo)


To be exact, it says (not in the abstract but in the core part) that best options are HCbl or MeCbl and AdCbl equivalently, and then Cbl

"Concerns have been raised regarding the stability of Cbl. It has also been said that Cbl should not be used in smokers as it has a cyanide moiety and smokers have an excess of thiocyanate in their blood, which can disturb the metabolism of Cbl and increase its excretion.17 Hydroxocobalamine (HCbl) is the form of vitamin B12 that lacks the cyanide moiety and has a hydroxyl group instead. Thus, HCbl may be a better agent to use in cases of B12 deficiency, especially in smokers.18,19 Another better option would be to give a combination of the active forms MeCbl and AdCbl"


Thanks for the replies I am going to get checked at gp and will update with my results, fingers crossed I get some answers 👍

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Hi Eaoz mine is pure MethylCobalamin, not sure if your reply was to me 🤔


Hi Health_hunter,

I think you should not take Methyl alone, according to studies you should take it with Adeno (or take Hydroxo or Cyano).

How are you now? Are you feeling better? I hope yes :)

It's been 12 days of supplementation for me and I still have muscular and joint aches, and strong fatigue. It looks like it's going to take time...

No anxiety or derealization/hallucinations for 12 days though, a record, I'm glad :)



Hi, i have just been informed that all my blood tests require no action all normal. I was told this over the telephone by the receptionist at go surgery. I am now baffled 🤔😩


Hi health_hunter.

Hopefully you’re still on the forum or managed to get to the bottom of your problems but if you had taken high doses of b12 and then had blood tests soon after it would have skewed the results considerably. Especially as serum level b12 doesn’t indicate active b12 levels (from what I’ve read)

Also never accept ‘normal’ from doctors surgeries. Ask for a printout of your results or ask for specific values and ranges over the phone. B12 has a ‘normal’ range of usually between 180-1000! Sometimes.

Usually anything below 4/500 can induce symptoms and if you are vegan /vegetarian you are almost certainly deficient or low.

It’s one of the most common deficiencies in vegans

Good luck


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